How to Detect 220V-230V-240V ?

[Suraj143]

I have 3 LED’s. What I want is

When the AC 240V is there it must lights RED LED.
When the AC 230V is there it must lights GREEN LED.
When the AC 220V is there it must lights YELLOW LED.

Do you have a simple technique to do this? If I just add resistors when 240V case it will lights up all three LED’s. I need one LED to light up at each voltage.

Thanks

 

[gregmcc]

i'd use comparators with voltage dividers to detect when the input voltage is at a certain level

 

[stevez]

Something that might be of concern - the definition of 220 vac, 230 vac, 240 vac. Is 220 vac really 215.00 vac to 224.99 vac - and 230 vac really 225.50 vac to 234.99 vac ..and so on. Not trying to make this hard but it might matter depending on your application.

 

[Glyph]

is your AC a sine wave or a square wave? the peak voltage of sine wave 220V AC is higher than 220V so your method of detection might need to take this into account.

 

[Leftyretro]

I would consider using a small filement type transformer with say a 6 volt secondary winding. Your high voltge AC would drive the transformer primary. You could then rectify and and filter this low secondary voltage and then scale it in half with a resistor divider and then measure it with a PIC AD channel as 0 to 3 VDC value. The software could then measure and determine which LED to light up....

Lefty

 

[ronsimpson]

Do a search on the parts LM3914, LM3915, LM3916.
They are used to make LED meters often used for audio level. They are built to drive 10 LEDs but you can use only 3 outputs.

Make DC from your AC. (diode and cap) Then divide down to 5 volts.
Normally the LM391x is used like this.
LED1=.5 volts led2=1 led 3=1.5................led10=5
In the application there is a way to set the bottom led to non zero.
LED1=4.0, led2=4.1, led3=4.2......
In your case you could set the bottom led for <210 and the top led >250 with a total of 10 steps.

 

[CheapSlider]

zener

use zener diodes in series with the LEDs.

The AC voltage would need to be rectified and smoothed. The safest way would be to use a transformer to reduce the voltage

Assuming supply of 240V AC, secondary 9V
(transformer ratio = 230/9= 25.55555)

Supply secondary Smoothed DC
220 ___8.608 ____12.172
230 ___9.000 ____12.726
230 ___9.391 ____13.279

Each LED is connected in series with a zener diode as a tap off a potential divider. Each tap is adjusted so each LED lights up as the voltage is increased. Note as the voltage rises more LEDs will come on.

Though the circuit is fiddly to set up, it is cheap to make.

 

[Hero999]

Another question: why?

What are you actually trying to do?

Have you considered buying a panel meter?