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0-30V Stabilized Power Supply


redwire
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If you use the TL081 then you should use a low voltage transformer then the max output voltage from the project will be about 22V, not 30V.
Many of the parts will still get too hot.

We modified it so that the max output is 30V and it is reliable.


Hi there. I have followed this project for some time and while I think it is one of the better power supply circuits around (hence 35 pages of forum discussion on it), I am still confused as to what the actual outcome of all this discussion has been. I built one based on the circuit on the original site and of course it blew the guts out of the op-amps and I threw the rest away in disgust. Months later I found this forum and have read as much as I can of it without my eyes watering. There appear to have been several mods to the original circuit to lower the voltage to the op-amps, therefore saving their lives, and the authors claim the supply works OK, but then there are other rewrites of the circuit to use different op-amps, many of which can't be found locally, so I am at a loss which one to go for. On top of that, so many parts lists and circuits are bandied about here I don't know which goes with what and what version is the one to build. Can someone please summarise for me what the upshot of everything is and, if I was to build one tomorrow, which circuit and parts list would I be best to use. Thanks and sorry for being so lame.

Dave.
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Hi Dave,
The latest version uses a choice of two common and inexpensive opamps. Their max allowed supply voltage is 44V and they work with their inputs as low as the negative supply voltage. Their outputs go down to the negative supply voltage:
MC34071 opamp by Motorola, ON Semi or Freescale Semi.
TLE2141 opamp by Texas Instruments.

The opamps should be available almost anywhere (but not at Radioshack and maybe not in the country of Bangladesh).

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Hi Dave,
The latest version uses a choice of two common and inexpensive opamps. Their max allowed supply voltage is 44V and they work with their inputs as low as the negative supply voltage. Their outputs go down to the negative supply voltage:
MC34071 opamp by Motorola, ON Semi or Freescale Semi.
TLE2141 opamp by Texas Instruments.

The opamps should be available almost anywhere (but not at Radioshack and maybe not in the country of Bangladesh).


Thanks for the prompt and efficient replies Holt and Audioguru. If I understand your post correctly AG, the original circuit is fine as long as the hardier op-amps (and transistor) are used. Or, are you referring to the latest version as being the modified circuit referred to by Holt with those chips instead or the frail ones? I might just be building this over Easter I think....

PS. Apparently I live in a first-world country but nobody supplies these chips locally (and we have some very good components stores). I can get them by mail-order but otherwise they are not easily obtainable. Guess I'll have to go in another direction. Thanks anyway.
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Thanks again. I notice that earlier this year a guy named Ivan has added some suggestions to the bottom of the original circuit description page. He recommends adding a 7809 regulator and a zener to limit the voltage to the op-amps and connecting the relevant power pins and a couple of other circuit points to that new bus to reduce overhead voltage. In theory it sounds fine, though he also says to join 2 3055's with emitter resistors (which I have seen done in many other circuits) for current handling, because the single one got too hot. I don't recall anyone else mentioning this though.

The only reason I am stuck on using TL081s is because I cannot source any of those other op-amps from any of the suppliers I deal with. I might bread-board one up over the weekend using the 7809 idea and see how that performs; I'm not after something whizz-bang, so this might be good enough for what I want to do.

Thanks for your guidance and expertise.

Dave.

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Adding a voltage regulator might destroy the regulator because its input voltage might also be too high.
If the regulator survives then the max output voltage of the project will be reduced. Then you might as well use a transformer with a lower voltage.

All of the improved versions of this project use two 2N3055 output transistors to share the heat. They use emitter resistors so that they share the load even if their Vbe and hFE are different.

Where in the world are you where common inexpensive American opamps are not available?

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I'm in New Zealand and none of my usual component suppliers have those op-amps. Like I say, I can get them via mail-order but not in time for me to start building this weekend! I'll play around with the circuit as-is and see what happens while waiting for the op-amps to come from overseas.

Cheers

Dave.

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Farnell is in many countries including New Zealand. Today they have a few MC34071 opamps and many TLE2141 opamps in stock.

One of my suppliers is the Farnell in America called Newark. If I order before 8:00PM then it is delivered the next morning. I am in a different country (Canada)!

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I plan to use 4x2N3055 with 0R33 5W emitter resistor each, A 10A diode bridge, 2x10.000uF for C1, a 30V (2x16AWG) secundary for transformer,  a fan and 2x0R47 10W for R7. I'm waiting only for the TLE2141 samples from Texas Instruments. I think I'll get about 8-10A output?
The transformer come from a old PC AC stabilizer. I dismount and rebuild it for the PSU purposes.  I'll build the PSU in the case of the same PC AC stabilizer I got the transformer. I'm planning the panel.
Wat do you think about it Audioguru? Give me a light.  ;D regards.

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I have got an aircraft airbone  audio entertainment device, the current frequency of 400hz, Voltage 6 volts,can drive Well ?

This thread talks about the power supply project, not your entertainment device. Please start your own thread instead of hyjacking this thread. And please type in proper English because we do not know what you are asking.
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Hi!
If I use 3 2N5886 at the output, will Q2(BD139) and U2(MC34071) survive?  There is any circuit change to be made?

The calculations are simple so you should do them since you want to change the project.
1) Look on the datasheet of the 2N5886 transistors to see their minimum hFE at whatever max current you want. Divide the max output current by the minimum hFE to calculate the max collector current for the BD139.
2) Calculate the max power dissipation in the BD139 using the max collector current and its max voltage (when the output of the project is shorted). Look on its datasheet to see if it will survive the heat.
3) Divide the max collector current of the BD139 and divide it by its minimum hFE to determine the max current of U2.
4) Look at the datasheet of u2 and calculate if it will survive if it has the max calculatyed current and the max voltage in the circuit.
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Hi AudioGuru, I see the datasheet values for the transistores. With the "SC Analyser 2005", a Elektor Project, I read the Hfe of my 4 2N3055 and they are in the range of 159-180 Hfe under 2,5mA current test. It's right? Can you guide me to the right results to know if the redwire circuit will support 4x2N3055?
Thanks for your support too.
Erivanst, do you find the Atmega8 smd version for the LCD Multimeter?

post-47233-14279144130193_thumb.jpg

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With the "SC Analyser 2005", a Elektor Project, I read the Hfe of my 4 2N3055 and they are in the range of 159-180 Hfe under 2,5mA current test. It's right?

The two 2N3055 transistors operate at up to 1.5A each in this project, not only 2.5mA. You are probably just measuring their leakage current.
At 1.5A their minimum hfe is about 46 so the max current in the BD139 is 3A/46= 65mA.

Can you guide me to the right results to know if the redwire circuit will support 4x2N3055?

I don't know why you have four output transistors when only two are needed. Any of these power supply versions will work with many extra useless output transistors added.
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AudioGuru, I'm building the 5A version. therefore is the reason I want to put 3 or up to 4x 2N3055.
The measurements of Hfe of the four 2N3055 with the results of 159-180 Hfe where got under 2,5mA of current in the Hfe test. Under 1,5A of course the Hfe will be lower. But I don't know to make this conversion to have the results for the Hfe (159-180 Hfe - 2,5mA) under 1,5A.
I attached the SC Analyser 2005 project for information only.

SC_Analyser_2005.pdf

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