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0-30V Stabilized Power Supply


redwire

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redwire - thanks for the tip. I saw the additional options but didn't open it. I was looking in the icons above the message box.

You presumably have built this PSU. When I eventually get around to routing the PCB and buying the TXs are there any points to look out for ?

I noted in the list of components that some of the specifications are short - i.e. diode bridge should be rated at the full load current and the output driver transistor will probably have to be mounted on a heatsink as the base current to the output TR's will be high (hfe low on these output TR's).

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When I eventually get around to routing the PCB and buying the TXs are there any points to look out for ?

You should be aware of the footprints of some of the capacitors and the trimpots, i am using an offprint bridge rectifier, because i am going for the 5A version, and i had an 35A rectifier, perhaps a little overkill, but i had it.
i havent finished the psu yet, but should be able to do a test in a couple of days, i am mounting Q2 offprint aswell, i have made the cabinet of aluminium, so i will just mount it at the bottom plate

Holt
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Well- i have made a small test, and it seems to work, the only thing not working is RV1 who has no effect at all, not that it matters, the voltage is 0 when turned down, but no adjustment possibel. i have measuret the voltage on pin 1 and pin 5 on U2, and it dosent vary when adjusting RV1.
It seems that the voltage is occilating a bit, but it can be my voltmeter playing tricks on me.
I will put it all together in the cabinet and make some more tests

Holt

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GrahamG.    I built the original, and at the least 2 revisions.  I didn't build cases for each but I did temporarily test them with a load.      For the 5A version, I would definately mount the rectifier to the case for maximum heat disipation.  The PCB will work fine just use wires to connect to the holes.  For the on board rectifier, I found some nice heat sinks from some old computer power supplies .  With a small cut along the bottom of the heat sink, it fits nicely on the pcb and works fine for 3A (still gets pretty warm). 

The main thing is to insure your diodes are oriented in the correct direction.  Also a large number of builders connect the BCE terminals on the transistors incorrectly.   

I think the easiest thing would be to convert the double sided Eagle  board to a single.  There will probably be a few jumper wires but it would be easier than ensuring that all vias are found and connected.    That can be done in the autorouting routine.  Of course wire sizes would need to be re-adjusted  but there are only a few that require thicker traces. 

I think most builders have noticed that RV1 does not have much affect.  I believe that C7 bleeds some voltage and the change from a negative -5.6 to -1.3 negative rail may have an effect.      I think you will find that if you have at least some small load the power supply will drop to zero when turned completely down. 

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redwire - thanks fo ryour feedback.

That can be done in the autorouting routine.


I prefer not to auto-route on Eagle as I dont like the way it places tracks. A double sided is fine for me as I just use jumpers for the top layer, adjusting the via diameter for current.

The main thing is to insure your diodes are oriented in the correct direction.  Also a large number of builders connect the BCE terminals on the transistors incorrectly.
 

Noted on your heatsinks and wire sizes, and diode and ECB orientation. I am an electronic engineer and know about this. Overlooked very easily!

I have not checked the circuit out but I hear what you say about RV1. What was it "supposed" to adjust ?
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If C7 (the output capacitor) is an electrolytic type then it has "dielectric absoption" where it stores a charge even if it is shorted. Then the output always has a voltage even if the voltage pot is turned down. It also messes up the setting of RV1 that should adjust the output offset voltage about plus and minus 50mV so that it is 0V when the voltage setting pot is turned down.

If C7 is changed to a film capacitor then the dielectric absorption problem will disappear.
A 10uF film capacitor is pretty big.

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I built the original version about two years ago ( with the Voltmeter + Ammeter LCD panel ) and it works wery good, but now i need some more power and i decided to built the new version with the 5 A output ( it is possible to become 7A with more powertransistors ? I have a 30V~ / 10 A trafo ). I used EAGLE ( i don't make publicity for EAGLE !! ) to make a single PCB layer with only 3 wire on top of PCB. The C1 ( 2x10.000

30V_5A_PSU_Eagle.zip

Pictures.zip

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tesseract

Brilliant. I think you are the first person that I have seen on this forum who has actually built the unit and made the associated comments about various parts that need to be changed or put off the PCB.

