Humble 555 Gets a Boost for ESR Meter [Hackaday]

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[Peter Demchenko] wanted to use a low power TS555 in an ESR meter design. The problem is, he needed to handle significant current sink requirements for cases where the capacitor under test had a low ESR. The TS555 wasn’t up to the task.

However, [Peter] made an interesting observation. the output pin of the device can sink or source current. However, the discharge pin is exactly the same output but can only sink current.

But what if you tied them together? Using some equalizing resistors, that’s exactly what he did, and this roughly doubles the rated current sink capability. According to [Peter], you do make the circuit more sensitive to power supply variations, but that could be an acceptable trade, depending on your application.

The meter schematic confused us for a moment because the R3 and R4 designations are corrupted. Both the equalizing resistors, it appears, are 110 ohms. The schematic legend should read “R3 110” not “3 110.” The same for R4 which appears as “4 110.”

We do love unusual ways to use a 555. If you need to read ESR, and you have one of those ubiquitous component testers handy, they will give you a reading of ESR, among other things.