Simple status lamp for 120 VAC circuit using LEDs 1

[Doorman352]

I have a DC load bank that I use often, it is operated via a microcomputer control card that is prone to failure.

I am trying to design a simple board to replace the microcomputer with 12 toggle switches to control 12 120VAC solenoids, which is what the microcomputer board is supposed to do when/if it works. The board is for backup, while the controller is being repaired or stuborn.

In my haste to simplify the problem and solution, I was reminded by a coworker that a "Pretty" status light would be necessary since people can't look at the position of a toggle switch and determine it's state...... I left that alone....

I need a simple solution to add a status indicator, the voltage is 120VAC, and I'm limited to 24-28 AWG wiring, so I don't want to alter the circuitry too much. A small device with little power consumption that turns on when the toggle is closed and turns off when open.

This should have been easy...... I read the post about the 120 VAC LED and power supply, but I need to limit the voltage drop to the solenoid and I don't want a huge power consumption to create heat problems.

Can an LED with a blocking diode and a resister in parallel achieve this? Is there a better way?

Thanks

Doorman352

 

[MikeHalloran]

A neon lamp and resistor can.

http://members.misty.com/don/nitelite.html

If you want to spend a little, you can buy rocker and push/push switches with neon indicators built in.




Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

There are scads and scads of LED indicator available. Probably many thousands.

Go to any of the electrical supply places.

Or on line:

http://www.alliedelec.com

http://www.mouser.com

http://www.newark.com

http://www.ledtronics.com

I would look for switches that have built-in indicators. A light comes on in the switch when the switch is turned on. Find one that fits your present switch cutout and just replace the existing ones - no further fabrication.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[benta]

The classic way to drive LEDs from the mains is with a series capacitor.
Don't forget:
1: a rectifier/diode in antiparallel to the LED to provide a path for the negative "wave".
2: a series resistor to limit inrush current when switching on.
3: a resistor in parallel to the capacitor to discharge it when switching off.

Best Regards,

Benta.

 

[Skogsgurra]

Sometimes it is better to let one's mind leave the "box". Find out why the microcomputer board fails instead.

Could be such a simple thing as transients from the solenoids that upsets the board or kills one of the drivers.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[richs]

Hiya-

Benta suggestion might also include.

4. Do not use a polarized capasitor.......

 

[peebee]

Transformer-type LED's are the best for these applications. The transformers are designed to clip any voltage spikes which would otherwise damage the LED's. Listed in all the industrial controls catalogs from Allen-Bradley, GE, ABB, Siemens, etc.