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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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is there a way to increase the light of an LED with a dial?
I am trying to work out a way to increase the light intensity with a
dial for a regular LED from a dollar store flashlight. I don't know much about the LED since I can't see any markings. What would I need to buy from Radio Shack or an electronic store to do this? Thanks |
#2
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... I am trying to work out a way to increase the light intensity with a dial for a regular LED from a dollar store flashlight. I don't know much about the LED since I can't see any markings. What would I need to buy from Radio Shack or an electronic store to do this? Thanks You probably cannot increase it. Do you mean decrease the light? You could use a varible resistor to adjust the output to the LED. Mike |
#3
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is there a way to increase the light of an LED with a dial?
I guess I am looking for a dimmer or something for it - just a dial
that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! On Jan 22, 10:51 pm, "Michael Kennedy" wrote: "Victory" wrote in message ... I am trying to work out a way to increase the light intensity with a dial for a regular LED from a dollar store flashlight. I don't know much about the LED since I can't see any markings. What would I need to buy from Radio Shack or an electronic store to do this? Thanks You probably cannot increase it. Do you mean decrease the light? You could use a varible resistor to adjust the output to the LED. Mike |
#4
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is there a way to increase the light of an LED with a dial?
In article
, Victory wrote: I am trying to work out a way to increase the light intensity with a dial for a regular LED from a dollar store flashlight. I don't know much about the LED since I can't see any markings. What would I need to buy from Radio Shack or an electronic store to do this? Thanks A book on fundamental electronics. |
#5
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. |
#6
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is there a way to increase the light of an LED with a dial?
"James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike |
#7
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is there a way to increase the light of an LED with a dial?
"Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa |
#8
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is there a way to increase the light of an LED with a dial?
In article
, Victory wrote: I am trying to work out a way to increase the light intensity with a dial for a regular LED from a dollar store flashlight. I don't know much about the LED since I can't see any markings. What would I need to buy from Radio Shack or an electronic store to do this? Google on LED driver. That should keep you occupied for some time. ;-) If you wish to increase the brightness beyond that a constant current driver can do you'll be into a pulse circuit. -- *Sometimes I wake up grumpy; Other times I let him sleep. Dave Plowman London SW To e-mail, change noise into sound. |
#9
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is there a way to increase the light of an LED with a dial?
"Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa OK. I just tried it with a few bits that came to hand. White LED. 200k pot. 82k resistor. 2N3904 transistor. 12v supply. LED current adjustable from 0 - 25mA. You could also do it using an adjustable regulator as a constant current source. Arfa |
#10
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is there a way to increase the light of an LED with a dial?
Thanks for your help. Great to hear it worked. I don't want to go
above the brightness limit of the LED, so that shouldn't be a problem,. Now all of the parts you just listed, are they some of the things I can find at a local Electronic store, Radio shack or something I need to find online? Also, what kind of cost am I looking at here? OK. I just tried it with a few bits that came to hand. White LED. 200k pot. 82k resistor. 2N3904 transistor. 12v supply. LED current adjustable from 0 - 25mA. You could also do it using an adjustable regulator as a constant current source. Arfa |
#11
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is there a way to increase the light of an LED with a dial?
In article , Victory wrote:
I am trying to work out a way to increase the light intensity with a dial for a regular LED from a dollar store flashlight. I don't know much about the LED since I can't see any markings. What would I need to buy from Radio Shack or an electronic store to do this? Thanks You could buy one of the dollar stores lanterns with a variable output, and transfer the ckt. Its not going to fit inside the flashlight, but you might be able to size down the ckt. greg |
#12
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... Thanks for your help. Great to hear it worked. I don't want to go above the brightness limit of the LED, so that shouldn't be a problem,. Now all of the parts you just listed, are they some of the things I can find at a local Electronic store, Radio shack or something I need to find online? Also, what kind of cost am I looking at here? OK. I just tried it with a few bits that came to hand. White LED. 200k pot. 82k resistor. 2N3904 transistor. 12v supply. LED current adjustable from 0 - 25mA. You could also do it using an adjustable regulator as a constant current source. Arfa Parts values are not that critical. Any linear taper pot of around that value (150k, 200k, 220k, 470k), any resistor around that value (68k, 82k, 100k, 120k, 150k). Might be worth you getting a few resistors of around that sort of value, and just experimenting to see which one gives you best adjustment range with the pot value that you finish up using. The value of this resistor, along with the gain of the transistor, will determine the full on current through the LED. Start with the highest value resistor, and the pot turned right down to the ground end, and measure the current through the LED as you slowly turn up the pot. You don't really want more than 25mA through a standard white LED. The brightness did not increase much above about 18mA, with the example I tried. As far as the transistor goes, any general purpose NPN small-signal silicon transistor with a collector rating of 100mA or so, will be fine, so 2N3704 or whatever you can lay hands on. Any electronics component store should have these parts on the shelf. Prices are cents. In case you don't know how I hooked this up, it was fixed resistor top end to +12v, bottom end to the clockwise (from the front) tag on the pot. Anticlock tag of the pot to ground (supply "-") together with transistor emitter. Transistor base to centre tag of pot. LED anode to +12v. LED cathode to transistor collector. Measure current in LED by inserting milliammeter in series with LED ( meter "+" to +12v, meter "-" to LED anode. Arfa |
#13
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is there a way to increase the light of an LED with a dial?
