Cool Joule – 0uA ? Brainteaser

Full spec, details and solution below.

A variant of the Cool Joule circuit by TinManPower.
See his channel for the original circuit and ongoing experiments.
See Lidmotor’s channel for the circuit diagram and his own replication.

Cool Joule variant spec:
1.2V AAA 200mAh Ni-Cd battery
2x1000uH axial inductors
100uF electrolytic cap (circuit starts easier)
S9014C transistor
100ohm resistor
1N4148 output diode
Superbright white LED

Flashing oscillator spec:
Lidmotor ‘Penny’, see his channel for circuit diagram.
100K input to Positive connection.

So, how does it do it ?
On looking at the circuit, I realised that the Cool Joule was in fact switched off.
However, some components were still being used of the Cool Joule, for the flashing oscillator circuit.
The 100ohm Base resistor from the transistor, goes to the 1000uH inductor and then to the Negative rail of the battery supply !
Aha, so we now actually do have a connections path, without the Cool Joule full circuit needing to be in operation.
The use of the 100K input resistor to the flashing oscillator, plus those other components in the path, allowed the circuit to use less than 1uA and still run nicely.

Hope you caught it !
If not, the above is how it runs 🙂

You may also like...