Goes to show you that modern equipment does not always lend itself well to add Z-Wave home automation. Winter is approaching, so want to control my low-voltage mattress pad heater.
It requires the on/off button to be activated after power is provided.
Now I can waste $49 on a Remotec Z-Wave dry contact module, but I would still need the DSC06106-ZWUS to measure the power usage.
Not afraid to void warranties or apply some rusty skills it was time to see if I can mod the DSC06106-ZWUS and add a dry contact myself. Tried to communicate with Aeon-Labs first to get more technical information, but eventhough they did reply, it was nothing that would help me on this venture.
Examining the insides of the DSC06106-ZWUS in more detail I already discovered that the driving transistor is a 1AM SMD type, most likely manufactored by Diodes. Technical specs tell me that maximum current is 200mA for that one, and the BRT3-SS-105DM relay used for the main power only requires 80.6mA at 5 Volt usage.
That leaves plenty of current left to drive another small relay in parallel.
Now holding down the 'on/off' button on the mattress pad heater does turn it on and keeps it on, but the circuitry on it might be designed to expect more of a momentary pulse.
Now I must not be the first to attempt modding an existing Z-Wave module, and could use some help to avoid pitfalls.
My current DIY attempt would be to use the JQC-3F miniature relay that also uses 5Volt DC on the coil side, and supports 5A 240V AC or 30V DC on the relay side (more then sufficient for the low-power mattress pad heater circuit). Coil resistance = 70Ω (+/- 7Ω), Rated Coil Power = 0.36W (48VDC 0.51W), and dimensions are 19mm x 15.5mm x 20mm, which might even allow me to fit it inside the DSC06106-ZWUS case.
Then the tumbler switch output of that relay would drive another JQC-3F relay with a capacitor inbetween, as per:
(http://www.simprojects.nl/images/Image12.gif)
which will allow for a momentary pulse contact result to simulate a push button via Z-Wave.
However there are a ton of Adruino modules available that might also do this in a more elegant style, so I am open for suggestions. Perhaps there is a 5Volt miniature relay available with build in momentary support.
A bag of 10x JQC-3F would cost me $6.16 and 5x 470uF electrolytic capacitor are $5.03 via Amazon Prime, giving me enough parts to modify five Aeon-Labs modules. Only need to modify two for myself, but I am sure the spare parts will find a use for a future project.
One thing that worries me is that the JQC-3F is rated for 0.36W, which means at 5Volt it draws 72mA. That means the 1AM transistor would have to drive 152.6mA total. This is still well below the maximum specifications of 200mA, but perhaps somebody can make a suggestion that I am overlooking.