It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Well I was assuming the original resistor was still in place, but yeah you do need it. |
#14
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is there a way to increase the light of an LED with a dial?
In article , Victory wrote:
Thanks for your help. Great to hear it worked. I don't want to go above the brightness limit of the LED, so that shouldn't be a problem,. Now all of the parts you just listed, are they some of the things I can find at a local Electronic store, Radio shack or something I need to find online? Also, what kind of cost am I looking at here? OK. I just tried it with a few bits that came to hand. White LED. 200k pot. 82k resistor. 2N3904 transistor. 12v supply. LED current adjustable from 0 - 25mA. You could also do it using an adjustable regulator as a constant current source. Arfa Well RS used to have stuff like that. Since they shut down my RS I don't get there much anymore. I still didn't hear a full purpose of this. The good dimmers use pulses to control brightness, much more efficient. The switched dimmer as seen on the $10 lanterns at the dollar store and K-Mart is really nice. I took one lantern apart last spring with the intentions of beefing up the LED's, but the driver circuit will only handle so much current. I still have one still intact. greg |
#15
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is there a way to increase the light of an LED with a dial?
On Jan 23, 2:09 pm, (GregS) wrote:
In article , Victory wrote: Thanks for your help. Great to hear it worked. I don't want to go above the brightness limit of the LED, so that shouldn't be a problem,. Now all of the parts you just listed, are they some of the things I can find at a local Electronic store, Radio shack or something I need to find online? Also, what kind of cost am I looking at here? OK. I just tried it with a few bits that came to hand. White LED. 200k pot. 82k resistor. 2N3904 transistor. 12v supply. LED current adjustable from 0 - 25mA. You could also do it using an adjustable regulator as a constant current source. Arfa Well RS used to have stuff like that. Since they shut down my RS I don't get there much anymore. I still didn't hear a full purpose of this. The good dimmers use pulses to control brightness, much more efficient. The switched dimmer as seen on the $10 lanterns at the dollar store and K-Mart is really nice. I took one lantern apart last spring with the intentions of beefing up the LED's, but the driver circuit will only handle so much current. I still have one still intact. greg Ok, thanks for that. Iam going to try and find a dollar store lantern like you said, although I don't recall seeing them anywhere of late. I guess variable brightness would be just as good for this project. |
#16
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is there a way to increase the light of an LED with a dial?
"Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. Mike |
#17
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is there a way to increase the light of an LED with a dial?
Actually, I only want ONE LED in what I am building, so I guess that
might check things a bit. Just one LED is all I need for this project. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. Mike |
#18
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is there a way to increase the light of an LED with a dial?
"Michael Kennedy" wrote in message . .. "Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. Mike Hi Mike. Well, if you reckon on a maximum current of say 20mA per LED, then for 3, that's 60mA. Depending on what rail voltage he's figuring on running it from, there's a good chance that if he was just using a pot on its own - even allowing for still using any original limiting resistor - that when he got towards the low end of his pot, he might be getting towards the dissipation limits of the track and the wiper structure. Most carbon track pots that you are likely to pick up at a 'general' electronics store, are only rated to a few mW, and are not designed to carry current. There are exceptions such as wirewounds, and some plastic tracked types. It just seemed to me that the addition of a 20c transistor guaranteed that the pot would not be damaged the first time it was turned up. Someone mentioned pulse drive, which is the better way to do it, both from linearity of control and LED life angles, but you are then into either a specialist driver IC, or something like a 555 timer IC and a couple of extra Rs and Cs and *still* the pot as well. Arfa |
#19
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... Actually, I only want ONE LED in what I am building, so I guess that might check things a bit. Just one LED is all I need for this project. You might get away with just a pot on a single LED. I guess for the cost of one, it's worth giving it a try, but it does depend to some extent on what rail voltage you are going to use to run it from, and the pot might not be too long-lived if it is going to be regularly turned up and down. If it's just a 'set and leave' project, you might be ok. Arfa |
#20
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is there a way to increase the light of an LED with a dial?
