bf2015
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Variable Power Supply 0-25V/0-2.5A With LCD and Button Control
bf2015 replied to bf2015's topic in Projects Q/A
Here are the power schem and the power control schem in pdf. powerdoubledsidedschem.pdf powercontrol.pdf -
Variable Power Supply 0-25V/0-2.5A With LCD and Button Control
bf2015 posted a topic in Projects Q/A
I'm just getting back into electronics after about 15 years, just getting into Eagle, and am looking to build a "fairly straightforward" power supply, and I came across this power supply on Felixls for a variable 0-25V/0-2.5A power supply with an LCD readout and button controls. The site is in Spanish, but I have translated it and have included the theory below. I been reading the 0-30V Stabilized Power thread here on Electronics Lab, but this power supply is really all I need. My questions are: 1. This power supply seem to be "fairly" straightforward. Is it a decent design (not underpowerd/won't overheat, ect)? 2. I have made the schematics and boards in Eagle (I've included the eagle zip and also the pdfs). Can somebody take a look at it and make sure I have done everything right? Are my routes wide enough? Where can I put ratsnests? The boards are doublesided, and since I will be doing the "make-your-own-board-with-toner" method, I was thinking about making 2 single-sided boards and then put them together to make the double-sided board. Any suggestions much appreciated. Site Link: http://translate.googleusercontent.com/translate_c?act=url&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=auto&tl=en&u=http://sergiols.blogspot.com/search/label/Digital-Power-Supply&usg=ALkJrhjkal1Ctp4N19PuSq4wsLhHFwWDgA Description This project is based on changes in Valdorros Osvaldo (see forum thread TodoPic ) to the power supply elektor magazine's number 260. The source has the following characteristics powereaglefiles.zip powerpdf.zip -
The problem I am having is that I have no current control. If P1 is at max and I turn P2 to max, then both the voltage and current drops to zero, and vice versa. The LED never lights up. And the max current never gets above 0.9A.
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The problem I am having is that the led current limiting led never turns on. When I increase the voltage pot and then adjust the current pot, the voltage drops as it should and the power transistors heat up, however, I never get an indication from the led. I've tested the led and its good. Suggestions? Bad U3 maybe? I'm using MC34071s on a dip8 socket. (Note: I had to cross-reference BC556 with NTE's part which is NTE159. I assume the EBC pins are the same for both)??
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So from the above mod that I posted, I connected everything up and after about 2-3 seconds c5 blew its top. What could be the cause? I thought that Q2 might be shorted to the heatsink, but it wasn't. I have voltages that I can post if needed.
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Audioguru, thank you so much for your quick reply and clarification. One other question, which might seem elementry and mean that I need to refresh my understanding a little more. On the above pcb that I posted, why are there 3 power inputs (+, alternating, -)? Is this because a full wave bridge recitfier was used on a center-tapped transformer prior to board connection?
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Hi. This is my first post on here. I have been reading through the entire thread on this revised PSU and it has been an enormous refresher for me. I am using tesseract's revised pcb 5.0A and have a few questions. First on the board layout, the power transistor terminal block is labelled B (pin 1) and C (pin 2) which I would assume means Base and Collector. But on his shaltplan schematic it shows pin 1 going to the collector and pin 2 going to the base. Which is correct? Also, RV3 limits the max current, so am I correct in assuming that if I use a power supply less than the specified 7A and set RV3 to my power supply's amperage rating that it will limit the max current to what I set it at? Sorry for the questions. It's been about 15 years since I built a board.