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0-30V Stabilized Power Supply
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| | |-+  0-30V Stabilized Power Supply
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audioguru
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« Reply #1274 on: February 24, 2012, 09:18:05 AM »

I know. I do not really need more than 20 volts, so I think a 24 volt charger fits my needs, could use this design with the charger I mentioned earlier?
The resistors and voltage drops all must be re-calculated to use a much lower supply voltage.
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xristost
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« Reply #1275 on: February 24, 2012, 04:25:45 PM »

I know. I do not really need more than 20 volts, so I think a 24 volt charger fits my needs, could use this design with the charger I mentioned earlier?

Part of the circuit will not work, because it use AC voltage to make negative supply voltage for U3. But charger will provide only DC voltage.
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audioguru
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« Reply #1276 on: February 24, 2012, 04:48:29 PM »

Part of the circuit will not work, because it use AC voltage to make negative supply voltage for U3. But charger will provide only DC voltage.
That is only one of hundreds of parts where the voltage is too low. What about the other hundreds of parts where the voltage is too low?
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du.facc
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« Reply #1277 on: March 04, 2012, 08:37:00 PM »

Can I add two potentiometers to the "fine tuning"? From what I know, just add the potentiometer in series with the potentiometer in the circuit that already exists, but do not know if this circuit is possible to contain the RV2 and RV3. If possible, which would then potentiometers?
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audioguru
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« Reply #1278 on: March 04, 2012, 10:49:49 PM »

A coarse pot and a fine pot would be a nuisance. The fine would almost always be in the wrong position.
Use a bigger knob instead on one pot.
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bugmenot
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« Reply #1279 on: March 14, 2012, 12:51:43 PM »

Or a multiturn pot.
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xristost
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« Reply #1280 on: March 14, 2012, 04:44:31 PM »

I finished my version of this famous project Smiley
Here how it looks like: http://diyfan.blogspot.com/2012/02/adjustable-lab-power-supply.html
You may also download PDF files of the project on that page.
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mikehZA
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« Reply #1281 on: March 17, 2012, 05:44:11 AM »

Hi,
Couple of questions regarding the negative supply:
Why is it required
Why only used on U3
Isn't there a lot of ripple on it?
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audioguru
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« Reply #1282 on: March 17, 2012, 08:13:30 AM »

Hi,
Couple of questions regarding the negative supply:
Why is it required
Why only used on U3
Isn't there a lot of ripple on it?
U1 has an output of +11.2V and its inputs are at +5.6V so it does not need a negative supply.
U2 has an output that goes as low as +1.0V and has inputs that work at 0V so it does not need a negative supply.
U3 is the current regulator. It works by reducing the output voltage so that the output current is what is set on the current-setting pot. In order to reduce the output current when the output is shorted then the output voltage of U3 must go to -0.7V because of the voltage drop across D9.
Then the output voltage can be reduced to 0V.

So U3 has a -1.3V negative supply.
I don't think the negative supply has much ripple because its load current is only a couple of mA. Besides, U3 is not affected by a little ripple.
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mikehZA
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« Reply #1283 on: March 19, 2012, 01:03:45 AM »

Thanks, Audioguru appreciate your clear answer.

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thenr.
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« Reply #1284 on: April 14, 2012, 01:34:45 PM »

I finished my version of this famous project Smiley
Here how it looks like: http://diyfan.blogspot.com/2012/02/adjustable-lab-power-supply.html
You may also download PDF files of the project on that page.

Hi,
i will use a power supply 24Vdc 3A instead of a Transformer. Can i eliminate the rectifier diodes, R2 e C2 ?
I didn't find MC34071, only MC34072. Can i change ??
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lighty
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« Reply #1285 on: April 14, 2012, 02:11:37 PM »

Hi,

I didn't find MC34071, only MC34072. Can i change ??

The MC24072 is a dual opamp configuration, it should work but its not a direct replacement part, as the pinout is different, but if you can work around this, then I'm sure you could.

PS, you will loose the offset too. but not a train smash though.

Thats just my opinion, perhaps wait for some  pro's to answer.
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audioguru
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« Reply #1286 on: April 14, 2012, 03:46:31 PM »

Thenr,
This project uses a 28VAC or 30VAC transformer. The rectified and filtered unregulated DC is +37.6V to +40.4V when the load is 3A, not just 24VDC. The circuit might need changes to operate from only +24V and the max output voltage will be about +18V or +19V.

Go to www.farnell.com and click on the flag of your country. They might have a warehouse full of MC34071 or TLE2141 opamps in your country.
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Tompa
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« Reply #1287 on: April 22, 2012, 01:15:45 PM »

Hello

I build modified version of this PSU... and i got 1 problem.... PSU worked fine untill today (when I put it inside the case/box)... something went wrong.. I cant regulate output voltage.. I got constant 36V.....

U2 is getting very hot after few minutes....


This is PSU when it worked... now is broken :/
http://vimeo.com/40025790

sry for my bad english...
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