In article ,
Michael Kennedy wrote: It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. The 'usual' LEDs found can only be driven to about 30mA from a constant current source. So a 1/4 watt pot would likely be ok at the sort of voltages found in a torch. -- *The statement below is true. Dave Plowman London SW To e-mail, change noise into sound. |
#21
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is there a way to increase the light of an LED with a dial?
"Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. Mike Hi Mike. Well, if you reckon on a maximum current of say 20mA per LED, then for 3, that's 60mA. Depending on what rail voltage he's figuring on running it from, there's a good chance that if he was just using a pot on its own - even allowing for still using any original limiting resistor - that when he got towards the low end of his pot, he might be getting towards the dissipation limits of the track and the wiper structure. Most carbon track pots that you are likely to pick up at a 'general' electronics store, are only rated to a few mW, and are not designed to carry current. There are exceptions such as wirewounds, and some plastic tracked types. It just seemed to me that the addition of a 20c transistor guaranteed that the pot would not be damaged the first time it was turned up. Someone mentioned pulse drive, which is the better way to do it, both from linearity of control and LED life angles, but you are then into either a specialist driver IC, or something like a 555 timer IC and a couple of extra Rs and Cs and *still* the pot as well. Arfa I wasn't saying that your idea was bad, but just thought it might be a little over complicated considering the OP's apparent electronics knowledge. I agree that using a transistor would be best for reliability. The only reason I questioned you is that in the past I have used pots for exactly this, but then again that was before all of these high power blue / white LEDs exsisted too. |
#22
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is there a way to increase the light of an LED with a dial?
"Michael Kennedy" wrote in message . .. "Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. Mike Hi Mike. Well, if you reckon on a maximum current of say 20mA per LED, then for 3, that's 60mA. Depending on what rail voltage he's figuring on running it from, there's a good chance that if he was just using a pot on its own - even allowing for still using any original limiting resistor - that when he got towards the low end of his pot, he might be getting towards the dissipation limits of the track and the wiper structure. Most carbon track pots that you are likely to pick up at a 'general' electronics store, are only rated to a few mW, and are not designed to carry current. There are exceptions such as wirewounds, and some plastic tracked types. It just seemed to me that the addition of a 20c transistor guaranteed that the pot would not be damaged the first time it was turned up. Someone mentioned pulse drive, which is the better way to do it, both from linearity of control and LED life angles, but you are then into either a specialist driver IC, or something like a 555 timer IC and a couple of extra Rs and Cs and *still* the pot as well. Arfa I wasn't saying that your idea was bad, but just thought it might be a little over complicated considering the OP's apparent electronics knowledge. I agree that using a transistor would be best for reliability. The only reason I questioned you is that in the past I have used pots for exactly this, but then again that was before all of these high power blue / white LEDs exsisted too. No probs. It's just that I have used pots before in temporary 'power' lashup applications, and have found todays minuscule tracks to really not be up to the job. If the OP is just using say 6v worth of batteries - and he's gonna need at least 4 volts worth to run a white LED - then it would probably be OK, but the wipers on these modern pots are pretty delicate, and the contact area on the track is very small, so I just figured that even given his apparent limited electronic knowledge, a 'helper' transistor, which really is very simple to connect into the circuit, would be a good idea, if the scenario was that this thing was going to get turned up and down regularly. Arfa |
#23
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is there a way to increase the light of an LED with a dial?
"Arfa Daily" wrote in
: ..... No probs. It's just that I have used pots before in temporary 'power' lashup applications, and have found todays minuscule tracks to really not be up to the job. If the OP is just using say 6v worth of batteries - and he's gonna need at least 4 volts worth to run a white LED - then it would probably be OK, but the wipers on these modern pots are pretty delicate, and the contact area on the track is very small, so I just figured that even given his apparent limited electronic knowledge, a 'helper' transistor, which really is very simple to connect into the circuit, would be a good idea, if the scenario was that this thing was going to get turned up and down regularly. And the pots don't work so well, once you let out some of the magic smoke, as I have found out. -- bz 73 de N5BZ k please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. remove ch100-5 to avoid spam trap |
#24
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is there a way to increase the light of an LED with a dial?
