i cant see the resistor i only see the terminal of the buttons and i measure the voltage across one button when it not pressed and it was 160V.What is the value of the resistor in each push button and what is the number of push buttons ? (More than 15 could be 1000 !)
This sounds like a number of buttons next to doors in a building that switches on lighting in corridors.
what is the type of the resistorIf we assume that the resistor in each button is 220K (Which I think is a reasonable figure.) then 30 of them in parallel is 220k/30 = 7.3K The peak voltage of 220 V RMS is 220 x 1.414 = 311 volts If we assume the voltage across the neons in the push buttons is 60 volts then would have 251 volts (peak) minus the maximum voltage we can allow across the common neon without it striking, If we assume this is 50 volts then we have 201 volts across the resistors in parallel. 201/7300 = 28 mA (Peak) so we need a load resistor of 50/0.028 = 1.8K. When one of the buttons is pressed there will be 220 volts RMS across this resistor so it will dissipate 220^2/1800 = 27 watts. I think using a relay or small transformer would be a better way to provide isolation than the neon/LDR method.
the value of capacitor depends on the number of buttons ? using capacitor suitable for all method ?I agree that you would need a load of some sort unless the relay was a large contactor that required quite a large current to pull it in. Using a transformer you could probably use a higher value load resistor (Which would make the neons in the push buttons dimmer.) but you could rectify the secondary and have an adjustable threashold detector. If you used a capacitor as a load you would need about 2 uF (It would need to be X or Y rated for this sort of application.
The capacitors must be at least 250 volts AC rating and X or Y class (This specifies how they behave when they fail.) Contact supressors such as this one could be used. As these are 0.47 uF you would need four of them in parallel to give a reactance of about 1.8 K. The fact that they have a built in series resistor is an advantage as it would reduce the large current pulce if the button is pressed near the crest of the waveform.
You could probably get away with using a 1 uF capacitor (Or a 3.6 K resistor which would reduce the power disipation to 13 watts when a button was pressed.) This would slightly reduce the brightness of the neons in the push buttons.
i need a neon lamp to be on when any of parallel buttons pressed .
i test circuit 1 it works as i need.
but if i used buttons with their indication lamps as in circuit 2 the neon lamp always on even any buttons not pressed.
View attachment 114008
could anyone explain the problem ?and how can i solve it ?