Any suggestions.? I currently use a 4R7 in the ground line to turn on a BC547 and LED when the current >150 nominal and the resistor(1/4 W) gets quite hot... It's quite good because as the current drops, the LED dims and then goes out.....I now have a circuit that I need to indicate >450mA. So I'm thinking a 1R5 'pro' 1 watt... Trouble is , there's 6 of them in a small plastic box and if the resistor gets too hot, the plastic may start to deform.Current is limited to 600mA. Am I going to get e hex high side current switch for not a lot ( if at all?)
Low cost current indicator
Apr 18, 2008
2 Replies
You could replace the BC547 with an LM339 or LM324 and a lower sense voltage, or you could pre-bias the BC547 a few hundred millivolts with a resistive divider, or a schottky, or...
What does your circuit look like, do, run off of, etc. You haven't told us very much.
Huh?
Cheers, James Arthur
I have a recent project that does current sensing with a 0.15 ohm chip resistor made for current sensing. An op amp amplifies the voltage across the Rsense.
There can be a heat problem in some apps if Rsense needs say a 0.6V drop to provide base current to a transistor.
D from BC British Columbia Canada
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