Can anyone help... (power supply project)

[steve_chew]

I got a project of power supply, can anyone help me... pls...

-Design and build a versatile power supply that will solve most of the supply problem arising in the everyday work of any electronic wrokshop. It should cover a wide range of voltages being continuously variable from 30V down to 3V. The output current is 2.5A maximum. The circuit should be completely stabilized even at extreme of its output range and is fully protected againsts short-circuit and overloading.

This is my project, pls help me ... thankx.....

 

[andrew2022]

https://www.electronics-lab.com/projects/power/003/index.html

 

[grrr_arrghh]

i doubt that anyone would mind helping, but it would be courteous if you admitted that it was a homework question. Your post gave the impression that it was a project you had set yourself - the text of the project makes it obvious that it is not.

 

[steve_chew]

Thanks for ur reply and help...

btw, there must be some misunderstanding here...
I was not purposely not to mention that is a 'homework' as u said, cuz in my U, we all call it project, group project actually...

Honestly, I'm really sorry bout that, cos it's my fault and I should say that is my homework....
really sorry bout that....
thanks for reminding me bout that....

 

[jepoi]

.....

try this site https://www.commlinx.com.au/schematics.htm

 

[grrr_arrghh]

I was not purposely not to mention that is a 'homework' as u said, cuz in my U, we all call it project, group project actually...

Honestly, I'm really sorry bout that, cos it's my fault and I should say that is my homework....
really sorry bout that....
thanks for reminding me bout that....

lol, no probs, theres no need to grovel, just a matter of courtesy to remember for the future, thats all.

 

[steve_chew]

need ur help again...

I tried to do the power supply as the following given website,
https://www.electronics-lab.com/projects/power/003/index.html

but it's really very hard to get the TL081 op-amp here, I searched for quite a long time, at last I got it. really quite many components cant get here...

but what I wish to know is, now I can't get the 24VA 3A output transformer, do I have any alternative??? maybe lower output current / higher ??

btw, for 100nF polyester, the boss said can use 104nF ceramic... can ??
and so with the 200nF polyester to 224 nF ceramic...

really curious to know that.... thanks again....

 

[Nigel Goodwin]

Re: need ur help again...

I tried to do the power supply as the following given website,
https://www.electronics-lab.com/projects/power/003/index.html

but it's really very hard to get the TL081 op-amp here, I searched for quite a long time, at last I got it. really quite many components cant get here...

Seeing as you don't have you location filled in, we've no idea where 'here' might be?.

But the TL081 is a very standard component, it should be freely available anywhere in the civilised world. If not, there are hundreds of other opamps you could use in it's place.

but what I wish to know is, now I can't get the 24VA 3A output transformer, do I have any alternative??? maybe lower output current / higher ??

Using a higher current transformer is fine, in fact it will help it run cooler, it's just a bit more expensive though.

btw, for 100nF polyester, the boss said can use 104nF ceramic... can ??
and so with the 200nF polyester to 224 nF ceramic...

really curious to know that.... thanks again....

104 isn't 104nF, it's 104pF - which is 100,000pF (the last number gives the number of 0's to add on the end), 100nF or 0.1uF - which is the correct value.

The 224 is 220,000pF or 220nF - which is a preferred value, whereas 200nF isn't, it should be fine!.

 

[audioguru]

Hi Steve,
Before getting ordinary parts for that Electronics-Lab power supply project, its designer had good ideas but screwed-up with its parts selection.
Many people over there have built it and have made changes to its parts list to make it work properly and reliably. They dicovered:
1) It can't produce anywhere near its rated 30V at 3A.
2) Its power transformer, output transistor, driver transitor and rectifiers overheat and fail.
3) Its main filter capacitor is much too small, so the output has lots of ripple.
4) Using a 24VAC/3A transformer, at no load the TL081 ICs which have an absolute maximum supply voltage rating of 36V, have 41V or more across them.

Go figure. A 24VAC/3A transformer is rated for a 72W load. 30V times 3A is 90W (which melts the output and driver transistors with a low voltage or shorted load) plus at least 16W to heat those transistors and rectifiers in addition to the load power. Therefore the 72W-rated transformer will have a load of 106W or more. It will overheat and will produce much less than 24VAC, which is much too small to get 30VDC output anyway.
Read all about the changes in their forum, here:
https://www.electronics-lab.com/forum/index.php?board=2;action=display;threadid=128

They have another forum to modify that power supply to get 30V at 5A from it:
https://www.electronics-lab.com/forum/index.php?board=13;action=display;threadid=196

 

[steve_chew]

thanks...
really learn a lot from u all....
Thanks....
:wink: