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Power on LED.

Started by flester, September 12, 2018, 03:53:15 PM

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flester

I added a 'power on' LED to my TDA2003 amp and it is really draining the battery. Not sure if attached schematic is clear but it is between input ground and the + supply pin on the board. It's a green LED rather than the usual green with 2k resistor and 9v battery.

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flester

Sorry I meant I normally use red LEDs

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phatt

The drawing is not clear but it could be in series with supply neg which would just drop voltage to the circuit.
Phil.

flester

I think you are right. Is there a better way? I hope this drawing is clearer.

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phatt

Yes that will work,,, just don't forget the series resistor otherwise you will fry the LED 8|
Phil.

flester

Actually that is how I have it wired (with series resistor). Maybe I have a short somewhere?

BTW is there a good app for drawing schematics? I used Paint for this and it took a while

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g1

What kind of battery are you using?
Measure the voltage across the series resistor and calculate the current through the LED.  What is it?

flester

Sorry not had a chance to measure it. Its a 9v pp3 battery

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flester

I suspect it may be something else draining the battery, even when switched off. Have taken out LED and going to fit new battery just to see.

BTW I am using cheap supermarket batteries but they usually last OK in other projects. I did measure a new one and it read 11v  when disconnected. Is that normal?

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66cccfff

Green LEDs, especially extra-bright ones, are no doubt battery eaters. Using a red one with a resistor with higher resistance (Just let the LED glow slightly) will work.