Fry Another Day

Electrostatic discharge (ESD) events are not just for messing with your friends after rubbing your socks on the carpet on a dry winter day. As anyone that has ever designed a complex electronic circuit knows, ESD can cause all sorts of problems with their operation. And they are some of the worst kinds of problems — sporadic, mysterious, and extremely difficult to diagnose.

When you are not even certain what is causing your circuit to fail, it is almost impossible to fix it. A seemingly random glitch could have any number of causes, but if you can confirm that it is in fact the result of ESD, some specific design changes can help to eliminate the issue. So Clem Mayer has designed a DIY ESD detector that can identify nearby discharges. Not only that, but the detector outputs a signal that can be read by an oscilloscope or logic analyzer and be correlated with other signals to determine if the discharge is associated with your circuit’s bad behavior.

Mayer’s design borrows from an ESD detector circuit created by Charles Wenzel. An antenna serves as the input to this circuit, and when enough voltage is detected, it will trip a cascade of transistors. This ultimately outputs a five volt analog signal that can be fed into external devices. The signal is also fed into a Microchip ATtiny412 microcontroller, which gives more control over how the signal is represented digitally at its second output — it could be either five volts or zero volts, for example, to indicate that an ESD event has occurred.

While the electrical current of an ESD event is typically very low, it may measure in the thousands of volts. As such, the detector, with its microcontroller and other electronic components, has got a dangerous job. These components could easily be fried by high voltage levels at any time, so Mayer took an additional precaution. He installed the device’s custom circuit board in an EMI-shielded enclosure. This ensures that the high voltages remain in the portion of the circuit that was designed to deal with them, and do not spill over into more sensitive components that operate at low voltage levels.

Not only is this build a low-cost way to add an important piece of test equipment to your lab bench, but it also doubles as a lightning detector. Using the same outputs, the device could be used to, for instance, shut down a sensitive instrument to protect it from a potential power surge associated with a storm. If you are interested in building your own ESD detector, be sure to check out the project write-up and video for all the details that you will need.