40 November 2014
BUILD IT YOURSELF
Most electronic devices today have a single button you push to turn them on and off.
Think of your cell phone, laptop, and even your TV. There is no toggle to flip, no knob to
turn back and forth, nor slide switch to move. So, how do you get one of these power
buttons into your project so your latest gadget can sit next to your other devices without
the embarrassment of a toggle or slide switch?
Microprocessors drive most of our devices, and many of these processors have the
ability to go into a low power sleep mode. In this state, the processor can still respond
to an external signal such as a button press. When you combine that with some circuitry
to control power to peripheral devices such as displays, radios, and servos, you have a
system that can turn itself on and off without much additional hardware. The December
2013 issue of Nuts & Volts described an add-on solid-state power switch from Pololu
which performs a similar function. As a regular customer of Pololu, I have been aware of
this module for a while. However, I wanted a cheaper, more flexible, and integrated
solution that wouldn't require me to stock another part. If you're using a microprocessor
and you're in control of the hardware and software design of your system, you can get
this power control capability at little to no extra cost in money or board space.
Use a Pushbutton to Turn
Your Devices On and Off