Remote Start using Cell Phone: Part 2
It works! Not to spoil the punchline, but yeah, all the tests so far have worked out.
I received my breadboard from SparkFun and started assemblage. I used one of the two optoisolators I found in an old board I scavenged from- something. The optoisolator seems to be a good fit, at least for testing. The input voltage (datasheet) for the IL203 is 1.2v – 1.5v, which nails my averaging output of 1.35v perfectly. However, I do have some concern about the long-term operation of the optoisolator, as that voltage is rated at 20 mA and I measured the phone output peaking at just over 420 mA! That kind of continued current may damage the optoisolator in the long term, but as far as I know that datasheet could be telling me how long to cook eggs, so you tell me?
Anyway, here is what I got hooked up and working:
With that setup, I was able to kick off the vibrate on the phone by going to the menu and selecting the volume and get a nice tone out of my multimeter. Further tests by calling my phone and setting the alarm revealed that all of the vibrate functions on the phone resulted in nice *fairly* steady, long pulses out of the vibrate circuit. I took the setup outside and hooked the collector and emitter side of the transistor up to the part of the remote start that I wanted grounded. Adjusting the volume twice (to make it ‘vibrate’ twice) resulted in the accessories kicking on and my car starting right up. I was even able to repeat the process and shut my car back down! (YES! *pumps fist*)
Here is a closer look at the whole setup so far:
Now the next part of the project was the part I was holding my breath on… Making the phone not shut down the remote start with consecutive pulses. Again, a TON of thanks has to go to beegbie over at the12volt.com for his suggestion for this part of the circuit. Brother, it works like a CHARM!
The idea was that certain parts of the remote start circuit are only active once the startup sequence is activated. I chose to use the accessory circuit as it would remain on and keep the remote start from sensing any more inputs the entire time the car was running. (I am not worried, at this time, about being able to shut the car down since the remote start only runs for approx 15 minutes then shuts down on its own.) I achieved this by splicing into the collector side of the circuit on the optoisolator (the vibrate output) and installing a relay. This is your typical Bosch style automotive relay, and the idea was to have it triggered by the Accessory output on the remote start to open the circuit. Besides the fact that I bought the wrong kind of relay (I bought a NO relay and I needed a NC relay, see how I modded it to be a NC in my other entry) and had to modify it, it worked PERFECTLY (YES! *pumps fist again*)
Here is a pic of the clusterfuck setup I had for that:
With this all in place, a call to my car started it, and letting the phone continue to ring did not shut it off. I killed the car at this point, and set an alarm on the phone for 5 minutes. 5 minutes later, VROOM! Final test, I set an event on the calendar. Later that morning, I was presented with the beautiful sounds of my broken exhaust springing to life! I’d call that a success, wouldn’t you.
The next step in this whole shebang is to put the whole package into, well, a nicer package. I have ordered a board, matching project box, jumper wires and automotive relays from Parts-Express, and some low-current relays from Digi-Key. These low current, solid-state relays should be able to handle the higher mA current better than the opto-isolators, and might even last longer. I will say that the operating temperature of the optoisolators is better than that of the relays, which is of concern being jammed in a car in KY, where the weather can be anywhere from 0°F to 105°F. This I don’t get (the operating temps, not the weather…well, I don’t get that either, but…) as the general operation of the opto and the solid state relay are basically the same, except the opto has a transistor on it’s output side? (This I don’t really get either?)
So to conclude Part 2 of this mod, I am eagerly awaiting my orders from Digi-Key and Parts-Express (the coolest places have hyphens in their names). Hopefully soon I will have Part 3 up and have a nice little packaged unit. In the mean time, look for my post on how I modded a relay because I am too lazy to go drive around town hunting for the correct one.