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#1
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dc to dc converter
I'm completely new to electronics so forgive my ignorance. I've read that
capacitors can be used to drop dc voltage, can they be used in the opposite way? can i build a dc to dc transformer that increases voltage while decreasing amperage with just capacitors and maybe transistors? I'd like to use some small solar cells to slowly charge a 5 volt super capacitor.. but ofcourse my cells only put out 4 volts in bright sunlight any help would be greatly appreciated. |
#2
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dc to dc converter
On Sun, 20 May 2007 15:38:06 -0500, Vampyre wrote:
I'm completely new to electronics so forgive my ignorance. I've read that capacitors can be used to drop dc voltage, can they be used in the opposite way? can i build a dc to dc transformer that increases voltage while decreasing amperage with just capacitors and maybe transistors? I'd like to use some small solar cells to slowly charge a 5 volt super capacitor.. but ofcourse my cells only put out 4 volts in bright sunlight any help would be greatly appreciated. You can use capacitors and transistors to boost voltage efficiently. Basically what you are doing is charging caps in parallel and reconnecting them in series before discharging them into the load. It is a very efficient way to step up voltage - but takes a lot of transistors and caps or an integrated circuit designed for the purpose. It is called "switched capacitor" voltage booster or converter. If you want to search it. All white leds require ~3.5 volts to light and single cells only put out 1.2 or 1.5 volts (sans lithium which puts out 3+) so there's lots of circuits for driving leds off low voltage. They would also be ideal to charge your super cap. Put in 3-4 volts and you will get out more than when you used just 1.2 volts. http://cappels.org/dproj/PulseBoostL...White_LED.html Shows a switched capacitor voltage booster using 6 transistors and no inductors. But inductors do the same job with fewer parts and still do it with good efficiency. It is far easier to use just a single transistor to charge a rechargeable battery from a solar panel using something called the "joule thief." The circuit is a blocking oscillator and uses inductive kick to raise the voltage a bit. I use one for some "garden lights" I built with 2 volt 100 ma solar panels. Open circuit the output of my 15 turn transformer is about 50 volts DC which is plenty to charge the 1.2 volt NMH battery. A second transistor uses the same panel to tell the oscillator to shut down when it is light out. Neat and as simple as it gets. You may need to protect the super cap from over charging with something like a zener diode to shunt XS voltage once the cap is charged. http://www.emanator.demon.co.uk/bigclive/joule.htm The original circuit http://www.joulethief.com/kit.php sells a kit using two transistors and a classic oscillator boost converter - schematic is on the site and can be built for $2-3 Their kit is only $10 http://www.cappels.org/dproj/ledpage/leddrv.htm Check out this site. Circuit is identical to the original joule thief, but he winds the transformer differently. Lots of tinker potential on this stuff. -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#3
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dc to dc converter
"default" wrote in message ... On Sun, 20 May 2007 15:38:06 -0500, Vampyre wrote: I'm completely new to electronics so forgive my ignorance. I've read that capacitors can be used to drop dc voltage, can they be used in the opposite way? can i build a dc to dc transformer that increases voltage while decreasing amperage with just capacitors and maybe transistors? I'd like to use some small solar cells to slowly charge a 5 volt super capacitor.. but ofcourse my cells only put out 4 volts in bright sunlight any help would be greatly appreciated. You can use capacitors and transistors to boost voltage efficiently. Basically what you are doing is charging caps in parallel and reconnecting them in series before discharging them into the load. It is a very efficient way to step up voltage - but takes a lot of transistors and caps or an integrated circuit designed for the purpose. It is called "switched capacitor" voltage booster or converter. If you want to search it. All white leds require ~3.5 volts to light and single cells only put out 1.2 or 1.5 volts (sans lithium which puts out 3+) so there's lots of circuits for driving leds off low voltage. They would also be ideal to charge your super cap. Put in 3-4 volts and you will get out more than when you used just 1.2 volts. http://cappels.org/dproj/PulseBoostL...White_LED.html Shows a switched capacitor voltage booster using 6 transistors and no inductors. But inductors do the same job with fewer parts and still do it with good efficiency. It is far easier to use just a single transistor to charge a rechargeable battery from a solar panel using something called the "joule thief." The circuit is a blocking oscillator and uses inductive kick to raise the voltage a bit. I use one for some "garden lights" I built with 2 volt 100 ma solar panels. Open circuit the output of my 15 turn transformer is about 50 volts DC which is plenty to charge the 1.2 volt NMH battery. A second transistor uses the same panel to tell the oscillator to shut down when it is light out. Neat and as simple as it gets. You may need to protect the super cap from over charging with something like a zener diode to shunt XS voltage once the cap is charged. http://www.emanator.demon.co.uk/bigclive/joule.htm The original circuit http://www.joulethief.com/kit.php sells a kit using two transistors and a classic oscillator boost converter - schematic is on the site and can be built for $2-3 Their kit is only $10 http://www.cappels.org/dproj/ledpage/leddrv.htm Check out this site. Circuit is identical to the original joule thief, but he winds the transformer differently. Lots of tinker potential on this stuff. -- Good advice but the most practical thing to do may be to just add a few more solar cells to your array. Jimmie |
#4
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dc to dc converter
On Tue, 22 May 2007 07:17:59 -0400, "Jimmie D"
wrote: Good advice but the most practical thing to do may be to just add a few more solar cells to your array. Jimmie All things considered, maybe. Lots of 4" X 4" solar panels are showing up in the surplus market with 2-4 volt outputs they put out about 50-100 ma and except for the voltage, could be useful for projects. $2-5 range prices and already waterproof. -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#5
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dc to dc converter
default wrote:
On Tue, 22 May 2007 07:17:59 -0400, "Jimmie D" wrote: Good advice but the most practical thing to do may be to just add a few more solar cells to your array. Jimmie All things considered, maybe. Lots of 4" X 4" solar panels are showing up in the surplus market with 2-4 volt outputs they put out about 50-100 ma and except for the voltage, could be useful for projects. $2-5 range prices and already waterproof. So, buy two of them and connect them in series. |
#6
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dc to dc converter
On Tue, 22 May 2007 10:28:30 -0400, John Popelish
wrote: So, buy two of them and connect them in series. Where's the fun in that? -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#7
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dc to dc converter
default wrote in
: On Tue, 22 May 2007 10:28:30 -0400, John Popelish wrote: So, buy two of them and connect them in series. Where's the fun in that? Wow thanks for all the great advice. I do agree though, where's the fun in that? hehe, I might just take that advice however and buy more solar cells for this project, but i still needed to grasp this bit of electronic skills, im gonna be off to experiment tonight with all of it, thanks alot to all who replied. |
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