Posts posted by tdx
20v transformer it is. Now just a few quick questions before I order parts because of some parts list and schematic conflicts:
1) Schematic shows a 100nf poly cap (labeled C10 on some schematics) between the negative line and the emitter of transistor Q3 & opamp U3's Vcc, but is not on parts list, should this be removed completely?
2) Resistor R15 (100 ohm) is nowhere to be found on schematics, delete?
3) The 10v 1w Zener is missing from my parts list, but this should be added right? There should be a 5.6v and 10v Zener?
Thanks again for your guidance.
Starting to make more sense now. Now if the intended load will be typically run at 4-12 volts 50% duty cycle (electromagnetic machine), never exceeding 18v then would it make sense to further step the transformer down to 18v 4a? The load shouldn't exceed 1 amp, 2 at the most. Would 18v with at least 10,000 uf C1 keep the remainder of the circuit functioning properly?
Am I correct in thinking that if this power supply is turned on even with no load, or a very light load the power transistors will actually be hotter than running at higher output voltages correct? Say if it were at 5 volts of output they would have to burn off more than if they were cranked up to get rid of the difference between their input from the transformer and the output load correct?
I haven't seen a 1/2W resistor for about 45 years. If yours are that old then they probably have their values changed.
Hmm... the parts list calls for a 1/2W resistor on D3 (220 ohm). I'm looking at all new parts from Newark, it's just that some values for resistors have a better selection in 500mW or are actually cheaper than 250mW.
Also I noticed the schematic and parts list don't quite agree on the Zener and LED, the parts list calls D12 the Zener and LED1 as the LED, but on the schematic D12 appears to be the LED and the Zener is unmarked? I assume its just the labeling and the schematic placement is correct?
Thank you for the feedback audioguru. I am using what appears to be the latest revision you have made with the MC34071/TLE2141 opamps with the parts list using red text to indicate the part changes, I've attached them below to verify they are the correct revision. So if I use a 24v 3.3A transformer and set the voltage pot to my 20v max needs I would not need to make any further changes as far as parts go correct? But could I feasibly reduce the C1 capacitor to less than 12,000uf? Also I'm pretty sure its safe, but using 1/2 watt resistors in place of 1/4 watt would be fine in this circuit as in most, correct?
Thanks for your help
Hello everyone. I am looking at building this power supply for a specific use which requires 0-20 volts and typically up to 2 amps, so my question is can I save some money and take some weight off by stepping down the transformer just a bit? Would a 24v 3.3 amp such as the Hammond 185E24 work if I never need to exceed 20 volts?
0-30 Vdc Stabilized Power Supply
in Projects Q/A
I have built this power supply some time ago and used the PCB in the PDF attached for it. From the PCB's posted it is by far the best I found with proper trace sizes and probably the best layout you can do for a single sided board with this circuit. The PDF includes a redrawn schematic and parts list but the part names DO NOT MATCH the ones posted by audioguru and others, so pay close attention when assembling.
The attached PDF is not mine, I forget the username of the person who created it but all credit goes to them.