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Timer Switch
Hi,
I have a camera hooked up to a 9v battery and want to be able to use a 'timer switch' to turn it on at a specific time ( like the ones you plug into a wall socket and then plug in your light socket and get it to switch your light on automatically at a certain time when your away ) Is there such a thing that can do this with a battery as the power source? Any help on this would be gratefully appreciated |
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Sean:
A couple of questions, Does this have to happen at a particular time of day? Or, four hours after you start the count down? And, Do you need an off time? Pat Ziegler Wholesale Electronics Inc. www.weisd.com wrote in message ... Hi John, Thanks for the reply. I'll better describe my situation. I have a 9v PP3 type battery which is connected to a pinhole camera. I want to physically connect the battery to the camera but I do not want the camera to consume the battery power until a set time during the day. So for example I connect everything together, set a timer to give power to the camera at a set time, maybe 4 hours later, so in 4 hours the timer gives power to the camera. That's basically what I wish to achieve. I have been to the RS site which has hundreds of 'timers' but as I have limited knowledge, I'm not sure what these things are, or if they are suitable, so any help and advice would be appreciated. Cheers, Sean On Tue, 28 Jun 2005 18:11:40 GMT, wrote: Hi, I have a camera hooked up to a 9v battery and want to be able to use a 'timer switch' to turn it on at a specific time ( like the ones you plug into a wall socket and then plug in your light socket and get it to switch your light on automatically at a certain time when your away ) Is there such a thing that can do this with a battery as the power source? Any help on this would be gratefully appreciated --- It's possible, but you'll need to specify how you want to start the timer, how long the delay will be until it turns on the camera, how long you want the camera to be turned on (as well as what you mean by "turned on". That is, is it a simple shutter release, is it a camcorder of some sort that you want to run for a while, or is it something entirely different) and anything else you can think of. Probably the best thing for you to do would be to describe your application, and that way we can fill in some of the blanks. |
I'm still confused. If you connect the battery to the camera will the camera start consuming power immediately, yes, the camera has no on/off, the battery is on a battery clip with a lead that fits into the camera's power socket, so the camera consume power once its all connected up. So, I need a timer switch in between the battery and camera to make the connection active at a specific time. camera (or do something else) to make it start consuming power? Also, once the camera starts consuming power from the battery do you want it to continue until the battery is depleted, or what? yes, i'm not bothered about the battery running down as it is rechargeable |
Sean:
A couple of questions, Does this have to happen at a particular time of day? Or, four hours after you start the count down? And, Do you need an off time? Pat Ziegler Wholesale Electronics Inc. www.weisd.com Hi Pat, I would like it at a set time during the day but I'm not bothered about an off time. Cheers, Sean |
On Tue, 28 Jun 2005 21:20:07 GMT, wrote:
I'm still confused. If you connect the battery to the camera will the camera start consuming power immediately, yes, the camera has no on/off, the battery is on a battery clip with a lead that fits into the camera's power socket, so the camera consume power once its all connected up. So, I need a timer switch in between the battery and camera to make the connection active at a specific time. camera (or do something else) to make it start consuming power? Also, once the camera starts consuming power from the battery do you want it to continue until the battery is depleted, or what? yes, i'm not bothered about the battery running down as it is rechargeable --- I suggest you use a mechanical timer like: http://www.grainger.com/Grainger/pro...686922&ccitem= or: http://www.grainger.com/Grainger/pro...mId=1611671503 -- John Fields Professional Circuit Designer |
Sean:
