0-30 Vdc Stabilized Power Supply

[ddav]

hi everybody

I used LM343( russian analog is K1408ud1, max power supply +-40v) instead of TL081. It works normally. And also R7 has reduced up to 0,22R and R18 has increased up to 82k.

[audioguru]

Hi Ddav,
Welcome to our forum. ;D
It is good that you found some high voltage opamps for good reliability.

[hana_moh]

thanks to the Boss "audioguru"
all is ok.

[audioguru]

Hi Hanna,
Your project looks nice.
I hope nothing blows up because the voltage of your 36V transformer is much too high.

[hana_moh]

thanks to you only LCD problem i will change as soon as possible
about "36 transformer is much too high" under test
thanks for interest and max follow up

[phaethom]

hello
i made thid power suply, but i just have a voltage between 0.43 and 19.98 volts
what can do?

[audioguru]

what can do?

Hi Phaethom,
Welcome to our forum. ;D

Did you make the original project or the modified one?
Did you substitute any parts?

1) What is the DC volatge across C1?
2) what is the negative DC voltage at pin 4 of U2?
3) What is the positive DC voltage at pin 6 of U1?

[phaethom]

i made by original project, and dont chage anything,
c1-33 volts
4-u2-(-4,6 volts)
6 u1 (10 volts)

sory but  my english is bad

[audioguru]

Hi Phaethom,
1) The voltage of C1 is low because a 24VAC transformer is 25VAC without a load and its peak is 35.4V. the rectifiers drop it to about only 34VDC.
2) Pin 4 of U2 has a 5.6V zener diode. Maybe you used one that is made for a high current, so its voltage is low in this circuit.
3) Pin 6 of U1 should be 11.2V but maybe you used a zener diode made for a high current so its voltage is low in this circuit.

Even with your low voltages, the output amplifier has a gain of 3.07 so your max output voltage should be near +30.7V, not just +19.98V. R11 and R12 determine the gain of the output amplifier. Check their values.

What is the part number of the 5.6V zener diodes that you used?

Without a load and with the voltage pot and the current pot turned to max, is the current-regulating LED turned on? What is the output voltage? What is the voltage at pin 6 of U2?

[phaethom]

now i have voltage between 21.7 and 31
zener part number is 2p d5

[phaethom]

suddenly my voltage on output is between 21.7 and 31

[audioguru]

Hi Phaethom,
I don't know your zener diodes.
I think your project has something loose inside.

[phaethom]

ok.
im gonna change it

[arman_linkin]

(exuse me for my bad english.i am only a  learner)
hi to all
I want to built this power supply.but I have a question :
1.if I use an ammeter for it ...it will show the ampere that the load use or the ampere that was set ?

thank a lottttttttttt.
Arman 

[phaethom]

i change zener diodes and the problem is the same (voltage on output is between 21.7 and 31 )

[Thomas]

1.if I use an ammeter for it ...it will show the ampere that the load use or the ampere that was set ?

The stupid thing will only show the current flowing trough it, but this hasn't always to be the current flowing trough the load :D
In plain: You can connect a switch across the output terminals of the project and produce a shortcut by pushing it. Then you can adjust the current limit, flick the switch back and use the project the normal way with the ammeter showing the current flowing trough the load.

[audioguru]

An ammeter in series with the load causes a voltage drop that ruins the excellent voltage regulation of the project.

Instead, connect the ammeter in series with the output transistors then its voltage drop is made-up by the circuit since it is inside the negative feedback loop. But maybe the voltage drop is high enough to reduce the max voltage output of the project at high current.

You can use a voltmerter to measure the voltage across R7 which is the current-sensing resistor, then calibrate it for amps.

You can also use a voltmeter to measure the voltage produced by the current-setting pot then calibrate it for the amps setting.

[arman_linkin]

The stupid thing will only show the current flowing trough it, but this hasn't always to be the current flowing trough the load :D
In plain: You can connect a switch across the output terminals of the project and produce a shortcut by pushing it. Then you can adjust the current limit, flick the switch back and use the project the normal way with the ammeter showing the current flowing trough the load.

beacause of my bad english...Icant understand your answer. i am also an amature in electronic.so please explain it more clear

Instead, connect the ammeter in series with the output transistors then its voltage drop is made-up by the circuit since it is inside the negative feedback loop. But maybe the voltage drop is high enough to reduce the max voltage output of the project at high current.

can you draw a diagram (or mybe a shematic) for me (about out put transistors)??????? :-*
i cant understand it.

You can use a voltmerter to measure the voltage across R7 which is the current-sensing resistor, then calibrate it for amps.

You can also use a voltmeter to measure the voltage produced by the current-setting pot then calibrate it for the amps setting.

and what is the range of each voltmeter????which of them show the current flowing trough the load.and which of them show the amps that was set with p2.
note : its not NOT NECESSARY for me to set current at special place.but it IS important for me to show the current flowing trough the load...

so help me please with diagram not with written message. :-*

I hope you apologize me for my gossips :-[ :'(

[audioguru]

Hi Arman,
An Amp-meter shows the current in the load.

Here is the schematic modified with an amp-meter in series with the output transistors so its voltage drop is made-up bu the circuit.

Or you can use Ohm's Law to calculate the voltage across R7. R7 is 0.47 ohms. 3A through 0.47 ohms produces a voltage across it of 3A x 0.47 ohms= 1.41V. Calibrate a voltmeter to show 0.3V when a voltage divider has 1.41V across it then the meter will show the load's current.

P2 is the current-setting pot. It is in series with R17 and R18 and they are fed from pin 6 of U1 which is 11.2V. When P2 is set for 3A it has 0.17V across it which can be amplified and fed to a voltmeter to indicate the current setting of P2.

[arman_linkin]

One more thing....I built this project and I tested it with 1A 24V trans(beacause I didnt have 3A Trans)but it doesnt worked correct.LED was always On and the out put voltagewas 0.41 V evev when I turn p1 and p2

[audioguru]

The original project might work with a 24V/1A transformer but its ordinary opamps will be operating with a supply voltage higher than their absolute max rating.

If the opamps survive then the low output voltage indicates that maybe a transistor or diode is connected backwards.

[AN920]

Shouldn't the ammeter be placed after point 3? That way all the current will go through the meter including transients from the output cap.

[audioguru]

I put the ammeter inside the negative feedback loop so its resistance doesn't ruin the very good voltage regulation of this circuit.

If the meter's resistance is 0.1 ohms then it would reduce the voltage 300mV at 3A if it was placed after point 3.

[AN920]

Good point.

[arman_linkin]

The original project might work with a 24V/1A transformer but its ordinary opamps will be operating with a supply voltage higher than their absolute max rating.

If the opamps survive then the low output voltage indicates that maybe a transistor or diode is connected backwards.

i check all of the diodes and transistors and ... but it steel doesnt work