Darkroom circuit one time exposure

Posted on Dec 11, 2010

Darkroom circuit one time exposure It audible signal when the developing time is coming. This circuit can be used to put photofinishing big timer, it can also be used for many

Darkroom circuit one time exposure
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other occasions. The FET VTi, resistors, capacitors and other components at a given time segment, by the transistor VTz, transformer T and the speaker sound signal segment is B and so on. When the potentiometer resistance RP adjusted to zero, the timer delay of 1 ~ 1.5 min; RP when resistance is adjusted to the maximum, the timer delay is 10 ~ 15min. Tone audio signal depends on the capacity of the capacitor Cz, and the delay time depends on the capacitance Cl capacity. Closing the switch s, the exposure start (exposure lamp circuit, not shown), the audible signal at the end of the horn. And this time should be cut off the power supply to avoid wasting energy.

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