DIY Electronics and Hardware

Over on YouTube [DENKI OTAKU] runs us through how a 4-pin MOSFET works and what the extra Kelvin source pin does.

A typical MOSFET might come in a 3-pin TO-247 package, but there are 4-pin variants which include an extra pin for the Kelvin source, also known as source sense. These 4-pin packages are known as TO-247-4. The fourth pin provides an additional source for gate current return which can in turn lessen the effect of parasitic inductance on the gate-source when switching current, particularly at high speed.

cross-posted from: https://programming.dev/post/38688621

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I'm a very impatient man. I want my tea at a drinkable temperature immediately.

It's a Panasonic BQ-390 AA charger, which used to be renowned as the best "smartest" AA charger.

The addon is an ESP32C3 with a 96x64 color OLED display, and an ADS1115 ADC.

The flashing dots indicate which cell is currently charging, as the charger only gives 0.5A to one cell at a time. The delay in voltage display is due to smoothing and filtering out stray voltage readings.

It can be powered either from the 5v regulator coming from the AA charger itself, or external USB power using a switch - the regulator in the charger isn't strong enough for the ESP32C3 to connect to wifi, so if I want to track charging status over wifi, I have to give it the extra USB power.

I got a lot of help from this ancient Japanese blog post I found of someone else who did a similar thing to the same charger:

http://act-ele.c.ooco.jp/jisaku/BQ390/bq390.htm

I am autistic and I fucking love sensors and data. I put all of them on one screen. It's like heroin for me.