Did you suffer from this 0V adjust problem with the original cct or is it just the newer version that does this ?

Nice to see also that someone has published the EAGLE CAD files. A great help.

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The PSU are not ready because i have problems to become the TLE2141 in Germany.

You can get them here: http://de.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6612000 or you can order samples from TEXAS INSTRUMENTS like i did, ordered them sunday and got them tuesday- pretty fast from USA to Denmark.
I dont know if it is possibel to buy from RS in Germany unless you are a registret compagny, it isent in Denmark, thats why i orderet the samples
If only you had postet the PCB design 2 weeks before, it was just what i was looking for, its looking really good :D

Holt
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I dont know if it is possibel to buy from RS in Germany unless you are a registret compagny.


Yes you have right, that is my problem, RS sell only to a company. But i found someone and he ordered it for me. I must wait only a few days and i have the parts.
You have right it is possible to rotate D9 and eliminate the wire, but it does not change much....

@GrahamG
i check the old version of PSU and and it is possible to adjust the voltage up to 0.0 volt.
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@audioguru,
I'll give you absolutely right, it may be the original PSU has errors, but i built it for about 2 years ?? ( with TL081, 1x2N3055 and i have used the shown PCB ) and it's work fine !

In addition to the errors of the offset adjustment, the opamps are operating at supply voltages above their absolute maximum allowed voltage, the transformer and many resistors are overloaded at full output, the tiny Q2 transistor and single 2N3055 transistor are very much overloaded when the current is 3A and the output voltage is set low or is shorted.
The voltage from the transformer is too low for an output of 30V at 3A and the value of the main filter capacitor C1 is much too low which causes ripple in the output at high current and high voltage. 
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I have built a 5A version of this power supply. It seems it's working in some way but there is one 'load' problem. When I connect the 12V/60W lamp to PS and set both potentiometers to max. values I get around 11V at the output. This is somewhat strange so I think in theory this PS should burn out that kind of lamp. The problem is why is the voltage drop that big.

There is also another strange thing. I was measuring voltage levels in the circuit. Most values seem ok, except some values around  U2. When both potentiometers are set to min. there is few milivolts on the pin 2 and 3 but at the output pin (6) there is 10V. I don't know from where this voltage come from if the input pins are almost at zero value. In the other hand, when I set potentiometers to the max. the I measure around 3.5V at the pin 2 and 11.2V at the pin 3. At max. settings with no load connected I get 39V at pin 6.

I am using 30V/7A toroidal transformer and 3x2N3055 as output transistors.

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I have built a 5A version of this power supply. It seems it's working in some way but there is one 'load' problem. When I connect the 12V/60W lamp to PS and set both potentiometers to max. values I get around 11V at the output.

60W/12V= 5A. So the current regulator reduces the output voltage so that the current is 5.0A. The warning LED should turn on to warn you that the current regulator is reducing the voltage.

There is also another strange thing. I was measuring voltage levels in the circuit. Most values seem ok, except some values around  U2. When both potentiometers are set to min. there is few milivolts on the pin 2 and 3 but at the output pin (6) there is 10V. I don't know from where this voltage come from if the input pins are almost at zero value.

Maybe opamp U2 is damaged from having its supply voltage too high for it.

In the other hand, when I set potentiometers to the max then I measure around 3.5V at the pin 2 and 11.2V at the pin 3.

The opamp is clipping with its output voltage as high as it can go. It is not regulating. Something is dragging down the output voltage so that the negative feedback to pin 2 has a voltage too low. U2 and the output transistors are supposed to have a voltage gain of 3.074 times and the output voltage will try to be 34.4V. The output of U2 will try to be 37V or more. Maybe the pins on the transistors are connected backwards.
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Thank you for reply.

LED doesn't light at this current but it is working with lower currents just fine. It is true that the lamp is using 5A but I still think there is some power left even if transformer is overloaded. I think this is the reason why LED doesn't light.

However I changed the OPAMPs a few times (i have spare ones) but the problem is still there. Pins on transistors are connected the right direction.

I'll keep searching for problem...

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