In article , "Arfa Daily" wrote:
"Michael Kennedy" wrote in message ... "Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "Arfa Daily" wrote in message ... "Michael Kennedy" wrote in message . .. "James Sweet" wrote in message news:Y7Alj.8931$4b6.560@trndny08... "Victory" wrote in message ... I guess I am looking for a dimmer or something for it - just a dial that can turn the light up to full or down a little depending on what I want. But I want it to be controllable with a dial or something. I hope that is clearer. Thanks for the quick response and looking forward to the next one! You want a variable resistor. The value depends on the particular LED but you might try 2.5K or 5K. Yes, James ie right. You don't want a varible resistor like I said. You want a variable resistor. haha. I'm terrible at typing. Mike It may not work with a simple variable resistor because at higher settings, the current will increase enough to probably just burn out the small piece of the pot track that's still in circuit. A fixed resistor will also still be needed to limit the full brightness current. In order to get a decent control range, without risk of over-running the pot's track and wiper, I would suggest that a small transistor needs throwing into the mix to control the LED current, whilst the pot is left the low-current job of controlling the transistor's base. If I get time today, I'll give it a try. Arfa Arfa, How much current are we talking about here? If this is what I'm immagining in my head with 2 or 3 led's it shouldn't draw much power. I guess he could have one of those 5w led flashlights, but that was not what I had in mind when he said dollar store. Mike Hi Mike. Well, if you reckon on a maximum current of say 20mA per LED, then for 3, that's 60mA. Depending on what rail voltage he's figuring on running it from, there's a good chance that if he was just using a pot on its own - even allowing for still using any original limiting resistor - that when he got towards the low end of his pot, he might be getting towards the dissipation limits of the track and the wiper structure. Most carbon track pots that you are likely to pick up at a 'general' electronics store, are only rated to a few mW, and are not designed to carry current. There are exceptions such as wirewounds, and some plastic tracked types. It just seemed to me that the addition of a 20c transistor guaranteed that the pot would not be damaged the first time it was turned up. Someone mentioned pulse drive, which is the better way to do it, both from linearity of control and LED life angles, but you are then into either a specialist driver IC, or something like a 555 timer IC and a couple of extra Rs and Cs and *still* the pot as well. Arfa I wasn't saying that your idea was bad, but just thought it might be a little over complicated considering the OP's apparent electronics knowledge. I agree that using a transistor would be best for reliability. The only reason I questioned you is that in the past I have used pots for exactly this, but then again that was before all of these high power blue / white LEDs exsisted too. No probs. It's just that I have used pots before in temporary 'power' lashup applications, and have found todays minuscule tracks to really not be up to the job. If the OP is just using say 6v worth of batteries - and he's gonna need at least 4 volts worth to run a white LED - then it would probably be OK, but the wipers on these modern pots are pretty delicate, and the contact area on the track is very small, so I just figured that even given his apparent limited electronic knowledge, a 'helper' transistor, which really is very simple to connect into the circuit, would be a good idea, if the scenario was that this thing was going to get turned up and down regularly. Arfa I once put a reostat on a 6v lantern. It did save battery life. I did find out that the dimmer lamp worked better at shinning through the water at night, and full brightness just produced a glare. Yellow does not refract light like whiter light. Guess thats why fog lamps are yellow. greg |
#25
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is there a way to increase the light of an LED with a dial?
