About the time the 1 Hz Challenge was announced, I was looking through my ancient electronic parts, in particular germanium transistors. I formed the idea to use one in a 1 Hz blinky that could be fitted into a round case. By getting a round tuit, I would then be able to finish all outstanding tasks. A super power!

I wrote a description of the Garner oscillator some time ago. I have modified the circuit slightly from that page.

The Falstad circuit has been uploaded as an attachment to this project if you wish to simulate it. The 1.8MΩ resistor and 470nF capacitor were chosen to give an approximate rate of 1 Hz, per the formula given in my page, to fulfil the challenge conditions. The value of the resistor can be trimmed but accuracy is not the top goal as this project goes into the Ridiculous category. Capacitor leakage may make the circuit fail to work, hence not electrolytic and 470nF, around the largest value normally encountered for TH components.

The Garner oscillator has a very short duty cycle, all the better for long battery life. I have powered it with a pair of 1.5 V alkaline cells that have already done years of duty elsewhere.

The PNP germanium transistor is a CV7001, described in my exploration account. One difference you'll notice is a base resistor to ensure that collector-base leakage doesn't turn the transistor on. The complementary NPN transistor in the pair is silicon so I chose one of the oldest specimens in my collection, a BC109 from the late 60s or early 70s.

A white LED is very efficient at the low current, and the phosphor afterglow "stretches" the blink. The 100Ω resistor is to limit the current rush when the capacitor charges. If you are wondering about the 4.7kΩ resistor in parallel with the LED and current limiting resistor, it's to ensure that the collector is pulled up to the negative rail. (Remember that ground is the positive rail for this PNP-centric transistor circuit.)

Here's the circuit, transferred to a piece of veroboard.

I even have a round tin to hand to enclose the circuit as a round tuit, exposing the LED through a hole. But the pressing question is: Should I do it? If I do then I will have got a round tuit, which means I will have to finish all the tasks on my list, and not just the electronic project ones. That will leave me no time to enjoy life!