I am sure John will come up with a great circuit to do this. I might take the cheap way out and get an inexpensive digital alarm clock. disconnect the leads that go to the clock's noise maker. Use those leads to fire a latching relay. The output voltage from the clock would have to be known before choosing a relay. Assuming 12volts you could use an NTE RLYF1A012 this relay will only draw 12mA so should not overload the clock's output circuitry. You will want to add a resistor and capacitor across the relay's coil to keep it from cycling on and off as the clock pulses. 5,000 Ohms and 100mf in series across the relay coil will hold it closed ( assuming the clock pulses once per second). Once you turn of the alarm the relay will open in roughly 1/2 second. the relays switch contacts will supply the 9 volts from your battery to the camera. Pat Ziegler Wholesale Electronics Inc. www.weisd.com wrote in message ... Sean: A couple of questions, Does this have to happen at a particular time of day? Or, four hours after you start the count down? And, Do you need an off time? Pat Ziegler Wholesale Electronics Inc. www.weisd.com Hi Pat, I would like it at a set time during the day but I'm not bothered about an off time. Cheers, Sean |
--- I suggest you use a mechanical timer like: http://www.grainger.com/Grainger/pro...686922&ccitem= or: http://www.grainger.com/Grainger/pro...mId=1611671503 Thank John for your help. I think this will do the job. Cheers, Sean |
On Tue, 28 Jun 2005 17:09:14 -0500, "Pat Ziegler"
wrote: Sean: I am sure John will come up with a great circuit to do this. I might take the cheap way out and get an inexpensive digital alarm clock. disconnect the leads that go to the clock's noise maker. Use those leads to fire a latching relay. The output voltage from the clock would have to be known before choosing a relay. Assuming 12volts you could use an NTE RLYF1A012 this relay will only draw 12mA so should not overload the clock's output circuitry. You will want to add a resistor and capacitor across the relay's coil to keep it from cycling on and off as the clock pulses. 5,000 Ohms and 100mf in series across the relay coil will hold it closed ( assuming the clock pulses once per second). Once you turn of the alarm the relay will open in roughly 1/2 second. the relays switch contacts will supply the 9 volts from your battery to the camera. Pat Ziegler Wholesale Electronics Inc. www.weisd.com Thanks Pat for you help. Cheers, Sean |
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On Sat, 30 Jul 2005 12:49:55 +1200, Jasen Betts
wrote: In article , wrote: Hi, I have a camera hooked up to a 9v battery and want to be able to use a 'timer switch' to turn it on at a specific time ( like the ones you plug into a wall socket and then plug in your light socket and get it to switch your light on automatically at a certain time when your away ) Is there such a thing that can do this with a battery as the power source? a battery powered alarm clock with a few modifications could do that. what you'd need to do is remove the speaker and put a little amplifier in there to drive a relay. . . something like this maybe to supply +ve . R1 | . ,-[100k]-----+---+--- to relay . | .--+-|-' . | /' | D4 . 100p | |/' `-------- to relay . clock's o--||-+---+--[10k]-(-----| BC549 . speaker terminals | `-||-+--' |\| . o--. `-[100K]--| ~~\ . | | `| . diodes are 1N914 etc `------------+----||-||-+---- to supply -ve . except D4 which is 1N4001 or similar . supply voltage should be chosen to suit the relay. R1 may need to be increased. at the point labeled ( the wires cross. no guarantees but it should work... --- Redrawing your circuit for clarity, here's what you're advocating: +V | +--------+ |K | [1N4001] [COIL] | | +------[100K]------+--------+ | | | C IN---[100pF]--+----|----+--[10K]-------------B | | |K E [100K] | [1N914] | | | | | IN------------+----+----+--[1N914]--[1N914]--+ | GND which makes no sense, to me. Would you please explain how it's supposed to work? -- John Fields Professional Circuit Designer |
In article , John Fields wrote:
On Sat, 30 Jul 2005 12:49:55 +1200, Jasen Betts wrote: In article , wrote: Hi, I have a camera hooked up to a 9v battery and want to be able to use a 'timer switch' to turn it on at a specific time ( like the ones you plug into a wall socket and then plug in your light socket and get it to switch your light on automatically at a certain time when your away ) Is there such a thing that can do this with a battery as the power source? a battery powered alarm clock with a few modifications could do that. what you'd need to do is remove the speaker and put a little amplifier in there to drive a relay. . . something like this maybe to supply +ve --- Redrawing your circuit for clarity, here's what you're advocating: actually no.. the 100k goes between the series diodes and the +V like this: +V .. | .. +--[100K]----------+--------+ .. | |K | .. | [1N4001] [COIL] .. | | | .. | +--------+ | | | C IN---[100pF]--+----|----+--[10K]-------------B (NPN) | | |K E [100K] | [1N914] | | | | | IN------------+----+----+--[1N914]--[1N914]--+ | GND which makes no sense, to me. Would you please explain how it's supposed to work? the two 914 diodes in series bias the transistor right to the edege of its conducion region, the capacitor and the third 1N914 diode form a diiode pump that'll push it over the edge into conduction in the presence of an small-ish AC signal of a few hundered milivolts.. like a battery clock would use to power a piezo chime... that's my thinking anyway, the 1N4001 is a freewheeling diode to protect the transistor. on second though that top 100K should probably be a 10K Bye. Jasen |
