493
Item nr.


Selecttime 1728638 Clock switch

Efficient switch.


Data for Selecttime 1728638
Production, 2009.
Cabinet.
Power230V, 1W (or 0.1W with capacitive ballast).

The Design

Q: What, can you repair everything?
A: No, only things that are broken.

In 2019, my ten year old clock switch refused to switch any more. I bought a new switch, an electronic one from AliExpress, and after arrival decided to open up the Selecttime. The new switch came with instructions front and back. Inside the Selecttime I found a tiny synchronous motor, mechanically driving a clock reel and switch. The switch lever laid loose in the clock but wasn't broken, and I could easily reinstall it, and the clock switch worked again! So I had two operating clock switches and could compare them.


Obtained12/2009 from Action store.
Condition8.
Value (est.)2,2€.

This Object

What would you expect to run more efficiently, a mechanical or an electrical switch? I use a timer to switch off my lights during the day to save energy, but how much energy does the switching cost?

While repairing the Selecttimer, I plugged it into my power meter and found a draw of 1.0W, not very much, but still over two euros per year (at electricity price of 23ct), meaning the clock ate 20 euro's during its decade of infancy. The digital timer (left) is very nice, it contains a battery and retains time and programs for half a year. I measured its power consumption to be 0.6W, a bit cheaper than the mechanical clock.

But wait, what is that black thing in the Selecttimer (photo above). It's a 47k ballast resistor, feeding the motor with just 5mA so the motor sees a low voltage. That 1.0W I measured goes almost completely in this ballast! What would happen if I replace this resistor by a 30nF capacitor (shunted by a 470k bleeder)? Well, nothing, except the power consumption suddenly drops to about 0.1W! Another little succes in the War on Vampire Consumption. The motor has a resistance of about 4 kiloOhm, so the capacitor is still adequately protected against power spikes. My ballast cap of 30n is a bit low, actually. To get the same original current of 5mA, a cap of 50 to 60 nF would be a better fit. But appearently, the motor works on a much lower current, too. In November 2020, I replaced the ballast by a more suitable 47nF capacitor, but when I measured it two years later, it was only 30nF still. I placed an X2 capacitor of 47nF on November 21, 2022. Unfortunately, the clock stopped running on July 27, 2023, because of lost capacity of that part.


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