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I'm trying to build a mobile device testing rig to hold 10 tablets.

The tablets should be constantly charging via USB cables plugged into a power strip, but when I publish new content to the devices (via a specialized wifi app) I want to walk over to the rig, flip a switch and begin a continuous power cycle (off/on every 10 seconds) that will wake the devices and keep them awake while I'm standing there. When finished I want to flip the switch off to end the power cycle and continue normal power to the devices.

I've seen short-cycle timers like this (http://www.amazon.com/Digital-734170-Short-Cycle-Timer/dp/B00AKEOQWE/ref=sr_1_1?s=hi&ie=UTF8&qid=1439664239&sr=1-1&keywords=short+cycle+timer) that could potentially do the trick, but it's not quite there.

Any suggestions appreciated!

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    \$\begingroup\$ Other than a relay and a sub-hertz oscillator? \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 15 '15 at 19:15
  • \$\begingroup\$ A 555 Timer even \$\endgroup\$ – Passerby Aug 15 '15 at 19:16
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A 555 timer could do the job, but a small microcontroller with a stable time base, zero crossing detector, and internal timers would allow for more accuracy and a lower cost AC relay (vs. solid state relay) to be used.

A small AC coupled power supply is used to generated the 5V needed. The microcontroller will also monitor the AC supply with a "zero crossing detector" to know when to close the main AC relay (closing at 0V prevents arcing, allowing a lower cost relay to be used).

Microchips 8 pin device PIC12F1501 comes to mind.

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  • \$\begingroup\$ I would venture to guess that accuracy is not one of the requirements for this. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 15 '15 at 22:51
  • \$\begingroup\$ @Ignac: Probably true, but what's your point? Do you want him to increase complexity to get worse than the few percent error you get with a PIC 10F or 12F? \$\endgroup\$ – Olin Lathrop Aug 16 '15 at 1:05
  • \$\begingroup\$ Thanks for the comments, folks. Is there anything "pre-built" that would get me at least most of the way there? I'm not an experienced electrician and although I can probably hack my way through some basic stuff I'm not sure I can program a microcontroller correctly. The accuracy of the timer is not super important to me, it just needs to power cycle between 1-20 seconds to counter the native sleep mode of the device. Thanks again for your suggestions! \$\endgroup\$ – Jordan Chamberlain Aug 16 '15 at 18:12
  • \$\begingroup\$ @Tom Walter: I'm looking at something like this: greners.com/i/meters-timers/timers/timers-complex/… that's aaaaalmost there. I just need the time settings to be more fine-tuned (seconds vs. hours). Any suggestions? \$\endgroup\$ – Jordan Chamberlain Aug 17 '15 at 17:07

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