0-30V Stabilized Power Supply

[Tarkul]

Hey. Ive beentrying to fix the circuit. The problem now is that the ooutput voltage is steady at -0.5V!!! The good news is that the current limitng LED is now off... Voltage of D7 is -0.7V voltage of U2(out) is zero u3 is 32V and u1 is 8.3, D8 is at -5.6V.
Thanks a lot audioguru

[mendimano]

Hi Audioguru, as i sead earlier i have decided to build the modified version with this parts list and schematic, please if you have any new ideas and version to post it beafore i have start to buy parts, rgr

PS_Parts_List_10-11-09.pdf

[audioguru]

Hey. Ive been trying to fix the circuit. The problem now is that the output voltage is steady at -0.5V!!! The good news is that the current limitng LED is now off... Voltage of D7 is -0.7V

D7 is a 5.6V zener diode. Its voltage should be -5.6V so maybe you installed it backwards and maybe D5 and D6 are installed backwards.

voltage of U2(out) is zero

U2 will not work properly without a -5.6V supply. The output from U2 should go from about +1V to about +32V in your circuit.

u3 is 32V

It is low because your 24VAC transformer voltage is too low.

u1 is 8.3, D8 is at -5.6V.

The output of U1 should be +11.2V (the 5.6V from D8 times a gain of two). R4 should be changed to 1k.
D8 should be a 5mA zener diode (BZX79C5V6).

[effenberg0x0]

For the 3A version, R7 is 0R47 10W. I got 0R27 10W units. If i put two of them in series I get 0R54 and better heat dissipation (two components instead of one). But what would be the downsides?

[audioguru]

The original circuit with 0.47 ohms had a max current of about 4.1A which is too much for most of the parts.
With 0.54 ohms the max current before calibrating will be about 3.5A before calibrating.

[Tarkul]

Hey audioguru, i inverted de D7 zener, but still gives me bellow 1V. Maybe I ought to change the diode. Just one question. I had some 6A rectifying diodes, which I used for the rectifying part. Do you think this can be the source of the error? The diodes only say
6 A 4    
UTL
So Im not sure of their code.
Thanks again

[audioguru]

So Im not sure of their code.

Then throw them away and use good diodes that are very inexpensive.

[effenberg0x0]

The original circuit with 0.47 ohms had a max current of about 4.1A which is too much for most of the parts.
With 0.54 ohms the max current before calibrating will be about 3.5A before calibrating.

The original is 0R47 5W. Your's (fixed 3A version) is also 0R47, but 10W.
Do you think two 0R27 10W in series is still too little and risky?

Thanks,
Effenberg

[audioguru]

The original is 0R47 5W. Your's (fixed 3A version) is also 0R47, but 10W.
Do you think two 0R27 10W in series is still too little and risky?

The original circuit had many parts overloaded. For example its current was not calibrated so when set to max it was typically 4.1A (it could be higher if you have parts on the wrong side of their tolerance). So the poor little 0.47 ohm/5W resistor was dissipating 7.9W and was almost incandescent. If the current was calibrated for 3A max then the 5W resistor dissipated 4.23W and was still extremely hot.

Your 0.27 ohm resistors total 0.54 ohms and if the current is calibrated for 3a then each resistor dissipates 2.43W which is fine for a 5W resistor and is a waste for a 10W resistor.

[Tarkul]

Hey I'va tried to find the MC33071 and the TLE2141. The closest I was able to find was MC33171P and MC34002N. The first one is close, but has lower quality. Do you think this matters to much? It can handle the voltage levels required

[audioguru]

Hey I'va tried to find the MC33071 and the TLE2141. The closest I was able to find was MC33171P and MC34002N. The first one is close, but has lower quality. Do you think this matters to much? It can handle the voltage levels required

The MC33171 is low power so its bandwidth is too low for this circuit. The MC34002 has a max supply of only 36V which is too low and its inputs do not work anywhere near ground.

Digikey in Canada and the USA has 439 MC33071, 1323 MC34071 and hundreds of TLE2141 opamps in stock today.
Newark in Canada and the USA has 645 MC33171, 1024 MC34071 and hundreds of TLE2141 opamps in stock today.

Newark is now owned by Farnell who are in many countries.  Go to www.farnell.com and click on the flag of your country.

[Tarkul]

Newark is now owned by Farnell who are in many countries.  Go to www.farnell.com and click on the flag of your country.

I cant believe they have Chile Colombia and Puerto Rico, and not have Mexico.... Ill search it somewhere else

How about the MC34080BP? Im losing hope on the circuit. I think ill go with a more simple circuit involvoing one or more lm317k parallel to get 3A 1.27V-32V with no current limiter though...

[mendimano]

The MC33171 is low power so its bandwidth is too low for this circuit. The MC34002 has a max supply of only 36V which is too low and its inputs do not work anywhere near ground.

Digikey in Canada and the USA has 439 MC33071, 1323 MC34071 and hundreds of TLE2141 opamps in stock today.
Newark in Canada and the USA has 645 MC33171, 1024 MC34071 and hundreds of TLE2141 opamps in stock today.

Newark is now owned by Farnell who are in many countries.  Go to www.farnell.com and click on the flag of your country.

[audioguru]

I cant believe they have Chile Colombia and Puerto Rico, and not have Mexico....

Can you sneak across the border into the USA??

How about the MC34080BP?

Its inputs don't work when they are closer than 4V from the negative supply pin.

[Tarkul]

Can you sneak across the border into the USA??

jajajaja. Im actually going up north to USA.... Maybe there I can receive the chips
Do you know a good book in electronics? I've already taken circuit subjects(Circuits CA with complex numbers, frequency domain), but I don't know much about semiconductors in general.

[redwire]

Tarkul    Mouser is a large firm located in Texas.  They have plenty  of these chips. 

[Tarkul]

Tarkul     Mouser is a large firm located in Texas.   They have plenty  of these chips.   

Kool thx redwire

[Tarkul]

Someone should change the circuit in the page http://www.electronics-lab.com/projects/power/003/. They should put the version with the MC33071....

[audioguru]

The original version is still there so we can laugh at it.
I agree that the latest version should be added.

[Tarkul]

Hey I found another circuit much more simpler and powerful with voltage 0-30V and current limiter (not very exact) 0-6/8A, using lm317 and two 2N3055. NO OPAMPS... lol.

[audioguru]

An LM317 with only one type of  power transistor does not limit the current. A PNP transistor can be added to limit the current.

A current-limiter is not an adjustable current regulator.

[karthikeid]

for getting TLE2141 go to texas instruments website and free sample it will be mailed in four days....

[mendimano]

thanx for tip to get TLE2141, please if someone has build the 5 Amps version to post his experience,
first of all what kind of tansformer to use ( mine is 30 volt 8 amps) will it be enogh for 5 amps version

[audioguru]

If the transformer is 28VAC then its peak voltage is 39.6V. When the output of the project is 5A then the transformer must supply 39.6V x 5A= 198VA continuously. Then the 28vAC transformer must have a current rating of 198VA/28V=  7.07A.

A 30V transformer must be rated at 212VA and also must have a current rating of at least 7.07A.

[vacana]

which would be a good AC input fuse value for a 115V country?