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My mains voltage is 230V AC/50Hz.
I need to turn on a LED when main voltage goes to 240V.
How to do that? What method should I use?
Look at:
**broken link removed**
You would first have to rectify and filter your incoming AC as the application circuit is designed for monitoring DC voltages.
Lefty
If a neon lamp fires at ~62v and wants less than 1mA passing through it, make a voltage divider across the 240v with an ~11k 4w and a ~4.3k 2w resistor and connect one end of the neon to the resistor junction and ground the other end.My mains voltage is 230V AC/50Hz.
I need to turn on a LED (neon?)when main voltage goes to 240V.
How to do that? What method should I use?
220vac gives about 60v across the neon, 240vac gives about 65v @ 1mA.
230/6V = 8.484 (smoothed DC)
= 4.242V---216 (8 bit read val)
240/6.26V = 8.852 (smoothed DC)
= 4.42V----225 (8 bit read val)
220/5.7V = 8.115 (smoothed DC)
= 4.05V----206 (8 bit read val)
You will need a load or else the response for voltage dropping from 240 to 220 will be to slow.
hi Suraj,
Can you buy LM393's [dual comparator] at your location.?
Yes eric gibbs I can buy.Also it must use with PIC12F675.
Understood.
You say that you are short on PIC pins.?
Use an external LM393 as a comparator to compare the mains low voltage against a reference voltage.
The output of the comp would be low for less than 240V [this could drive a Green LED] and high for 240V or greater [drive Red LED].
Or use the PIC to drive the LED's.
Just poll the comp output.
LM393 are not expensive.
Hello eric gibbs that will be fine but I don't know how to calculate the comparator references & AC inputs to the comparator against 230V AC.
hi,
If you decide to use that method, we will help with the sums.
You could use the on PIC comparator if required.