Remote Start using Cell Phone: Part 1
Recently I added a remote start to my car. All is good in the world. Unfortunately, I work at an airport and my car is about a 15 minute shuttle ride from my office. There is not much opportunity to ‘stand at the door and wait for warm car’ there.
But cruising the web, I happened upon the Viper website, where I read about a new system where you can start your car via an iPhone from virtually anywhere. After looking into the system, I soon stumbled onto the fact that the system is ridiculously expensive, as is everything that has to do with the Goddamned iPhone newer technology. Further research on the subject yielded little hope, as all other systems were out of my budget (cheap as hell).
My co-worker and I started daydreaming on the subject (what goes on at an airport that we would need to pay attention?) When I stumbled on an idea. My remote start has a wire called the Remote Start Activation Input. Now the job of the RSAI is, from the manual: “This wire will start the vehicle when it sees two negative pulses. Only used when incorporating into existing alarm or FOR TESTING PURPOSES.” That last part I capped and bolded, as that is what is most important for me. “Testing” consists of simply grounding that wire for two pulses in order to start the car. Two more pulses shuts it down, exactly like using the remote.
Bingo, I had my way in! Here is what I came up with:
I hope you can tell what is going on there. If not, here is a synopsis, and a little bit of method behind my madness…
The remote start requires 2 pulses within 3? seconds to initiate the remote start sequence. So how to send those 2 pulses? Easy, I remove the vibrate motor from a cell phone or pager and use that circuit to initiate the remote start by setting the phone to vibrate. But wait…the RSAI only works when put to ground, that circuit has (after testing) a 1.35v current. I guess I have to use a relay! Oh no…The remote start turns off after 2 MORE pulses. How do I get the cell phone to STOP sending rings? Hrm…
The answer came from beegbie over at the12volt.com. The remote start start up sequence goes like this. Sense Input>Turn on Accessories>Try to Crank Engine. If I put a normally closed relay on the vibrate circuit triggered by the vehicle accessory circuit, then once the remote start sequence kicks off, any subsequent rings by the phone won’t be ‘heard’ by the remote start.
Here are some pictures of the tear down and modification of the cell phone:
Purchased this phone for $10 from CVS Pharmacy along with $20 worth of prepaid minutes. Phone came with a battery and wall wart charger.
Removed the 6 tri-wing (fail) screws holding the inner bezel on. Once off, all the goodies are revealed. You can remove the PCB fairly easily, but for the most part it is single sided.
Here I have already removed the vibrate motor and soldered wired back into it’s place. I wanted an easy way to remove the phone if I needed to make any modifications to it or add minutes, or hell, even make an emergency phone call. I decided on desoldering the headphone jack from and isolating it with that paper stuff I got from another board. I glued the paper down, then glued the jack to it. Then I soldered the pins that correlate to the 2nd & 3rd pins on the headphone jack to the wires coming off the vibrate motor resistors. I chose (had no choice) to solder the wires to the resistors due to me tearing out the traces on the pcb when removing the motor. I was a little skittish applying the amount of heat required to remove that bish, thinking I might desolder some of the tiny little components around it. Also of interest to some would be my choice of wire. That is two strands from a IDE connector. One is marked to denote it’s polarity. (It helped, really.)
Here is a picture of the headphone jack lookin’ all normal and stuff. I like a nice clean install. This way the phone loses only the functionality of vibrate and using a headset. I can still set the ringer, make calls, etc.
Here is the modified headphone jack for the hookup. This is a 2.5mm (mini) headphone jack that I had from a cheap headset from another phone. The wires were those damned coated wires, and quite puny at that, so I cut apart the boot and desoldered them at the source. I then removed 2 wires from a 10ft piece of cat5e and soldered them in place, shrink wrapped and Bob’s yer uncle. Why, you should ask, did I use Ethernet cable. Several reasons: It is sturdy, it was solid not stranded, I could pick my length and I have about 300 feet in a box behind me.
All in all I think the thing may actually work. I need to source some cheap solid state relays that initiate below 1.5 volts. I am also thinking about maybe using an optoisolator, as I have 2 in a scavenged pcb beside me that are in the correct voltage range. I will still need a 30A auto fuse for the other relay, though. I have a breadboard on order from Sparkfun that should come in handy for testing.
The best part of this project are the possibilities. Not only can I remote start my car from afar, I can also use the other features of the phone to automate the remote start. I can set up to 4 alarms on this phone, and set them to vibrate. Since I work 4×10 shift, that is perfect for starting my car everyday before work. Also, that phone has a timer on it that can also trigger the vibrate function. Haven’t figgered out a practical use for that yet. But the Pièce de résistance is the Calendar. I can set nearly unlimited events into the calendar, and set an alarm to trigger the vibrate at or before the event in 15 minute intervals. I can also set the as ‘recurring events’, too. I could program in mine and my wife’s work schedules, upcoming doctors appointments, ANYTHING! Not bad for a $10 phone. I am glad that I decided to make the phone easily connect/disconnectable.
Check out Part 2 to see if I can actually pull it off.