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RobG

I've got the power

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I want to share some of the ways I am powering my projects and see if there are any other interesting ones that you could suggest.

 

Phone and computer accessory supplies, many of us have lots of them laying around. The best kind are the switchers, like the one from Zip drive (see picture.) Unlike the kind with transformer, they are light and small, and usually can be altered to output different voltage. I usually take them apart, but sometimes leave them in the case and remove line blades.

 

If you don't have any, this one on ebay is only $3.15 including s/h. It's small, 5V 2A, and you can get 3.6V by adding two diodes in series.

 

Another supply worth mentioning is this one, it's larger and more expensive, $8.88 (incl. s/h,) but it's much better quality.

 

If you have a supply but need to lower the voltage (for example you need 12V and 3.6V,) consider using DC-DC converter, like this one. At $0.79, it's a steal.

The same module is also available on ebay, 5pcs for $6, but they are used, pulled from equipment.

 

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post-197-135135502689_thumb.jpg

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I really like the one with the terminal blocks - had not seen that style before in such a tiny supply. I have a few of the one shown bottom left. They are held together with a single screw and usually no glue. Great if you want to mod it.

 

Many of these small regulated switching supplies use a TL431 (or clone) to set the output voltage. It is usually in a SOT-23 or TO-92 package. Find the TL431 and the two resistors that set the threshold voltage and you can easily convert a 5V supply to a 3.3V supply by changing one or both of the resistors. Some use a fixed Zener instead of the adjustable TL431. In either case it will be in series with the opto. Be aware that changing the output voltage may cause the ripple to increase and in some rare cases may make the regulation loop unstable.

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Are there any EE hobbyists who let wall warts go into the trash? I mean, I have, but only when pairing down to one box of them...

How can I put it in the trash? It goes to something around here. Now just which device did that come off of ? :?

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Here is my solution:

 

I finally managed to find some time to build a box to house an old AT style power supply. I now have +/- 12V, +/- 5V and 3.3V supplies on the front banana plugs. I'll add some labels later.

 

Front View:

Ps_front.jpg

Back view:

ps_rear.jpg

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As many people here have done I have also converted a PC PSU for use as a bench PSU. I only bothered with the +ve lines so far but the -ve wires inside are left long enough and taped off so I can add them at a later date if I feel the need.

post-1927-135135502706_thumb.jpg

 

For versatility though I also use MCP1702 LDO regulators so I can throw just about any voltage at it (upto 13.2V). They only need 2 external capacitors and they are good to go. These are handy as I can throw on some AA batteries (NiMHs can be used in groups of 3 directly though), 9V PP3s or wall-worts. I know the efficiency of the LDOs isn't great but for prototyping on breadboard the versatility of supply beats all the other considerations for me)

 

I have also been experimenting with Solar Cells though. I grabbed 2 (Garden Solar lights) from the poundshop. Two of the cells can power the MSP430 via the LDO using standard British sun (even on rainy days). Below is a picture of a solar powered clock I rigged up. As a proof of concept if works well :) however if there is even a short break in sunlight (clouds are ok but passing a hand past the cells isn't) then the MSP resets and the time is lost. When I get time I think I may look at using large(ish) caps to store charge for these dropouts. This will require a fair amount of research though as the analog side of things is my weak point at the moment.

 

Hope you found this interesting,

 

Dan

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I have also been experimenting with Solar Cells though. I grabbed 2 (Garden Solar lights) from the poundshop. Two of the cells can power the MSP430 via the LDO using standard British sun (even on rainy days). Below is a picture of a solar powered clock I rigged up. As a proof of concept if works well however if there is even a short break in sunlight (clouds are ok but passing a hand past the cells isn't) then the MSP resets and the time is lost. When I get time I think I may look at using large(ish) caps to store charge for these dropouts. This will require a fair amount of research though as the analog side of things is my weak point at the moment.

 

This should also be mirrored in the Projects section. Where did you get the cell from?

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This should also be mirrored in the Projects section. Where did you get the cell from?

 

The cells came from a rechargeable garden solar light..

 

Inside was a Solar Cell, a Bright White LED,an Inductor, an IC with 4 legs (mutated Transistor in appearance) that takes the 2V or so from the Solar Cell and charges the battery while there is sun and runs the LED by boosting and pulsing the power, and also a half length AA rechargeable battery marked with something like 80mAh (don't have the battery to hand so this is from memory)..

 

Poundland is a highstreet store that is a treasure trove of cheap Chinese tat to disassemble. Their Car Cig lighter socket power adapters/battery chargers have nice power regulation chips and the supporting components. Their frogs that make a croaking noise have an LDR (with leads about 3cm long) a speaker and a battery holder for 3x AG13 button batteries. Most of the stuff is through hole.. I guess cheap labour is cheaper than setting up a fab shop for most of this stuff...but there are some black blob items.

 

I think on my next visit I'll check out these little beauties... A wind up 430 has a certain steam punk charm to it :)

 

As to writing up my projects.. Thats "on my list".. Problem is Im having too much fun messing about with the actual doing to put time into the writing up and sanitising my code.. And my daughter was born 2 weeks ago so available time is ephemeral at the moment. Ooh.. and 200 RGB LEDs have just this minute arrived at my door :)

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