The FADU F-Stop Enlarger Timer is an enlarger timer which can optionally drive a WiFi smart switch or relay module to switch the enlarger's lamp on and off. It has f-stop timing adjustments for either single-exposures or test-strips, including a mode with audio cues designed for those who will be switching the enlarger lamp manually.

Of note for version 1.5 is the ability to use Sonoff Basic R3 and Mini devices in DIY mode without the need to reprogram their firmware. They should be boxed and suitable cable strain-relief and earth/ground continuity maintained as appropriate.

Free and open source, the source code is available on GitHub (https://github.com/filmanddarkroom/FADU_Timer). User instructions and details of the various Wi-Fi switching interfaces are also in the manual on GitHub.

The timer can be used as a stand-alone timer to calculate f-stop timing for manual on/off switching of the enlarger but can also be used to switch the enlarger lamp via a commonly available WiFi smart switch (Sonoff Basic, Mini, S20 or S26 etc). The Basic R3 and Mini may be used without reprogramming but the S20 and S26 will require changing their firmware. Alternately, an LC Technologies WiFi relay board module may be used without the need for reprogramming - but as it is a bare pcb module it will need a case and a 5V power supply. The LC Tech board does not require any reprogramming but should only be used on the low-voltage side of an enlarger power supply's transformer/stabilizer due to poor pcb layout decisions by the manufacturer making it, in my opinion, unsuitable for use with mains voltages.

Reprogramming the Sonoff Basic and Mini switches requires some electronics knowledge, but if you have experimented with the Arduino system it should not present any major difficulties.