Arduino triggering a recordable greeting card audio module

Projects Discussion and Showcase Device Hacking
1

Hey folks, I got a few recordable greeting card modules like these: http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&item=221063227103&nma=true&rt=nc&si=OBchbxdESDmSuRd%252BBbh2CAt3ego%253D&orig_cvip=true&rt=nc#ht_2686wt_1397

I'd like to trigger them to play their recorded clips using an Arduino sketch. I know that one needs to be careful about how much current passes through a microprocessor pin, but I don't know how to tell if that will be a problem in this case. Ideally I want to do something super-simple like:

  1. Share vIn (5v) with the module, eliminating the need for its batteries
  2. Connect the 2 leads from the "play" switch to two pins on the Arduino. Set one high and one low to mimic the "off" state of the switch.

Then setting both pins low for a hundred ms or so should complete the circuit in place of the current momentary-contact play switch and make the module play its sound.

What should I watch out for here? If I do need to provide some isolation, what would be the simplest way to do it? Thanks.

2
  1. Connect the 2 leads from the "play" switch to two pins on the Arduino. Set one high and one low to mimic the "off" state of the switch.

You should only have to connect one pin to one side of the switch. Measure the voltage on both sides of the switch when the switch is open. Press the switch and measure again. The side that changes is the one connected to the chip. Use the Arduino output to the open-switch value (HIGH or LOW) and change it to the closed-switch value (LOW or HIGH) to emulate a button press.

The other side of the switch is likely connected to Ground or Vcc(+5V). In either case connecting an Arduino output to it is likely to cause a short circuit (LOW to Vcc or HIGH to Ground).

3

Ah yes of course. The switch is either passing or blocking current from one side to the other, and then switching to the opposite for a moment, and that's all I need to do. Thank you.