0-30V Stabilized Power Supply

[dubok963]

Hello! ! ! I collected and I am this power unit
Image
Everything works, Restriction works BUT when I close probes under loading (KZ mode) the light-emitting diode lights up and at the exit there is no pure zero, and 0,5 0,7в. Tell, you have pure zero, or after all millivolts? I won't understand in what the reason, I assembled 2 blocks and on them at KZ there is no zero... http://www.youtube.com/watch? v=MvffSXU2... e=youtu.be


on the semisinmentnikakh I disconnected indication... I soldered directly on a payment lamp loading-2 consistently (I reduced loading wires to 1см, for this purpose to avoid wire resistance) I Wanted to deliver already to armor wire with a zero resistance...... I connected a multimeter in a mode of the voltmeter, minus a clip on the bottom leg of the shunt (a foot which on a minus goes), and a positive clip---directly on +выхода BP........ I close, the light-emitting diode lit up, and напруга 0,3....... 0,5 0,7.... and there has to be zero............... and with the second the block similarly, the pure zero isn't present............... details all new, KT827A,TL081, a konder after the rectifier 15000mkf 50v, SKF soldering gumboil, payments is washed by acetone......

Prompt in what a problem..... Maybe someone already faced it.... Thanks in advance

 

[audioguru2]

Sorry, I cannot understand your broken English. Russian?
Your youtube link does not work.

Do svidaniya.

 

[dubok963]

Yes, I from Russia.....
At short circuit "+" and "-" under loading protection joins, the light-emitting diode lights up, and tension has to fall to 0 volts, and at me it falls to 0,3 volts..... there is no pure zero..... How to correct it and to achieve chistono zero in a mode of "short circuit"? ? ?
Video

 

[audioguru2]

You are measuring the voltage drop across the resistance of the wires connected to your short circuit. Your voltage meter is connected to the output terminals of your project, not to the short circuit.
Try connecting a very thick wire with a short length directly between the output terminals of your project.

My very accurate ohm-meter measures its thick connecting wires to be 0.3 ohms when I press the probes together very hard. Then if there is 3A flowing, the wires will produce a voltage drop of 0.3 ohms x 3A= 0.9V.

 

[vakeiros]

Hi guys,

I'm from Portugal and just ordered all the parts for this project.

Tomorrow i'll receive the parts (hopefully) and start the project, i though start designing the PCB today but it's better to wait for the components and make it the right size holes.

I bought parts (not transformers) for build 5 of these and i'll build 1 first and see how it goes... i'll use a couple of 25V tranformers i have here sitting arroung because i'll need this mainly at 12v and if it's OK i'll build a double PSU with a 400VA 2*30v transformer and it will be my bench unit.

I'll start Aluminum anodizing and i'll need 4Amps regulated for some parts, i really hope this unit will fit my purposes

Well i'm really excited about this and i'll let you know as the project go long

best regards

 

[audioguru2]

Hi Vakeiros,
You can reduce the value of R7 to 0.33 ohms for a maximum output current of 4A but when the output voltage is low or is shorted then the driver and output transistors will get very hot.
For a 5A circuit we recommend using 3 output transistors (each with a series emitter resistor), then they share the heat.

With a 25V transformer you probably will not have an output as high as 30VDC when the current is 4A.

 

[vakeiros]

Hi Vakeiros,
You can reduce the value of R7 to 0.33 ohms for a maximum output current of 4A but when the output voltage is low or is shorted then the driver and output transistors will get very hot.
For a 5A circuit we recommend using 3 output transistors (each with a series emitter resistor), then they share the heat.

With a 25V transformer you probably will not have an output as high as 30VDC when the current is 4A.

HI AudioGuru, yes I know about that, I'd read most of this thread already.

To start I'll make one 3A with a 25V 100VA Transformer i have here sitting around and see how this PSU behaves, if i like it (I'm sure I will) I'll make a few more. For now I don't need 30VDC, only will need about 24-25V so the 25VAC will give me that I think.

I Know for the 5A I have to do a few changes (3*3055 with .33 resistor, lower sense resistor .27r, etc..) like i said, for now the 3A to start, then we'll see XD

thanks for the reply 

 

[rvendrame]

Hello gurus,

I will build one of these.  I have a toroid transformer of 28V  3A.  So I think I need to run it with maximum of 2A, in order to not overload the transformer, right?  And in this case the only modification would be increasing R7 to 0.67 ohms/10W?  And whould I keep the 2x 2n3055,  or just one with big heatsink will do the job?

Thanks!

 

[audioguru2]

Hello gurus,

I will build one of these.  I have a toroid transformer of 28V  3A.  So I think I need to run it with maximum of 2A, in order to not overload the transformer, right?  And in this case the only modification would be increasing R7 to 0.67 ohms/10W?  And whould I keep the 2x 2n3055,  or just one with big heatsink will do the job?

