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0-30V Stabilized Power Supply

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I am planning to use 24V/250VA transformer for this project, since this is the only one I have now. Is this ok? What is the difference if I use 10000uF instead of 12000uF for C1 (for 3A design)? Has anyone tryed to draw single-sided PCB for new 3A project?

PS: I drew PCB in Ki-cad. Can someone, please take a look at it and tell me if it's good? If it is, then others might use it too.

dokumentacija.zip

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I am planning to use 24V/250VA transformer for this project, since this is the only one I have now. Is this ok?

Then the output voltage at 3A will be only about 25VDC instead of 30VDC and when you turn the voltage-adjust knob higher then the output will not be regulated and will have lots of ripple.

What is the difference if I use 10000uF instead of 12000uF for C1 (for 3A design)?

You won't notice any difference. Big electrolytic capacitors have a very wide tolerance. The 10,000uF one might be 15,000uF and the 12,000uF one might be only 8,000uF.

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I am planning to use 24V/250VA transformer for this project, since this is the only one I have now. Is this ok? What is the difference if I use 10000uF instead of 12000uF for C1 (for 3A design)? Has anyone tryed to draw single-sided PCB for new 3A project?

PS: I drew PCB in Ki-cad. Can someone, please take a look at it and tell me if it's good? If it is, then others might use it too.


Yeah I did and you can download it from here, It's single sided and it can be 3A or 5A your choice

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What's the difference betwenn 3A and 5A projects. Something in the elements or the transformer?

The transformer must supply 28VAC at 200VA or 30VAC at 212VA.
There must be three output transistors with emitter resistors and a pretty big heatsink.
The heatsink for the driver transistor Q2 must be a little bigger.
The current sensing resistor R7 must be 0.27 ohms/10W.

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So, the PicMaster's PCB need a little change for the third transistor?


Yes it will require a little Mod, I only built the 3A version I've never really as the need for 5A, The mod is esy to do you can just hardwire the third transistor onto the exsisting tracs just solder the emitter resistor straight onto the pin of the transistor. I can mod the pcb to take the thr third transisor

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Here it is:


Looking at your PCB the output tracks are still not big enough to take the current for 5A and yes the pads need upgrading.

Here is the modified version this will either do the 3A or 5A version, For the 3A just leave out Q3A & R20A
For the 5A change R7 must be 0.27 ohms/10W (TB4 or the 2 holes either side), I have not updated the BOM yet but should be easy to workout

EL3-_5A_PSU.pdf

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How much VAa should be the transformer for 2x5A power supplies?

The peak voltage from the transformer is 39.6V from a 28V transformer and is 42.4V for a 30V transformer.
So 39.6V x 10A= 396VA and 42.4V x 10A= 424VA.

The windings must be completely separate if you are making a +/- power supply or if you are adding them to get up to 60VDC.
You cannot connect these power supplies in parallel.

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Hello, audioguru ,
I have one question
I have a two-winding transformer, rectifier whether the Department can use full-wave rectifier?
My English is poor, thanks for your answer ~


I do not know what you are asking.
Many transformers have 4 windings so they can be used with 115VAC or 230VAC and can be 15V at high current or 30V at lower current.

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A transformer either an inductor or an autotransformer.

You need a transformer with at least two windings (primary and secondary) for this project. Never use an autotransformer because it doesn't provide isolation form the mains.

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I do not know what you are asking.
Many transformers have 4 windings so they can be used with 115VAC or 230VAC and can be 15V at high current or 30V at lower current.


I did not express clearly
I have a two-winding transformer secondary, double winding with center tap voltage 2X25V, I can use full-wave rectifier rectifier? Means that this part of the rectification circuit using only two rectifier diodes, rather than the full-bridge rectifier
In addition, the circuit is able to use CA3140 LM741  operational amplifier?

post-60295-14279144281681_thumb.png

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I have a two-winding transformer secondary, double winding with center tap voltage 2X25V, I can use full-wave rectifier rectifier? Means that this part of the rectification circuit using only two rectifier diodes, rather than the full-bridge rectifier
In addition, the circuit is able to use CA3140 LM741  operational amplifier?

You are trying to make the original circuit that does not work properly and has many overloaded parts.
We fixed it and changed it and the new schematic and new parts list have been posted here many times.

Your 25VAC transformer produces a positive unregulated voltage of only 34VDC which is too low. Your supply will produce a maximum regulated output of pnly 26VDC at 3A, not 30VDC.
The new parts list has a 28VAC or 30VAC transformer and new 44V opamps. The new opamps work with no negative supply and a low voltage negative supply.

Your idea has a positive 34VDC supply and a negative 5.6V supply which is a total of 39.6VDC when there is a full 3A load and a total of maybe 43VDC when there is no load.
But the original TL081 opamps and the ones you are talking about have an absolute maximum allowed total supply of only 36VDC.

The new circuit has a positive supply that is +37.6V to +42.4V. It has a negative -1.3V supply for one opamp. Then its maximum total is less than the 44V max of the new TLE2141 or MC34071 opamps.
The old opamp and the opamps you are talking about do not work without a negative supply or a negative supply as low as -1.3V.


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I built it (3A version) and I have a few issues:
- current limiting LED is always on (if I turn current pot to max value it even lights more)
- I just can adjust minimum voltage to 50mV with voltage trimmer
- what can I adjust with other two trimmers?

However, PSU woks fine, the maximum output voltage with no load is 40V.

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