Saturday, 21 January 2017

HOME AUTOMATION: WeMo Maker as electric door latch relay

I recently tested the WeMo Maker to replace the electric door strike relay I had installed that was controlled via my doorbell. I picked it up for $69 from Bunnings Warehouse.
The idea was that I would replace the wireless relay that came with my doorbell for the Wemo Maker and then use the WeMo app (possibly with IFTTT) to unlock the door from my phone. I didn't plan to use the sensor input feature on the device. 




Setup was easy, I followed the instructions that came with the device and was up and running in about 15 minutes. It was soon after setup that I realised the limitations of the device...


The issues:

In order to work as an electric door strike relay I required the device to function as a momentary switch, turning on for a short amount of time and then turning back off to lock the door again. Typically devices built for door unlocking operations have a latching delay that can be set by a jumper, meaning that when the door is remotely unlocked it will be held unlocked for the set amount of time. So with the WeMo Maker I needed it to do the same.
When I took a look at the settings of the device I noticed there was no setting for the 'on time' of the relay. Some googling led me to discover that the WeMo Maker is only capable of a 300ms on time as set by the firmware, making the device pretty much useless for my remote entry needs without some extra circuitry.

IFTTT to the rescue:

WeMo have made their products compatible with the IFTTT platform making it possible to connect hundreds of services to the device.
After sifting through all the services trying to find one that allowed me to connect a countdown timer to the device, I found that one of the default WeMo Maker IFTTT actions was "on then off after 2 seconds". Perfect!

The results:

In reality the way this setup had me using the device was not ideal, be default the device didn't allow me to set a relay 'on time'. While I was able to get around this with IFTTT the reality of the service was that I was getting an approximately 8 second delay from pressing the button widget on my phone to having the door lock open. Combine this with the relatively short amount of time that the lock was open and the result was me having to just repeatedly pull on the door waiting for it to unlock after pressing the unlock button. Not ideal given the cost of the device. 

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