Dual Lab Power Supply

[ante1]

Hi All,

I found an article about a Lab power supply. It

 

[audioguru2]

Ante,
That's a nice one.
In summer, I wouldn't want to be near it if it is supplying 5A at a low output voltage! Hot stuff.

 

[ante1]

audioguru,

Take a look at the power transistor data sheet. The SOA tells me they will cope as they work in pairs it is possible to get 0.1 V @ 5A with a good heatsink. Am I right?

Ante :

 

[Bikerman]

Hello

I'm new here, but I have been reading the forum for some time now (especialy about the 0-30 lab. PSU)

I just saw this, and it looks exiting.. how ever if someone desides to build it, there is a a drawing failure in the diagram!

Vcc on the opamp (pin7) should be connected to the "out" of IC1 (IC1's connection are also wrong, "out" is the case and "adj" is the leg).

R13, R14 (current set) and C7 should be connected to pin2 of IC2

 

[ante1]

Bikerman,

Yes, you are right . I found the original hand drawn schematic and this shows the correct connections to the opamp.
Thank you very much for this info.
Here is the hand drawn schematic:

Ante :

View attachment 35579

 

[darrins]

A few questions about this supply.

It has 2 primaries and 6 secondaries. Where do you find transformers like this? And why the need for all the secondaries?

A theoretical question: If you have a single set of AC leads split between two transformers, T1 and T2, will a load attached to T1 affect a circuit attached to T2? Assuming the same scenario (T1 and T2), would a load connected directly to the AC affect T1 and T2 circuits?

Thanks for posting this. I eventually want to make a custom power supply for my project. For now, I'm just using some 9V batteries as I discovered I was spending more time designing a power supply than designing my project.

Cheers.

Darrin

 

[audioguru2]

Hi Darrin,
Of course, the AC mains voltage will be affected a little bit when you add a load to it. The amount of voltage drop depends upon the length and quality of the wiring between the generating station and your circuit. But since the power supply is regulated, then it won't be affected.
I use an LM317 variable regulator circuit and rechargeable batteries for experimenting.

 

[darrins]

audioguru,

Do you have a schematic for your LM317 regulated battery charger?

I built my variable power supply using a LM317 (1.5 to 30V). Very similar in design to this one:

http://electronickits.com/kit/complete/powe/ck402.pdf

Perhaps my design could be modified to accomodate the battery charger?

Thanks.

Darrin

 

[audioguru2]

Darrin,
Nope, my rechargeable batteries have their own charger (the overnight kind) so I don't use the LM317 for charging.
It is difficult to make a fast charger for NI-CADs or NI-MH because you don't know how much charge remains.
There are charger chips available that detect the peak of the charging voltage, but they recommend a high-temperature and/or timer shutoff as a safety backup.

 

[MP1]

...It has 2 primaries and 6 secondaries. Where do you find transformers like this? And why the need for all the secondaries?

Darrin, in answer to your question, you can order different configuratuions of transformers from the manufacturer. However, on a hobbyist level, it would not be very cost effective for one off. You can use multiple transformers to achieve the same results and less cost.

MP

 

[ante1]

Darrin,

As MP mentioned it