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Bortmoun

In need of a great bench power supply

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Hi there. I need a good bench power supply, which i want to build myself, for my hobby lab. The thing is, i have been thinking about LM-317 as my linear voltage regulator (and because here where i live i don't have no access to better ones). The design must have these features:

a)Current control from few mA to 5A

b)Voltage control from 0V to 30V.

For this purpose I've built this schematic, which i attached here. Please, tell me what you think about this project or if does work or does not, for i am a beginner in these things. R8 is just a dummy load.

The things i need help:

1) How can i add a minimum load (10 mA as by LM-317 datasheet) to keep the power supply operating in different potentials?

2) I need a replacement for 2n3822, i can't find it in my country too.

3) Can I run it from a fixed switched power supply (way more cheaper than buying a transformer here)?

4) In the future, I'm thinking about adding digital control with PWM to this circuit with Arduino or something like that. Do you think this is feasible?

Thanks in advance and sorry for my English.

PS: i have already looked here in this forum about the 0-30v power supply with op amps, but i really like the LM-317 concept, although i will build this last one if my project fails.

BS.png

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Every lab bench power supply that I am familiar with outputs only DC. The best power supply really depends on the application. What type of work or projects are you intending to use the supply for? I am most familiar with the Tek & Agilent supplies with 0–5v adjustable outputs and a 0–25v output. For hobbyist use, much more economical options can be found that would meet those needs.

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7 hours ago, davidjackson said:

Every lab bench power supply that I am familiar with outputs only DC. The best power supply really depends on the application. What type of work or projects are you intending to use the supply for? I am most familiar with the Tek & Agilent supplies with 0–5v adjustable outputs and a 0–25v output. For hobbyist use, much more economical options can be found that would meet those needs.

I'm intending to use it in low current projects like oscillators, arduino projects - these sort of things -  to learn electronic but also I'd love to drive fly-backs for juicier arks (which I've already done with my ATX power supply, of course with the standard measurements and personal protection to avoid electric shock),  and olds vacuum tubes. I could instead buy one here. But, for a reasonable price, I could only find Yaxun brand, which I don't take a lot of faith (the good one are like 3 or 4 times the price of these Chinese).

4 hours ago, Youkito1991 said:

Your project is good but when we use with big load ( big current) we waste a lot of power for heat from transistor.

I do not think I'll draw too much current from it often... So, this point can be left aside, but, yeah, you're right: by mine calculations, something about 7W per transistor will be lost upon high load.

 

15 hours ago, Bortmoun said:

The things i need help:

1) How can i add a minimum load (10 mA as by LM-317 datasheet) to keep the power supply operating in different potentials?

2) I need a replacement for 2n3822, i can't find it in my country too.

3) Can I run it from a fixed switched power supply (way more cheaper than buying a transformer here)?

4) In the future, I'm thinking about adding digital control with PWM to this circuit with Arduino or something like that. Do you think this is feasible?

The first question is crucial for my project!

Thank you for your reply!

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