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Leorick writes - "Make your own lab power supply complete with adjustable voltage and constant current source." - Link.
Make a Lab Power Supply
Posted by Phillip Torrone |
Apr 17, 2006 03:59 PM
DIY Projects, Electronics |
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I'm not an expert at deciphering schematics. Where do you connect the outputs? What is the range of the variable voltage or current? How much power can it supply?
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The "Dummy Output" 500 ohm resistor is in parallel with the output. It provides a minimal load so the regulators are stable when there's no external load applied.
By chasing the schematic I get a voltage output range of 0 to 36.4 volts and 0 to about 0.8 amps for the current limiting. Good design - I'll rebuild an ancient Eico supply I have using it. Thanks!!!
Jim Horn, WB9SYN/6
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In the center of the schematic look for the "Dummy Output" resistor. This resistor represents your load, left side is positive, right side is negative. The 2n3055 is rated for 15 Amps! It would have to be very well heat sinked for that though, your bridge etc would also have to be beefy. I would guess that it is probably set up for a 3 or 4 amp max load (that seems to be about the norm).
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LOL, must have been typing at the same time as Jim :)
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I don't suppose that anyone feels like giving some clues as to which pins on the LM324 go where on the diagram.
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I don't suppose that anyone feels like giving some clues as to which pins on the LM324 go where on the diagram.
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Look at the bottom of page one for the pin outs.
http://www.national.com/ds/LM/LM124.pdf
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I am stumped with the voltage divider at the ammeter. The component list asks for a 100uA ammeter at 1k ohm. This is in parallel with a 0.22ohm resistor. I can't see how this gives a useful reading on the ammeter.
Also, note that although the component list calls for a full wave bridge, it seems the stripboard actually builds one from discrete diodes.
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100uA meter is connected in parallel with the 0.22Oohm resistor, as it acutally is a voltage meter. If you think about the Ohms law, (U = R * I), you can see that when the current through the 0.22ohm resistor rises, the voltage over it rises too and the ammeter needle moves. This way it is really simple and cost-effective to measure currents. Scale of the meter has to be adjusted before use.
And forgive me for bringing this old post to life, but has anyone tried to make a PSU using this circuit with a smaller transformer? I have 24VAC and 17VAC transformers and I don't want to buy a new one, since those are big enough for me. Do I have to adjust components (zener voltage, resistors) in order to make it work?
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