Voltage on line detection

[Jimbo]

I have a small board about 4 inches by 4 inches with a plasma bulb on
it. The bulb is putting out a ton of RF, EMI, RFI, etc.... I want to
test to see if voltage is going to the bulb. How can I safely test the
line and tell my microprossor without giving it too much noise? Will
just a diode with a voltage divider work? What about if I put a BJT on
it? space is an issue though.

 

[Ken Smith]

I have a small board about 4 inches by 4 inches with a plasma bulb on
it. The bulb is putting out a ton of RF, EMI, RFI, etc.... I want to
test to see if voltage is going to the bulb. How can I safely test the
line and tell my microprossor without giving it too much noise? Will
just a diode with a voltage divider work? What about if I put a BJT on
it? space is an issue though.

You may only need the voltage divider.

You can make the resistor values very high so that the capacitance and
protection diodes on the microprocessor's input will keep the voltage
within the limits. The micro can sample the input at some highish rate
and assume, lets say, that if the voltage is there in any millisecond out
of 100 it is turned on.

 

[Jimbo]

are you talking about a protection diode that I add or is there one
built into pics that I didn't know about. I currently have a diode but
basically it's just to turn rectify an AC line.