Indicator Light 12v

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I have a 12v bulb 12w with a switch with only a positive wire and no = chance of getting a negative wire to pick-up. It is an architrave = switch so not a lot of room. Is there any way I can get an indicator = light/LED to work.

Is there some way of dropping the voltage slightly with diode and = getting an LED or something to light.

Many thanks in anticipation.

Reply to
Mike Manuka
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chance of getting a negative wire to pick-up. It is an architrave switch so not a lot of room. Is there any way I can get an indicator light/LED to work.

an LED or something to light.

I think that it's on a 12VDC supply. If so, a smaller resistor, about 560 ohms, would be better.

... Steve

Reply to
Steve

So I take it the LED would be ON the whole time the switch is off?

If that is that case, 10mA an hour over 24 hours is nothing compared to leaving the light on all night which happens. Plenty of solar power to take care of the 240mA over 24 hours compared to minimum 8A if left on all night.

Many thanks and appreciated.

Reply to
Mike Manuka

On Fri, 19 Sep 2008 22:31:23 GMT, "Mike Manuka" put finger to keyboard and composed:

getting a negative wire to pick-up. It is an architrave switch so not a lot of room. Is there any way I can get an indicator light/LED to work.

LED or something to light.

If you are looking for a way to illuminate your switch in the dark, then connect an LED and 10K series resistor across the switch contacts.

- Franc Zabkar

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Reply to
Franc Zabkar

On Sat, 20 Sep 2008 13:53:35 +1000, "Steve" put finger to keyboard and composed:

Yes, that was a typo. I was aiming for 10mA from 12V, so I should have specified 1K.

- Franc Zabkar

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Reply to
Franc Zabkar

On Sat, 20 Sep 2008 09:00:58 GMT, "Mike Manuka" put finger to keyboard and composed:

Yes. I'm assuming your light is an incandescent type that provides a low resistance path to the negative terminal.

You could experiment with higher resistances and high brightness LEDs. You could also try a flashing LED which would require less current to be effective, although the flashing may be annoying.

Here are a few Dick Smith LEDs:

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BTW, that's 240mAh and 8Ah.

- Franc Zabkar

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Reply to
Franc Zabkar

Franc are you saying the LED would take 240mAh and 8Ah? If it will, is there something else that would use substantially less? Can you get itsy bitsy teeny weeny LED's that use low power?

Yes, it is a standard filament bulb.

I don't imagine I would be to popular with her ladyship if I used a flashing LED.

Many thanks and also for the links.

Reply to
Mike Manuka

240 mAh to operate a LED at 10mA for 24h ,

presumably 8Ah is the cost of leaving a 3W lamp running for 24h ??? not sure.

absolutely, leds will light with only the tiniest aount of current flowing through them (they only light the tiniest bit however, but if the goal is locating the switch in the pitch black that should not be a problem)

best results are had with leds marketed as high-efficiency.

1mA is sufficient to make an ordinary led (jaycar CAT. NO. ZD1694) bright enough for it to be visible in dark daytime shade, and to stand out in the dark.

with about 0.2mA I get a glow comparable to those glow-in-the-dark bedlamp switches. With a high efficiency led you could go to even lower power usage.

Bye. Jasen

Reply to
Jasen Betts

On Mon, 22 Sep 2008 08:24:09 GMT, "Mike Manuka" put finger to keyboard and composed:

Ampere-Hour is a measure of charge. If you draw 1A for 8 hours from a battery, then the battery will have lost 8Ah of charge.

In addition to what Jasen has said, you could use several LEDs in series across the switch. Some high brightness LEDs have a significantly higher voltage drop than ordinary LEDs, so some experimentation may be in order. You might get away with 4 or 5 bright LEDs and a resistor that sets the current at 1mA. Just bunch the LEDs together, like an LED night light. That will give you 4 or 5 times as much light output for the same current.

- Franc Zabkar

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Reply to
Franc Zabkar

Many thanks. Bought a 3mm orange LED from Jaycar, 1k resistor and uses

11mA. I may try the next resistor size up and see how bright that is and if it reduces the power v LED brightness.

Many thanks for the assistance. Sincerely appreciated.

Reply to
Mike Manuka

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