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0-30 Vdc Stabilized Power Supply


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Could you tell me exactly what I have to do modify in fayour of the max. 25V working? (R11 resistor? or the P2? or what?)

To allow you to calibrate its max output to 25.0VDC, add a 5k trimpot wired as a rheostat between U1 and P1. If the ripple is too high with a 25V/3A load then increase the value of C1 to 10,000uF and decrease the value of R15 to 100 ohms.
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We have tried the 0-30 V circuit and have a differnt problem.

1.At 26 Volts we are able to get 2 Amps constant output...but in between 26 -30 Volts we are able to get a current of 600mA - 100mA max.What is the reason any sugession please.

2. we ahve used a transformer sec., rated at 3 A max.

3. What modifications should we need to do to get a constant current of 3 A at 30 Volts.?

Please suggest its very urgent.

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Hi all,
can some one, specially circuit designer, give a complete part replacement?
new users (like me) can't read 70 pages?!

The circuit designer's list is the one that is in the project. The designer has made no changes. The list above are modifications suggested by a forum member.

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I did not know about the changings , i bought all the parts that were written , and i have found them with the exact rating , so should i buy again?

The 24VAC transformer is the most expensive part so keep it. Then the max voltage without ripple and with 3A load is about 24V. With a 3A load a 3A transformer is 41% overloaded since its output is rectified and filtered.

Replace the little 2N2219 that originally was Q2 with a real power transistor TIP31A with a real finned heatsink.
Replace the little rectifier diodes with a bridge rectifier module bolted to the metal chassis for cooling.
If the heatsink is big enough for the 2N3055 Q4 then since the voltage is low, second transistor in parallel won't be necessary.
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Actually i live in pakistan , and it is so hot out here , and about 40 degress , pure sun on your head . although the sho is nearby but the roads are always jammed and the traffic is like nonsense . and the local busses are full . it is cruel out here . and i don't have enough budget now also , so can i work around with these components as well .

Please pray for the weather , it's hell out there.

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Hi Faizan,

A 2SC1061 and hundreds of similar power transistors will work instead of a TIP31A. Maybe it is available in your country.

1N5408 diodes and any other 3A diodes will get extremely hot when the project has a 3A load.

The TL081 and most other opamps have an absolute max supply voltage rating of 36VDC. The project with your 24VAC transformer will have a supply voltage total of about 40VDC when it has low output current. A 741A opamp and a few others have a max supply voltage of 44V and the OPA445AP has a max supply voltage of 90V.

Your pcb mount screwdriver adjusted pot is a trimmer pot.

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