Ok, I did some tests, borrowing a variable resistor and it works great
- now here is the concern : I am not sure what the maximum output of the SINGLE LED is - so I am trying to match up the MAX of the variable resistor with the MAX of the LED, so it doesn't blow. The power sources is TWO button batteries : CR2032 (3V) ontop of each other to the LED. It works great. Now, when I add the resistor, how can I tell which VARIABLE RESISTOR to buy because I want one that is going to give me the maximum output (without it burning out) at the top of the resister cycle of turns (I guess the best example is 1-10 on a volume of a stereo because I am a non-techincal person when it comes to this stuff). So I want the resister to top out at '10' (brightest) but also be able to dim down (but it doesn't necessary have to go to 0). Thanks, I hope this is clear. On Jan 24, 12:42 pm, bz wrote: "Arfa Daily" wrote : .... No probs. It's just that I have used pots before in temporary 'power' lashup applications, and have found todays minuscule tracks to really not be up to the job. If the OP is just using say 6v worth of batteries - and he's gonna need at least 4 volts worth to run a white LED - then it would probably be OK, but the wipers on these modern pots are pretty delicate, and the contact area on the track is very small, so I just figured that even given his apparent limited electronic knowledge, a 'helper' transistor, which really is very simple to connect into the circuit, would be a good idea, if the scenario was that this thing was going to get turned up and down regularly. And the pots don't work so well, once you let out some of the magic smoke, as I have found out. -- bz 73 de N5BZ k please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. remove ch100-5 to avoid spam trap |
#26
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is there a way to increase the light of an LED with a dial?
If the batteries drive the LEDs directly, then there's no way that you can
burn them out by turning the pot all the way up -- in either case, the net resistance in series with the LEDs is zero. If there's a dropping resistor between the battery and the LEDs, the same is true, if you leave the resistor in place. |
#27
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is there a way to increase the light of an LED with a dial?
Ok, thanks for that. I just want to make sure I buy the variable
resistor that will work through the range the first time. I do not like taking things back if I don't have to... Does anyone know a part number for Radio Shack that will work with what I want? On Jan 24, 2:45 pm, "William Sommerwerck" wrote: If the batteries drive the LEDs directly, then there's no way that you can burn them out by turning the pot all the way up -- in either case, the net resistance in series with the LEDs is zero. If there's a dropping resistor between the battery and the LEDs, the same is true, if you leave the resistor in place. |
#28
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is there a way to increase the light of an LED with a dial?
Ok, I called Radio Shack and they have 'potentiometers', which I hope
is the same thing. I just don't know which to pick because the one they told me about is rated for 25 ohms... On Jan 24, 7:27 pm, Victory wrote: Ok, thanks for that. I just want to make sure I buy the variable resistor that will work through the range the first time. I do not like taking things back if I don't have to... Does anyone know a part number for Radio Shack that will work with what I want? On Jan 24, 2:45 pm, "William Sommerwerck" wrote: If the batteries drive the LEDs directly, then there's no way that you can burn them out by turning the pot all the way up -- in either case, the net resistance in series with the LEDs is zero. If there's a dropping resistor between the battery and the LEDs, the same is true, if you leave the resistor in place. |
#29
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... Ok, I called Radio Shack and they have 'potentiometers', which I hope is the same thing. I just don't know which to pick because the one they told me about is rated for 25 ohms... Yes a pot is a variable resistor. Don't they have something around 5K? That's a very common value. You can salvage this sort of thing out of all sorts of old junk. Any junky old boom box or other audio equipment will have a number of pots in it. Some are board mounted trimmers, some are panel mounted, they all do pretty much the same thing. If you get one with too low a resistance (25 ohms is too low) you won't be able to dim very far at all. If you go too high, only the upper portion of the rotation will be useful and below that the LED will be off. Anything from 1K-10K should be usable. Rat Shack used to sell an asortment of mixed trimpots for a few dollars, not sure if they still do. You might want to read up on this stuff so you understand the theory behind it rather than just asking for a specific part to get. Ohms law is really simple stuff if you understand basic algebra. |
#30
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is there a way to increase the light of an LED with a dial?
Darn, I just threw away a stereo a month or so ago. I will have to go
to Value Village or goodwill and see what they have. Will any stereo volume tuner do for a variable resistor? On Jan 24, 7:53 pm, "James Sweet" wrote: "Victory" wrote in message ... Ok, I called Radio Shack and they have 'potentiometers', which I hope is the same thing. I just don't know which to pick because the one they told me about is rated for 25 ohms... Yes a pot is a variable resistor. Don't they have something around 5K? That's a very common value. You can salvage this sort of thing out of all sorts of old junk. Any junky old boom box or other audio equipment will have a number of pots in it. Some are board mounted trimmers, some are panel mounted, they all do pretty much the same thing. If you get one with too low a resistance (25 ohms is too low) you won't be able to dim very far at all. If you go too high, only the upper portion of the rotation will be useful and below that the LED will be off. Anything from 1K-10K should be usable. Rat Shack used to sell an asortment of mixed trimpots for a few dollars, not sure if they still do. You might want to read up on this stuff so you understand the theory behind it rather than just asking for a specific part to get. Ohms law is really simple stuff if you understand basic algebra. |
#31
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... Darn, I just threw away a stereo a month or so ago. I will have to go to Value Village or goodwill and see what they have. Will any stereo volume tuner do for a variable resistor? Probably not the actual volume control, as this will have a log taper, which will bunch the control operation up one end, in this application. Tone controls should be fine. Arfa |
#32
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is there a way to increase the light of an LED with a dial?