On Sun, 31 Jul 2005 23:14:58 +1200, Jasen Betts
wrote: In article , John Fields wrote: On Sat, 30 Jul 2005 12:49:55 +1200, Jasen Betts wrote: In article , wrote: Hi, I have a camera hooked up to a 9v battery and want to be able to use a 'timer switch' to turn it on at a specific time ( like the ones you plug into a wall socket and then plug in your light socket and get it to switch your light on automatically at a certain time when your away ) Is there such a thing that can do this with a battery as the power source? a battery powered alarm clock with a few modifications could do that. what you'd need to do is remove the speaker and put a little amplifier in there to drive a relay. . . something like this maybe to supply +ve --- Redrawing your circuit for clarity, here's what you're advocating: actually no.. the 100k goes between the series diodes and the +V like this: +V . R1 | . +--[100K]----------+--------+ . | |K | . | [1N4001] [COIL] . | | | . | +--------+ | | | C IN---[100pF]--+----|----+--[10K]-------------B (NPN) | | |K E [100K] | [1N914] | | | | | IN------------+----+----+--[1N914]--[1N914]--+ | GND which makes no sense, to me. Would you please explain how it's supposed to work? the two 914 diodes in series bias the transistor right to the edege of its conducion region, the capacitor and the third 1N914 diode form a diiode pump that'll push it over the edge into conduction in the presence of an small-ish AC signal of a few hundered milivolts.. like a battery clock would use to power a piezo chime... that's my thinking anyway, the 1N4001 is a freewheeling diode to protect the transistor. on second though that top 100K should probably be a 10K --- 1. Since this thing is supposed to be battery operated, I'd be a little reticent to use your biasing scheme since it throws away power. Using a 2N4001 for the transistor and 100K for R1, the quiescent current being drawn from a 9V supply is 1.05mA. Reducing R1 to 10K increases the quiescent current to 5.38mA. 2. Since you have nothing to store charge, the 100pF cap is going to act like a differentiator and push charge into the transistor's base on the rising edge of the alarm signal but, on the falling edge, it'll pull the base as negative as the third diode will let it go, so the relay may never get a chance to make. A conventional charge pump would look something like this: IN--[C]--+--[DIODE]--+----DC TO LOAD |K |+ [DIODE] [CAP] | | IN-------+------------+ 3. Assuming that the clock's alarm signal is a 1V, 1000Hz square wave with pretty crispy edges means that, if it's feeding a 10000 ohm base resistor, the signal going into the base will be a positive-going spike with a time constant of about 1 microsecond. That means that if the spike rises to 1V initially, 1µs later it'll be at about 330mV. Since you have the transistor conducting slightly with your bias network and the alarm signal cap-coupled, you'll probably be able to pump a little current into the base even ten time consytants downstream, but that still leaves you with no signal going into the base for 90% of the time, so there's no way the relay's going to be made looking at that kind of a duty cycle. As if that wasn't bad enough, there's the problem of drive. If we assume that we can get 1V excursions from the alarm, we'll be driving 1V into the 10k ohm base resistor, which means a base current of 100µA on top of the 5µA or so that's already flowing in there from the bias network, so even if you use a sensitive reed relay that only needs 10mA of current to make it work, the transistor would need to have a beta of 100 or so. If it was a steady DC it might work, but I'd prefer to force the transistor to a beta of ten to make sure that everything is nice and saturated. So what's the solution? It's hard to say because the OP hasn't stated whether he wants to take a single picture or several over a period of time, but I've posted a general scheme which might work to abse under "Alarm clock interface" For battery use I'd switch the comparators to micropower and change some component values and, depending on what the OP wants, maybe make some circuit mods. -- John Fields Professional Circuit Designer |
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