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I would be supprised if you got the full 8amp max peak current and continous 5amps with .22R unles you have used more fo them.generator***** said:I built this power supply. for current resistors I used four 0.22Ohm- 11Watt. ıt works great thanks wizpic for PCB
KoZu said:I have a nice 200VA 12V toroid transformer that I would like to use but unlike the transformer used here, it has a single secondary winding. Is there an easy way to use that instead? Or could someone maybe tell me how to modify the given schematic to use with my transformer?
Also, how do you display the current limit?
Q80 said:Hi wizpic,
with your PCB there's a lettel problem the Fluctuations of the current !!! the current display is not stable ?
Q80 said:The problem with your PCB there’s no connection between the groundplane and the earth, but you can fix this problem with the shunt between the pin of current resistor and the body of your PSU.
I did the PCB & the meter just like the original one ; a 100% like the original one ; and its works like a magic
The current sense resistor is a 0.1R resistor and when you draw a current it produces a small volatge acrross it in Milli-volts, This can be between 23-400MV depending on how much current is been drawn(this is only an example). The PIC'S A/D converter cannot really really this and struggles to cope with such low volatge. The way I did it was to use an op-amp set up has again amplifier so the voltage then would be come say 0-5V. If I remember when I carrying out some testing without the current LED connected the PSU played up. I may be wrong but it has been some years since I built it. What you can do is leave the LED in place and use a pin on the PIC then when it goes high show it up on the LCD but I think the LED just does the job fine.KoZu said:I'm also thinking of using a PIC to display the voltage and current with transistor temp and fan speed on an alphanumeric lcd display. What I don't really understand is why on the original schematic is the current measured between the negative output and ground? Can someone explain to me in detail, how and why can I measure the current using the PIC's ADC? Also.. is there a way to show the current limit or is the LED the only way to know that the limit has been reached?~K