The 28V transformer produces a peak voltage of 39.6V. If the maximum output current from your project is 2A then the transformer must produce 39.6V x 2A= 79.2VA.
But the transformer is rated for 28V x 3A= 84VA so it will be very warm but be fine.

0.67 ohms is not a standard value, use 0.68 ohms for R7. Its max dissipation is 2 squared x 0.68 ohms= 2.72W. Use a 5W resistor.

The unregulated loaded voltage will be 39.6V - 2V - 1V= 36.6V. If the output is shorted at 2A then the output transistor (s) must dissipate 36.6V x 2A= 73.2W which is a lot for a single 2N3055 transistor even if it has a big heatsink but it will be fine if a fan is added. Use two output transistors on a pretty big heatsink without a fan. 

 

[thiagoas]

OK, now that I tested a little bit this power supply, I have some points.

BD139 don't get even warm, it was those shit 2n3055 overcharging him.
When I set, for example 1.5A limit, after a while that current starts going down, until it stabilize in 1.39A. What could cause that?
There is a display picture in the files on the first post of this thread, what project is that from?

thank you all guys ;D

 

[audioguru2]

OK, now that I tested a little bit this power supply, I have some points.

BD139 don't get even warm, it was those shit 2n3055 overcharging him.

The output transistors and the BD139 driver transistor get warm when they dissipate power. Power=  x voltagecurrent. So they heat when the current is high and the output voltage is low (because then these transistors have a high voltage across them).

When I set, for example 1.5A limit, after a while that current starts going down, until it stabilize in 1.39A. What could cause that?

If you set the voltage to 30V, set the current to 1.5A and have a 12 ohms load then the 30V across the 12 ohms would normally cause a current of 30V/12 ohms= 2.5A. but the current regulator causes the output voltage to drop to 1.5A x 12 ohms= 18V.

Since your current drops after a while then maybe the current sense resistor R7 increases its value when it heats (wirewound?). Or maybe your current-setting pot changes its value?

There is a display picture in the files on the first post of this thread, what project is that from?

The photo of the circuit board is this modified project and the pcb was designed and built by Redwire.

 

[thiagoas]

My pot is a 10-turn, I think it is OK.

R7 is wirewound, it varies the value with the increase of the temperature? What would be the most recommended?

 

[audioguru2]

My pot is a 10-turn, I think it is OK.

Yes, most 10-turns trimpots have excellent quality.

R7 is wirewound, it varies the value with the increase of the temperature? What would be the most recommended?

Yes, a wirewound resistor increases in value as it heats. Maybe yours is too small so it gets too hot? Maybe it is enclosed and gets hotter and hotter? Maybe it has poor quality?

 

[thiagoas]

I will make some temperature tests with it, and put something bigger if it doesn't work well.

Today I bought the case for the power supply, it's gonna look pretty.  ;D

 

[paul18fr]

Dear,

Where Can I find the latest release of the Power supply in those 125 pages (I mean the latest BOM, schematics and so on) ?

Thanks

Paul

 

[audioguru2]

There are a few threads about this project. The latest BOM and schematic are many years old and have been posted hundreds of times in the threads. A few pcb designs have been shown.
Recently a member organized these files and requested that a Moderator post them at the beginning of one of the threads but I don't think it happened.

I fixed the project but never built it. If I built it then I would have posted it as a new project.

I found it. Look at the reply from Peter K on August 15, 2014 in this thread.

 

[paul18fr]

Thanks for the quick answer (and for your contribution of course)

I'll have a look at the beginning of the threads

Paul

 

[liquibyte]

There are a few threads about this project. The latest BOM and schematic are many years old and have been posted hundreds of times in the threads. A few pcb designs have been shown.
Recently a member organized these files and requested that a Moderator post them at the beginning of one of the threads but I don't think it happened.

I fixed the project but never built it. If I built it then I would have posted it as a new project.

I found it. Look at the reply from Peter K on August 15, 2014 in this thread.

Thanks for the quick answer (and for your contribution of course)

I'll have a look at the beginning of the threads

Paul

Done.  See this Sticky.

 

[audioguru2]

Thanks, Liquibyte.
I hope you or Peter K will select and add one of the excellent pcb designs and place it in the sticky.

 

[liquibyte]

Thanks, Liquibyte.
I hope you or Peter K will select and add one of the excellent pcb designs and place it in the sticky.

I thought about that but how do I pick?  I didn't want to add mine because I thought it would seem pretentious to just put that one up.  I guess I should go through the thread(s) again and link them to the relevant thread plus include the files.  That may take awhile but I'll work on it.