I have a liftmaster opener with a garagemote installed. I discovered that the "lock" mechanism can be triggered by applying a 22mf capacitor across the 2 leads for about 1 second, and then turn it off in the same way. When the opener is in a locked state it fluctuates the voltage across the 2 leads, which makes the LED on the wall button blink. I was thinking about ways to add this to the garagemote, but I am not sure how. I don't know if I would need to use another relay to insert/remove the capacitor, or if a transistor would work? Also, I am unsure of the available pins on the moteino. It looks like D3 is unused, and maybe D8 since I don't have flash installed. I think I could use something similar to a battery voltage divider to detect if the voltage was stable to determine if it was locked or not, and I think A2 and A3 are available for this. Ultimately I'd like it to lock the door at night and unlock in the morning. Any help would be appreciated! Thanks.
So you're talking about the same 2 leads which garageMote is shorting (via the small relay) ?
In that case I think another relay (same) with the 22uF (you said mF but I doubt it has to be that large, you probably meant uF) capacitor configured to short the leads through the cap when its closed. Then you could use another 2 unused pins - D7 and D8 are usable if you have no FLASH A2 and A3 are usable on Moteino. Schematic is here (https://lowpowerlab.com/guide/garagemote/schematic/). You would wire the relay the same as the other, with the diode for protection, add your cap, mod your code for the lock feature, and .. experiment :)
yes 22uF, sorry I was overthinking micro farads and the symbol for it. Yes it does use the same 2 leads that are used to initiate an open or close motion, so the 2nd relay would do exactly what you said. I wasn't sure if a transistor would be enough to handle that, so I appreciate the input. I do have another one of the relays that is the same as what came with the garagemote kit so I will just use that. Thanks!
Essentially two GPIOs can turn ON the tiny relay (if you use the same).
Otherwise you will need a transistor, with a different beefier relay.
I have another question after studying all of this a bit more. D6 and D7 need to be used together to turn on the relay to open/close the door, but you said I could use D7 and D8 together to turn on the relay for the lock feature. Will it cause a problem if I am using D7 for both of these functions? Since it takes 2 to have enough power to energize the coil I am wondering if using D7 for both of these would be a problem, for example cause overcurrent on that GPIO because there is more load (2 relays in parallel). I know it would take the combination of either D6 or D8 in addition to D7 to turn on the appropriate relay, I am unsure of the overall effect of D7 being connected to both inputs. Also I see that A0 and A1 are used for the hall sensors, so I am not sure how I could use those for this purpose. Thanks for the help and suggestions!
Oops I was wrong, you should use 2 unused pins, both separate from other relay pins.
ok I got it working. I used D16 and D17 for the relay, and made a little add-on board with the relay, cap, and diode that connects to the backside of the garagemote. The only thing I didn't get on it is the voltage monitor to actually tell whether it is locked or not (the fluctuating voltage), but I figure if I control it using the garagemote then "in theory" it should be right... It's not a super critical thing, so I guess I am okay with it. After I thought about it some more I wasn't sure how I would be able to tell if the voltage was fluctuating with a voltage divider. The voltage pulses pretty fast so I am not sure if I'd see that on the moteino. If anyone has an idea on that I'd appreciate it. Anyway, I also got the GUI updated with a new button to lock/unlock it, and (bonus!) it even works with homebridge. Since i have an Apple TV that is a lot more convenient to use remotely than VPN or exposing the gateway to the internet. I have attached my code if anyone is interested. Thanks for the tips Felix!
Great!
Some photos to top it off? New UI button/mote screenshots?
OK here are some pics. Thanks again for the help.
another
interface
node ui
Nice work, thank you for sharing code and photos!