Arduino High Voltage Detector

Posted on Feb 6, 2014

Nothing really new: a JFET is used to sense the electric field generated by high voltage electric line; the JFET amplifies the signal very little, but it lowers the impedence and provide current to a level suitable for transistor amplification. The two transistor can be any low power NPN scavenged from anywhere. The two-transistor are configured a

Arduino High Voltage Detector
Click here to download the full size of the above Circuit.

s a sort of thresholded amplifier: when the voltage at R2 rises at above 3V circa, Q1 starts pumping current into the LED with a step curve providing a better go-no/go rensponse. The circuit is the same as the one used in the Korg Monotron to drive the LFO LED. A low current LED could have been connected directly between V+ and the Drain of the JFET and removing TR1, TR2 and R3 through R7: in this case the LED would light up in a linear way, no threshold. See bottom of post for a description of what TR2 is there for. Stray charge may escape from the tip of R1 for tip-effect letting the intrinsic capacitance at the gate of the JFET charge positively giving a positive read after a little while. So, a curled tip and a very high resistance path to ground in the form of a few turns of thin wire around resistor R1, help keep things in balance. In case, a very very high resistor can be connected between gate and ground (R8), but this will limit sensitivity very much. Resistor R1 is there to provide a protection to the delicate gate of the JFET and the delicate heart of the operator in case of contact to a live line. Here, the higher the value of the resistor, the better. R1 also provides for the sensing tip.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Simple digital thermometer with AVR
    Simple sine-wave generator has no low- or high-pass filters
    op amp ringer circuit old telephone
    low voltage cutout for 12v sla
    Two-LED Voltage Indicator
    Metal detector 2
    Barricade warning lights flashing circuit
    Photoelectric control circuit lullaby