When asked to estimate the coil current of a small Omron G5V-2 DPDT relay, most guessed around ... Even the tiny Omron G5V-1 SPDT relay shown in the examples below has a coil current of 30mA at 5V.

Using custom PCBs hosting banks of DPDT relays, he progresses from the basic AND and XOR gates to half adders and full adders, explaining how carry in and carry out works. Everything is modular ...