Ok, I tried something with a 10K variable resistor today at a school
today (they were kind to indulge me). When I hooked up the 2 3V batteries in series to the resistor, it dimmed immediately when I turned it only slightly. The falloff of power to the LED went to the dimmest setting right away. On a whim, we hooked it up to 12V and the dimmer worked all the way through the entire turn. It was great. I am a little confused why this happened? The LED comes with 2 3V batteries in series from the $ store and is quite bright. When hooked up to the 10K resistor, it isn't as bright. So, the next basic question is - what happened? Should i get a resistor that is less than 10K? Thanks On Jan 25, 4:45 am, "Arfa Daily" wrote: "Victory" wrote in message ... Darn, I just threw away a stereo a month or so ago. I will have to go to Value Village or goodwill and see what they have. Will any stereo volume tuner do for a variable resistor? Probably not the actual volume control, as this will have a log taper, which will bunch the control operation up one end, in this application. Tone controls should be fine. Arfa |
#33
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is there a way to increase the light of an LED with a dial?
In article
, Victory wrote: Ok, I tried something with a 10K variable resistor today at a school today (they were kind to indulge me). When I hooked up the 2 3V batteries in series to the resistor, it dimmed immediately when I turned it only slightly. The falloff of power to the LED went to the dimmest setting right away. On a whim, we hooked it up to 12V and the dimmer worked all the way through the entire turn. It was great. I am a little confused why this happened? The LED comes with 2 3V batteries in series from the $ store and is quite bright. When hooked up to the 10K resistor, it isn't as bright. So, the next basic question is - what happened? Should i get a resistor that is less than 10K? LEDs are current driven. Which in practice means a different value resistor according to the supply voltage as you need to keep the current through the LED constant for the same light output. You can work out this series resistor value easily. The formula is:- Vs - Vf R = ------------ I Where Vs is the supply voltage, Vf the forward voltage drop of the LED and I the current in amps. You'd need to know the spec of the actual LED to be accurate but making Vs 3V and I 0.020A will do for most white LEDs. Which gives 150 ohms for 6 volts and 450 ohms for 12 The pot needs to go in series with a fixed resistor of the above value to set the maximum current - otherwise you could burn out the LED. The pot should be about 4 x the fixed resistor value to get a reasonably smooth dimming range. -- *Funny, I don't remember being absent minded. Dave Plowman London SW To e-mail, change noise into sound. |
#34
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is there a way to increase the light of an LED with a dial?
I forgot to add - with the 12v, the LED went all the way to it
brightest and dimmest while turning the resistor. It was perfect, but with the 5V, it peaked near the top of the resistors turn, and then started to burn out. Not sure why with 5V it would burn out, but with 12V it did not. On Jan 25, 7:29 pm, "Dave Plowman (News)" wrote: In article , Victory wrote: Ok, I tried something with a 10K variable resistor today at a school today (they were kind to indulge me). When I hooked up the 2 3V batteries in series to the resistor, it dimmed immediately when I turned it only slightly. The falloff of power to the LED went to the dimmest setting right away. On a whim, we hooked it up to 12V and the dimmer worked all the way through the entire turn. It was great. I am a little confused why this happened? The LED comes with 2 3V batteries in series from the $ store and is quite bright. When hooked up to the 10K resistor, it isn't as bright. So, the next basic question is - what happened? Should i get a resistor that is less than 10K? LEDs are current driven. Which in practice means a different value resistor according to the supply voltage as you need to keep the current through the LED constant for the same light output. You can work out this series resistor value easily. The formula is:- Vs - Vf R = ------------ I Where Vs is the supply voltage, Vf the forward voltage drop of the LED and I the current in amps. You'd need to know the spec of the actual LED to be accurate but making Vs 3V and I 0.020A will do for most white LEDs. Which gives 150 ohms for 6 volts and 450 ohms for 12 The pot needs to go in series with a fixed resistor of the above value to set the maximum current - otherwise you could burn out the LED. The pot should be about 4 x the fixed resistor value to get a reasonably smooth dimming range. -- *Funny, I don't remember being absent minded. Dave Plowman London SW To e-mail, change noise into sound. |
#35
