Dark/Light Activated Relay
None of the parts are critical and easy available. The potmeter adjust the trigger 'on' level. The diode in the
diagram shows to be 1N914. This is ok if you have a light-duty relay, also the 1N914 is a signal diode so actually
does not qualify. Use a 1N4001 (or better) instead. A couple of substitutes for the 2N2222 transistor are: NTE123A,
ECG123A, PN100, etc.
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