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

#### Garrettmarvel

Joined Dec 28, 2014
6
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

#### tcmtech

Joined Nov 4, 2013
2,867
You could just buy an off the shelf programable timer and use that.

#### elec_mech

Joined Nov 12, 2008
1,500
two reasons i prefer the digital alarm clock hack is the LCD appearance for an end user, the cost is cheap at approx. $10, and they are dual alarm clicks with 2 scheduled alarm settings which is key for the product. see short promo video for product reference and purpose. If you program your own microcontroller you can have as many scheduled settings as you wish. If you prefer an LCD, would something like this work? There are several color options from other suppliers as well. You can get grey text on a blue background or blue text on a black background to name a couple. You can have it provide clear instructions to the user when programming and even add a countdown to the next feeding time as well as the current time. In the long run, you'll probably work with an LCD manufacturer to make a custom display, but this would give you a proof of concept. Thread Starter #### Garrettmarvel Joined Dec 28, 2014 6 If you program your own microcontroller you can have as many scheduled settings as you wish. If you prefer an LCD, would something like this work? There are several color options from other suppliers as well. You can get grey text on a blue background or blue text on a black background to name a couple. You can have it provide clear instructions to the user when programming and even add a countdown to the next feeding time as well as the current time. In the long run, you'll probably work with an LCD manufacturer to make a custom display, but this would give you a proof of concept. it might work, but at size and cost of$25 plus other required components it becomes more cost prohibitive than anything else when compared to $10 for the off the shelf clock, i think.... #### ScottWang Joined Aug 23, 2012 7,048 Mic → Amplifier → RC High frequency filter and isolation → Schmitt Waveform converter → Diode Cap rectifier → filp flop → Bjt → Relay. If you like then you can using logical level Vgs mosfet to replace the bjt and no needs to use relay. #### elec_mech Joined Nov 12, 2008 1,500 it might work, but at size and cost of$25 plus other required components it becomes more cost prohibitive than anything else when compared to $10 for the off the shelf clock, i think.... We can find less expensive LCD's, I just linked to one I knew off the top of my head - assuming so, is the size okay for your prototype? How many prototypes are you shooting for? Alternately, we could use a microcontroller to interface with an alarm clock to handle all the items I mentioned earlier. About$10 for a programmer and $4 for the microcontroller itself and maybe a$1-3 for additional parts (resistors, PCB, transistor, etc.).

Scott's solution is certainly an option too. You'll have to ask him about assembly if you want to give that a shot.

#### Brownout

Joined Jan 10, 2012
2,390
I like Brownout's suggestion, but the same problem is still present, although it use a piezo buzzer, so you could put a transistor between the output and your motor and it may be enough to drive the motor (via PWM).
Damn, you're right. In that case, I'd add a transistor and filter to convert and rectify the voltage. Or else, cut and jump the trace to a digital output and make a simple edit to the source code.
Look at page 60 here: http://www.atmel.com/images/atmel-2486-8-bit-avr-microcontroller-atmega8_l_datasheet.pdf The pins connected to the buzzer can be reconfigured to simple digital outputs, so no hacking of the board would be necessary. This is just one kit I looked at. You might find a cheaper one doing more research.

If you use a kit like this one, we could help making the program hack to reconfigure the pin.