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... I forgot to add - with the 12v, the LED went all the way to it brightest and dimmest while turning the resistor. It was perfect, but with the 5V, it peaked near the top of the resistors turn, and then started to burn out. Not sure why with 5V it would burn out, but with 12V it did not. On Jan 25, 7:29 pm, "Dave Plowman (News)" wrote: In article , Victory wrote: Ok, I tried something with a 10K variable resistor today at a school today (they were kind to indulge me). When I hooked up the 2 3V batteries in series to the resistor, it dimmed immediately when I turned it only slightly. The falloff of power to the LED went to the dimmest setting right away. On a whim, we hooked it up to 12V and the dimmer worked all the way through the entire turn. It was great. I am a little confused why this happened? The LED comes with 2 3V batteries in series from the $ store and is quite bright. When hooked up to the 10K resistor, it isn't as bright. So, the next basic question is - what happened? Should i get a resistor that is less than 10K? LEDs are current driven. Which in practice means a different value resistor according to the supply voltage as you need to keep the current through the LED constant for the same light output. You can work out this series resistor value easily. The formula is:- Vs - Vf R = ------------ I Where Vs is the supply voltage, Vf the forward voltage drop of the LED and I the current in amps. You'd need to know the spec of the actual LED to be accurate but making Vs 3V and I 0.020A will do for most white LEDs. Which gives 150 ohms for 6 volts and 450 ohms for 12 The pot needs to go in series with a fixed resistor of the above value to set the maximum current - otherwise you could burn out the LED. The pot should be about 4 x the fixed resistor value to get a reasonably smooth dimming range. -- *Funny, I don't remember being absent minded. Dave Plowman London SW To e-mail, change noise into sound. Well that formula explains it all. To put it in really simple but not completely accurate terms, the resistor drops the voltage actually going to the LED. The bigger the resistor the lower the voltage that reaches the LED. So if you put a larger resistor in series before the LED you need higher input voltage to achieve the same brightness because your output voltage to the LED would be lower with a larger resistor. If you check this whith a voltmeter while you are doing this it will be apparent what is happening. Higher voltage= brigher light. Higer resistance = lower output voltage and dimmer light. Does it make sense to you now? Mike Mike |
#36
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is there a way to increase the light of an LED with a dial?
Try this site:
http://led.linear1.org/1led.wiz If you don't know the diode(LED) forward voltage and current go to RadioShack and get a new one. The info is on the LED packaging and the website under Tech specs. for the Power supple voltage, if in series add the volts if in parallel its the mean(NOT RECOMMENDED to use more than one cell(battery), unless they are all the same) i.e. voltage, size and amount charged. or that more powerful battery will try to charge the others. http://www.radioshack.com/search/ind...rigkw=led&sr=1 In order to change or lower the brightness simply, take the output of the calculator measured in Ohms, and get a pot or (variable resistor) with the same value. that way you will get max power and brightness with your chosen LED. Hope this Helps Mark "Victory" wrote in message ... I forgot to add - with the 12v, the LED went all the way to it brightest and dimmest while turning the resistor. It was perfect, but with the 5V, it peaked near the top of the resistors turn, and then started to burn out. Not sure why with 5V it would burn out, but with 12V it did not. On Jan 25, 7:29 pm, "Dave Plowman (News)" wrote: In article , Victory wrote: Ok, I tried something with a 10K variable resistor today at a school today (they were kind to indulge me). When I hooked up the 2 3V batteries in series to the resistor, it dimmed immediately when I turned it only slightly. The falloff of power to the LED went to the dimmest setting right away. On a whim, we hooked it up to 12V and the dimmer worked all the way through the entire turn. It was great. I am a little confused why this happened? The LED comes with 2 3V batteries in series from the $ store and is quite bright. When hooked up to the 10K resistor, it isn't as bright. So, the next basic question is - what happened? Should i get a resistor that is less than 10K? LEDs are current driven. Which in practice means a different value resistor according to the supply voltage as you need to keep the current through the LED constant for the same light output. You can work out this series resistor value easily. The formula is:- Vs - Vf R = ------------ I Where Vs is the supply voltage, Vf the forward voltage drop of the LED and I the current in amps. You'd need to know the spec of the actual LED to be accurate but making Vs 3V and I 0.020A will do for most white LEDs. Which gives 150 ohms for 6 volts and 450 ohms for 12 The pot needs to go in series with a fixed resistor of the above value to set the maximum current - otherwise you could burn out the LED. The pot should be about 4 x the fixed resistor value to get a reasonably smooth dimming range. -- *Funny, I don't remember being absent minded. Dave Plowman London SW To e-mail, change noise into sound. |
#37
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is there a way to increase the light of an LED with a dial?
