It's a while since I've partaken of wine while making a video, and it definitely adds "something" to the mix. Notably me screwing up the triac connections. No wonder I got tongue twisted during that bit.
MT1 goes to the neutral and MT2 goes to the fan. The gate should be shown on the neutral side too.

I got this fan purely to analyse the humidity monitoring circuitry. These units are built to a price, and that means that they have to use the cheapest humidity sensor possible, which introduces significant design complexities.

This bare HR2902L style humidity sensor uses a conductive membrane that changes resistance with ambient humidity levels. But you can't just measure it as a simple resistor. To avoid electrolytic effects and the risk of changing the characteristics of the sensing layer, it has to be read with AC current with an equal current flow of either polarity. The same technique is also used to avoid electrode corrosion with water purity analysers.

The timing function is much simpler. Just reading a voltage between zero and 5V and then converting that to a scaled value for a counter.

This fan was advertised as having an antibackdraught shutter. I was hoping for a waxmotor actuated louvre system, but in reality it's a very cheap and nasty floppy plastic flap that will work, but will potentially make flappy noises on a windy day.

The fan also has its own short video due to an oddity that occured while I was experimenting with taming its speed down with a series capacitor. I stepped the capacitor value up progressively and suddenly at 1uF the fan went into turbo mode, and the voltage across it exceeded the mains supply significantly. I reckon I hit a magic ratio between the motor inductance and capacitance that caused an unusual phase addition issue.


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