120 volt LED design

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1500 leds in parallel.

Bob

Have you heard of current transformers? That is what I would use to connect a pair of LEDS in series with an AC load.

Perhaps something like this one: ttp://

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Regards,

John Popelish

I don't think you understand what the OP is asking for.

To me, it seems like he wants something that will light up when when a light load is connected to his "led box", and will also light and not blow up when a 15A load is connected to it, too.

This is not such a trivial design.

Bob

h72$bab$ snipped-for-privacy@aioe.org...

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U can use a capacitor as a resistor for ac ccts. Cheaper than xfmr as long as u keep it safe.

Johns current transformer idea sounds like a good one a little amplification with an op amp and you have lots of range. or a hall sensor. current probe etc.

Bob

h72$bab$ snipped-for-privacy@aioe.org...

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thanks for the response, I do believe I will have to incorporate a CT (current transducer) I know that LEDs can't handle current and will now need advise on hooking up a very small CT to light up an LED when current is detected, on a 120 volt AC line. thanks for all responses. (And yes I do have a brain,)

A cheap way to sense current is to wrap a few turns of one wire around a read relay. mmm good for "bulb out" sensor on a car but not sure about Ac? Then use capacative reactance for Led supply. Mike

You replied to a forged post by jackthehammer. I have never had an account with aioe.org.

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Michael A. Terrell
Central Florida

No, that's not realistically possible unless you want to spend hundreds of dollars minimum and light up the room.

A small metal core toroidal current transformer (run a wire through the core for the primary) can be used.

Best regards, Spehro Pefhany

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120V~ | | | | | | | | +-----+ | o | | | | | | | +-----+ | .-. | | |5V~ 120V~ | | |2k2 | .-. +---. ,------+ .-----. | | | | | | )|( +-| ~/ |-+ '-' | | |.02R/5W )|( +---| / = |---+ | | '-' +---' '----+ '-----' | | | | | 100mA | V LED | +-----+ | - | | | | | o +---+ | | | | | | created by Andy´s ASCII-Circuit v1.24.140803 Beta

For measuring or signaling current the best thing you can use is a current transformer. But this tend to be expensive things that are not always available.

If you only want to signal the current in 10-15A range, the circuit above will do. Be sure to make proper connections between the 0.02R/5W resistor and the main line. A bad connection will become hot and fry itself. The resistor will become hot as well so provide enough ventilation. Connect the transformer directly to the resistor (so not to the line). The transformer can be a ordinary 100mA type. Even a 50mA type may do though it can become a little bit too warm. Mention its orientation. Use a low current type for the LED. A 2mA type will do.

As the circuit is directly connected to the mains, use proper insulation.

120V~ does not always kill but you don't want to be the exception... I guess :)

petrus bitbyter

I would put two big diodes in reverse parallel, and that goes in series with the load. Then use a transformer to step up the voltage across the diodes to a level that will light an LED. This will have the LED brightness only varying a little with load current, as long as the load current is enough to make the transformer light an LED.

- Don Klipstein ( snipped-for-privacy@misty.com)

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Problem is, you might get a current spike that blows the LED when the thing is switched on or off. I tried to use an LED in a 1KW space heater as an indicator light, and just used a diode and resistor across the low voltage fan which was in series with the heating element. It worked for a few hours and then blew the LED. So I replaced it and tried again with same result. I finally just put the LED and large power resistor in parallel with the entire load and never had any more problems. The extra heat from the power resistor just helped heat up the room.

-Bill

OK, I would either add a bridge rectifier or use two inverse-parallel LEDs. A suitable dropping resistor is needed of course.

With the transformer primary's voltage limited to a diode drop, I doubt anything bad will happen to the LEDs unless those primary diodes fail open or the power line is hit by lightning. (Put a fuse in series with the transformer primary in case those diodes open.)

- Don Klipstein ( snipped-for-privacy@misty.com)

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Yes, it will probably work if the 15 amp power diodes are fast enough to respond to short current spikes. I think my problem was the inductance of the fan motor bumped up the voltage considerably when power was switched off.

-Bill

Just buy a 120v LED indicator and wire it in parallel with the load. Then load current from 0 to blows the breaker does not matter.