VictorPS

Hi,

I have a small transformer, it will generate high voltage, using voltage doubler (Diode + cap), the voltage is about 1.5~2KV DC. the circuit is similar to neg ion generator, where voltage is high but current is very small.
The application is to test insulated of magnet wire, high voltage is applied to the wire and conductive brush, if insulated of wire is bad, it will sparking.

Now I need to detect if the HV is short or sparking , how to convert the spark or short to logic, so I can interface it to PIC MCU?

Thank you,

JimB

I suggest that you put a resistor in series with the HV supply and measure the current.
When there is no spark, there will be no current and no volts across the resistor.
When there is a spark, current will flow and there will be some volt drop across the resistor.
If you put the resistor in the earthy end of your high voltage circuit, interfacing to the PIC should be easy.

JimB

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jpanhalt

Assuming there is not some constant corona discharge, when it sparts, you should see a voltage pulse or drop. Rather than dealing with the HV side, how about looking across the transformer primary for a current surge with each spark as the circuit recharges? For example, I can monitor a capacitor discharge ignition by looking at the supply line currents. Also, assuming you have some sort of transistor oscillator driving the transformer, I have found with CDI ignitions that you can detect the spark by looking at voltages on the collector or base of the transistor oscillator. John

VictorPS

Yes, I will give this a try, it shall work too.

My idea is to connect a 103 cap---> resistor --->3.6V /5.1V Zener diodes --> Gnd.
When there is High voltage, I see a logic high, when spark, I may be see a logic 0. However, I have not try yet.

VictorPS

Thanks John, this possible too, may be I need an adc in MCU to detect the small change, as the transformer use is a small one...

Advantage is I can detect short circuit, so can give alarm or shutdown the HV for a while.

ronsimpson

Victor,
I think you are on the right path. Here is a typical way used in CRT monitors to monitor high voltage current. With low current the 1K resistor pulls the sense point to 3.3 volts (or 5 volts). Current causes the sense point to drop. –0.7 is the low point. Choose the resistor for the correct current.
ron

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ericgibbs

hi Victor,
I suspect you will not see a logical '0' across a zener, you may need say, a 10k resistor in parallel with the 5V1Z zener.

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"Good enough is Perfect"

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