RS232 Wiretap

If you need to monitor a RS232 line (or something else running through a D-Sub connector), use one of these open-style connectors. Their pins fit into a female D-Sub connector and provide ample space to attach probes.

PCB Etching Thermostat

A small thermostat I built for a sodium persulfate PCB etching bath, controlling a heater originally intended for fish tanks (with the original temperature control removed). The temperature is fixed to 45–50 °C and power is provided for a small air pump. Schematics can be found here, PCB design files and MCU firmware here.

Thermocouple via Integrated Differential Amplifier

Recently, I needed a simple temperature switch which could withstand 400 °C. A thermocouple can easily manage this but its generated voltage is unpleasantly small. However, it turns out that a ATTiny216A’s integrated differential amplifier is absolutely sufficient for a, albeit not very accurate, measurement. Enough to determine if something is hot or not, at least.

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Milliohm Meter Test Fuchs MOM1

While restoring a milliohm meter made by Test Fuchs I could not find any information about, I traced its schematic. It can be found here in case anyone has the same instrument.

IGBT Chopper

A useful thing to have for testing high voltage transformers is a simple chopper. This one switches a 600 V IGBT with an adjustable frequency between 50 Hz and 29 kHz (lower frequencies are possible with an external timing capacitor) and any duty cycle between 0 and 100%.

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