Is it possible to modify a digital alarm clock as a timer power switch?

[garrettmarvel]

i have an automatic pet feeder prototype that i’m trying to develop where I’d like to use an off the shelf digital alarm clock to act as the timer to start the power flow to a DC motor?

in my ME mind, the chip that is given the instruction to make alarm speaker beep should be able to somehow be modified to initiate power to the motor.

is this possible? or does a custom board or chip have to be designed?

my hope was to hand modify a few digital alarm clocks and integrate them into the prototype to save money on EE custom design costs for a small run of prototype builds, since a simple alarm clock function and LCD screen, buttons, etc. is what i need to just turn on the motor when the scheduled alarm time occurs.

any thoughts?

thanks!

garrett

 

[Greg Togtema]

I see a way to make it possible with a bit of adapting, but my answer is still theoretical:

Some basic digital alarm clocks use a "divide by 60" counter to convert the 60Hz wall signal (in Canada/US) to a 1Hz signal to count seconds. It's a crude design since the frequency may be 57Hz or 63Hz, but oddly it averages to 60Hz pretty well. So if you open up a digital clock, you may find these counter ICs. If the clock is primitive and uses Dual Inline Package ICs (through-hole chips with about 7 pins on top and 7 on bottom), you can look up the IC number and find if they are counter ICs. Now if you are so lucky to find this to be true, then you need to know the condition on all the bits that correspond to the desired alarm time. Feed all those pins into an AND gate, which drives the digital signal of a motor driver (digital signal cannot drive the motor directly).

After writing this and rereading your reply, try taking a look on ebay or AliExpress. Some people create custom circuits for $5-$10 that are timers and have the display integrated into it. It is probably easier to use timers than clocks, but good luck at any rate.

 

[BradtheRad]

See if you can locate the wire that turns on a radio, or beeper, etc. You should be able to take your 'ON' signal directly from that.

You'll use that signal to turn on a relay (or transistor, mosfet), and that will drive your motor.