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Isnt der a solution for my problem..

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Newbie level 6
Dec 12, 2012
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mine is a simple circuit with pic12f508 in it. it is getting affected wen i switch on/off other appliances in my home,i tried all possible ways.but its not working out.below is the schematic.pls find wer i hav gone wrong.. circ.jpg

in my opinion the problem is around the power supply : 1n4007 and 7805 and capacitors
not a good thing to feed 24v into a 7805 even for small current it's not made for it
try to remove the second 12v part of the transformer to fed only 12v into the 7805 it should be better
also increase the 2200uF capacitor, and put a small 100nf ceramic in parallel with it to remove high frequencies coming from the mains

Your BC558+ SW + 26K config is very unusual. What are you trying to do here ? I suspect this needs to be improved - especially when the Switch is open & your base floats.

Also imho your MCLR should be pulled to Vcc, even though it already has a (weak) internal pullup
An open pin can pick up noise easily and cause problems.

Also in general you should use a series resistance on the input of the 78L05. You are dropping ~12volts (1.414 x 12 - 5) across the regulator chip. This is fine, but can cause a bit of heating on higher loads. Even a load of 100ma would cause a 1.2w on the 7805. The 2200uF is an overkill - around 100uF - 220uF will work fine, but do put a 0.1uF or 0.22uF ceramic in parallel also.
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thank u all.the mistake was in using bc558, now i used bc547 with some bias resistors and the problem is totally solved. and i offcourse changed the logic of the program..
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