Digital timer clock teardown

Here is a tear-down of a mains powered (230V 50 Hz) timer switch. Let’s look how this is built.

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Many mains power timers use mechanism that has mains powered syncronous motor, but this is different. This one has a electronic clock timer in it. There seems to be one clock IC with a crystal (around 4.19 MHz). The clock IC drives the stepper motor mechanism that moves the mechanical clock that controls the mains switch contacts.

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The clock is powered from mains power using transformer-less power supply. That power supply consists of a capacitor, power resistor and bridge rectifier. The output from bridge rectifier goes to a resistor, which charges the rechargeable battery, main capacitor and the clock chip. I could not see any zener diodes in this circuit, and I suspect that the rechargeable battery is used here also as the component that regulates circuit voltage (NiCad battery might act the same as a Zener diode). The battery has leaked which could be a reason why this does not work properly.

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The clock electronics is based on Eurosil 1115A that is an 8-pin clock chip which drives a stepper motor. It is equivalent to Intersil’s ICM1115A that has datasheet at https://www.datasheetcatalog.com/datasheets_pdf/I/C/M/1/ICM1115.shtml

Page 132 of the following document lists several Eurosil TIMEPIECE-WATCH/CLOCK ICs as cross references for Samsung parts: http://bitsavers.informatik.uni-stuttgart.de/components/samsung/1988_Samsung_Semiconductor_Product_Guide.pdf

Sources:
https://www.eevblog.com/forum/repair/recognize-this-ic/
https://www.badcaps.net/forum/showthread.php?t=8772&page=2

1 Comment

  1. drift boss says:

    I appreciate you sharing this important information with us

    Reply

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