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Smitjuh

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Posts posted by Smitjuh

  2. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    YES!!!!  ;D ;D ;D ;D ;D ;D ;D

    The thing works perfectly by now!!! It indeed was a short betwwen pin 6 and 7 a nasty one, but all short are nasty one's!  ;D ;D

    I can't thank you enough audioguru!! I will place pictures when it is in it's housing!

    one thing... what is the best place to add my amp, and voltage panel meters?

    greetz Tim

  4. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Output of U3 is 33,5 V. Values of R20 and R19 are like described in the project, 10k and 2,2k. So not wrongly painted, or got a alightly different color due to heat or something. I checked the PCB several times on shorts, but I can't find any.

    The 24V can be al bit more, I read it quickly on a analoge needle voltmeter... But when the load is on, and the current pot is turned counterclockwise, I can see my voltage build up when I turn the voltage pot. until about 30V and then the voltage drops (realy quick) to say 25, 26V

    Thanks again for the fast and good supply!!!

    Greetz Tim

  8. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hi audioguru,

    Here I am again  ;) I changed my op-amps to 44V rated ones (op37 from Analog) But With the last op-amps I could regulate from 0-32V, but now It is only possible to about 24V. And when the supply is powered for some time, the voltage decreases slowly. down to 22V.. When currents are flowing, it all go's wrong and my voltage drops dramatically. My LED still don't lights at any time...

  9. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hello! Audioguru!

    In your last post to me, Changing U2 and U3 was a option.. well, option it was nescesarry because they where working outside their workingvoltage. Well I changed them with LM741's. But there is no difference in the working of my powersupply.

    If I turn my Potentiometer P2 wholy clockwise, and I put a ballast on my output, my powersupply gives, lets say: 10V 1,5A.

    If I turn back  P2 (counter-clockwise) noting happens. Until the last part of the turnig cylcle... then the voltage fals down with about a 0,5V.. current remains the same.

  12. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hi!!

    I replaced some components with the better components mentioned by audioguru. The BZX zener and the both TIP31A's also some resistors. But my LED won't light!! The output from U3 (pin6) is 34V when pin2 is in voltage value above pin3 Pin6 remains 34V. but when I turn back P2, pin2 of U3 gets below pin3 and the ouput, pin6, is decreasing til say, 26V. Is this in theory enough to light the LED?

  13. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hi audioguru,

    I changed R4 to a 1K value, and my Voltage value has climed from 10.7 tp 11.2V!! I did not used the BZX zener, but this one will be delivered soon I hope. I looked at you're schmatic and see that the voltage acros R7 becomes 1,4V when there is a current flow of 3A.

    I tried it and what happens.... When I measure the voltage accros R7 when there is a current of 3Amp, the voltage is -1.4V!!!!!!! How can it become negative???

  14. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hi audioguru,

    reading this forum, you're the man for all my questions ... I think  ;)

    As entioned before in this topic, my current control circuit won't work properly. I will give some measurement results. On Pin 3 I can control the voltage from 0 to 1,7V (no load) witch is correct, because R18 forms together with P2 andR17 a resistor devider. At max, the next equation gives us: (10k/(56k+10K+33))*10,7=1,62V

    When I put a load on the circuit (Resistor) I can control pin # from -0,2 to 1,5V... Thats is already strange for me...

    The Base of Q3 has to become more negative than his emitter voltage so the trasistor can switch on, what lights the LED. To get the Base voltage far below 34V, pin 6 of U3 must get Low. This is only possible when Pin 2 of U3 becomes higher then pin3 of the op-amp. And here is the mystery.. pin 2 only gets lower when a current is flowing trough the shunt resistor R7!  ???

    What am I missing?? I hope someone can help me!! thnx in advance!

    post-14609-14279142524289_thumb.jpg

  16. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hi  audioguru,

    Thanx for the warm welkom  ;)
    I made the power supply with parts I still had in my hobby room. I created it in one weekend!
    But not fully working.. whats a shame.

    Pin 6 from U3 has a 33 volt potential. When I set pin 3 of U3 to 1V. as reference, what must pin 6 and pin 2 become? which values? My LED won't light... I checked all components in currentmaes. circuit. (resistors, Q3...) they look fine.

  17. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    Hi all,

    I made the power supply and it 'all' works. The supply delivers a 30V/3A supply! I can change the voltage, and I also can change the current, but not over the whole range. And the LED doesn't light on any time. I haven't tested anything (I'm not at home right now) but maybe someone can give me the solution because he is known with the problem.....

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