Friday, October 15, 2010

Adjustable power supply with LM317

LM317 is a cheap chip with 3 pins. It is widely known as one of the most basic microchip for adjustable power supplies. It is capable of working with 30 V and 1A current. However, it has quite a big voltage drop, around 1.5 Volts. Here is the pin out of the microchip:

LM317 comes in several packages, but TO-220 is the most convenient one, because you can easily get snap-on heat sinks for it.

The LM317 is not very good for "laboratory power supply" but for tests and troubleshooting it can go preety far.

This is the circuit that i have used to build one myself (note that this circuit is taken from original data sheet, but there is a mistake, pins 2 and 3 are swapped there. This is the right version!)
As you can see, there are only few components used.
1. LM317 microchip
2. 1uF electrolytic capacitor (The black stripe in circuit is anode (Negative; -))
3. 10uF electrolytic capacitor (The black stripe in circuit is anode (Negative; -))
4. 0.1uf ceramic capacitor
5. 240 (200 or 270 is also OK) ohm 0.125W resistor
6. 5K mono linear potentiometer
Optional parts:
7. Any LED.
8. 1k ohm 0.125W resistor

The pricing of all these things should be around 2$, or if you have resistors, capacitors and LED lying around it will be around 1$.
Sorry, but i wont be able to show you any photos if me making it - my camera is at the other town (im studying) at the moment, but heres a picture to see how small it actually is:
It is cheap, small, does not heat at all, but its hell useful! Try building one yourself!

36 comments:

  1. I always wanted to learn how to do this kind of stuff.

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  2. I dont get it. Too stupid for this... maybe. Well, rather too lazy to learn it.

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  3. wow, good tips... too bad i don't understand right now

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  4. I wish I could make this kinda stuff, hats off to you sir

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  5. I also always wanted to get into this stuff... thinking about building a reprap...

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  6. wow, I read this twice, and I'm starting to understand a little bit

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  7. Looks like the battery is the most expensive part.

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  8. that is very interesting man i like it

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  9. I like cheap chips, but when they cool down they don't taste so nice :X

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  10. so... what does it do? make energy?

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  11. keep more of these tutorials coming, there really good.

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  12. great post man i wanna read moar like this! ;)

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  13. whoa cool. I can sort of understand now that I'm getting further in my ece classes. awesome blog, you got a new follower!

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  14. Fascinating. What i'd really like to build is a synthesizer.


    +following this blog

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  15. very well ... I will try it myself ... thanks

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  16. I like it, gonna try it myself one day, when i've got money :(

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  17. will you do my electronic fundamentals coursework?
    its very basic compared to this :)

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  18. I need to make me one of these, thanks!

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  19. I can't even tin a wire properly yet.

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