MAINS LED

[sargan]

I have a need to display ON condition of 19 mains signals (heating system)
Zone valves, Boiler, pump etc.

I can get the 220V 'ON' for each part easily enough .... want a simple way to have an LED indicate state ... illuminated = ON

Did a bit of Googling a round and many people use ccts and just drop power across a resistor ... eg http://www.youtube.com/watch?v=iXMjzlS1Jf8
not practical as heat dissipation of 19 of these is too much.

Found a more detailed cct .. here where capacitor almost removes any power drop across resistor.


Details & explanations are here http://www.marcspages.co.uk/tech/6103.htm

However one location seems to be saying you can drop the resistor all together and just use capacitor to limit current ...

Discussed here - http://www.instructables.com/id/LED-on-AC-Mains/


I'd be interested in simplest way to implement, without the heat dissipation issue. Could the last option be slightly modified without going for full wave rectification ?

[pebe]

Yes, you can use a cap without the resistor. Make sure that you use a capacitor with AT LEAST a 400VAC rating. Probably one of the poly types in a molded plastic box.

The diode can be a 1N4001 or anything else in the 1N400* range, because the only difference between any of them is the max reverse voltage rating - which in this case will only rise to about 3V

[sargan]

In the cct given there an advantage to adding the resistor on the other lead ?

[sargan]

When you mention Poly above - did you mean Polypropylene? (could be you meant Polyester)

[pebe]

To answer your previous question, I can see no advantage in adding the resistor.

By 'poly' I meant polycarbonate, polypropylene, polyester or any of the plastic dielectrics provided it will happily work at 230VAC.

[sargan]

Thanks .. I think the 220R was in effect to act as a fuse in the event the capacitor went short .. prevent excess current though LED

[pebe]

I think if the cap went S/C then the resistor would not protect the LED when connected to 220V. The resistor and LED would probably explode.

Much safer to fuse the common lead to the LEDs with a 1A fuse. There is a good chance that your heating control panel is already fitted with a small fuse.

[sargan]

I think if the cap went S/C then the resistor would not protect the LED when connected to 220V. The resistor and LED would probably explode.

Much safer to fuse the common lead to the LEDs with a 1A fuse. There is a good chance that your heating control panel is already fitted with a small fuse.

Thanks ... I can easily fuse the common Neutral at a low level, while the overall mains has a 3A fuse

Thanks