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Author Topic: Power on LED.  (Read 974 times)

flester

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Power on LED.
« on: September 12, 2018, 03:53:15 PM »

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

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Re: Power on LED.
« Reply #1 on: September 12, 2018, 03:54:21 PM »

Sorry I meant I normally use red LEDs

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phatt

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Re: Power on LED.
« Reply #2 on: September 12, 2018, 09:36:41 PM »

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

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Re: Power on LED.
« Reply #3 on: September 13, 2018, 09:53:25 AM »

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

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phatt

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Re: Power on LED.
« Reply #4 on: September 13, 2018, 10:39:21 PM »

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

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Re: Power on LED.
« Reply #5 on: September 14, 2018, 02:44:43 AM »

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

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Re: Power on LED.
« Reply #6 on: September 14, 2018, 12:30:10 PM »

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

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Re: Power on LED.
« Reply #7 on: September 18, 2018, 05:02:35 AM »

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

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flester

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Re: Power on LED.
« Reply #8 on: September 21, 2018, 05:55:40 AM »

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

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Re: Power on LED.
« Reply #9 on: October 14, 2018, 09:04:53 AM »

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.
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