"Victory" wrote in message ... I forgot to add - with the 12v, the LED went all the way to it brightest and dimmest while turning the resistor. It was perfect, but with the 5V, it peaked near the top of the resistors turn, and then started to burn out. Not sure why with 5V it would burn out, but with 12V it did not. And exactly what led you (no pun intended !) to this odd conclusion? I can't think of any practical or theoretical reason why this should have been the case. 12v and full range control, yes, no problem. 5v, and range of control bunched up one end. Yes, no problem. Then it was "burning out" ? What was, the pot or the LED ? If the pot, then I don't know why it should have been giving trouble at the lower voltage rather than the higher, but it does rather neatly underline the problems that can occur when you use a simple pot to control DC, rather than adding a 'helper' transistor as I suggested *might* be a good idea. Arfa |
#38
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is there a way to increase the light of an LED with a dial?
At the highschool it was on one of those 'tester' boards with
different voltages and such. On Jan 26, 5:51 am, "Arfa Daily" wrote: "Victory" wrote in message ... I forgot to add - with the 12v, the LED went all the way to it brightest and dimmest while turning the resistor. It was perfect, but with the 5V, it peaked near the top of the resistors turn, and then started to burn out. Not sure why with 5V it would burn out, but with 12V it did not. And exactly what led you (no pun intended !) to this odd conclusion? I can't think of any practical or theoretical reason why this should have been the case. 12v and full range control, yes, no problem. 5v, and range of control bunched up one end. Yes, no problem. Then it was "burning out" ? What was, the pot or the LED ? If the pot, then I don't know why it should have been giving trouble at the lower voltage rather than the higher, but it does rather neatly underline the problems that can occur when you use a simple pot to control DC, rather than adding a 'helper' transistor as I suggested *might* be a good idea. Arfa '' |
#39
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is there a way to increase the light of an LED with a dial?
In article ,
"Arfa Daily" wrote: "Victory" wrote in message ... I forgot to add - with the 12v, the LED went all the way to it brightest and dimmest while turning the resistor. It was perfect, but with the 5V, it peaked near the top of the resistors turn, and then started to burn out. Not sure why with 5V it would burn out, but with 12V it did not. And exactly what led you (no pun intended !) to this odd conclusion? I can't think of any practical or theoretical reason why this should have been the case. 12v and full range control, yes, no problem. 5v, and range of control bunched up one end. Yes, no problem. Then it was "burning out" ? What was, the pot or the LED ? If the pot, then I don't know why it should have been giving trouble at the lower voltage rather than the higher, but it does rather neatly underline the problems that can occur when you use a simple pot to control DC, rather than adding a 'helper' transistor as I suggested *might* be a good idea. Arfa The reason I suggested the OP secure a primer on electronics is that, from his original post, and several subsequent ones, it's clear that he doesn't even know that ohms law exists. Look at the topic -- he wants to *increase* the brightness by adding resistance. When he says "burn out," he means that the LED is no longer illuminating. I wouldn't waste time with this guy, not because he's ignorant, but because he's clearly choosing to remain ignorant through laziness. |
#40
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is there a way to increase the light of an LED with a dial?
"Smitty Two" wrote in message
news When he says "burn out," he means that the LED is no longer illuminating. I wouldn't waste time with this guy, not because he's ignorant, but because he's clearly choosing to remain ignorant through laziness. I'd probably have written something like that, even just a few years ago, but my feelings have changed. It's too easy to forget how all of us were ignorant at one time. If you feel a poster doesn't deserve help, then don't respond. I'd like to offer the OP some advice, though... learn how to express yourself clearly. Your original post was atrocious, verging on the incoherent. I'd also suggest the OP buy one of those 100-in-1 electronic-experiment kits to play with. They're fun, and you'll learn something. |
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