Need help with remote vehicle start

I’m very new to the Spark board and I would like to set up the Spark Core/Photon to remote start my car. My plan would be to use the Core to virtually press the buttons in my key fob. From what I’m reading, it looks like I could use a solid state relay that the Core will control to close the switch (press the button).

Can someone recommend a relay to use? My fob (part# 92201609) runs on a 2032 button battery which outputs 3V.

How would I wire the relay to the Core? What terminals on the Core would I use to wire to the two sides of the button?

My car requires the lock button to be pressed and released, and then the start button to be pressed and held for about 2 seconds. Could I program the Core to “hold” the start button?

I would really appreciate any help or links anyone can provide.

Thank you,

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Can you post a picture of the top and bottom of the fob’s circuit board? You may not need to use SSRs at all if the thing is 3.3v tolerant

Thanks for your reply.

I was wondering about being able to use that similar voltage to my advantage. It should be able to work with the 3.3V just fine. I’ve read where some people have used two type 2016 3V batteries in place of the single type 2032 3V battery to up the voltage to 6V to get more range with their fob (using the same fob part number as mine).

Would I be able to wire the Core directly to the fob? I’m able to simply jump the switch with a short length of wire, so basically, that’s all I’d need the Core to do. The lock button is in the center of the fob, and the start button is in the upper left in this picture. I’d have to do some tiny soldering to connect to the two sides of the switches.

Would there be any trouble using the Tinker app to program the Core to “press” the lock button, then “press” and hold the start button?

Thanks for your help,

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Cool! Thanks for the pics. It’s great to hear that the FOB is fairly voltage tolerant.

I think the ultimate goal would be to wire the SparkCore directly to the FOB, power supply and all, and use it to “push the buttons” as your said

How about a few more questions/requests:

  1. How much does the FOB cost? Do you recognize that, while the chances are small given the voltage tolerance, you could kill your FOB and might have to replace it?
  2. Would you mind annotating your top / bottom pics? It’s be nice to see an arrow to each button explaining which it is and an arrow to which connections need to be bridged to unlock or remote start the car
  3. Do you have a multimeter/voltmeter?
  4. With the board pressed into the battery part of the FOB can you find + and - for the battery? I’m trying to find a voltage reference for 3. and it’s hard to really see what’s connected to what

@cody I know that on most current vehicles that have a keyless start, if you need to purchase an additional FOB you not only have to purchase the hardware, but the dealer will have to add the new FOB to the vehicle programming. This can run you up to hundreds of $. Just be careful not to destroy your current FOB.

Also you may want to look into a 12v - 5v USB power supply (one that plugs into your 12v car adapter. The core will draw 200 - 300ma when transmitting - so you will wear out a battery very quickly. If your FOB can handle 3.3v then you could power it from the core.

@cody, do you plan on placing this setup in your car or in your garage? What’s the plan?

Thanks for your response!

  1. I’ve found replacement fobs (which includes the board and black plastic casing with buttons in it) for $22. I got two with my car, but I’d buy a new one to use for this project.

  2. I’ll try to get an annotated picture uploaded a little later.

  3. I do have a multimeter.

  4. The side of the battery that we see (and what connects to the four tabs in the center of the board) is the - side of the battery. The opposite side (and the outer rim) that connects to the tab on the outside of the white circle is marked as +3V on the battery. I’ll try to get an annotated picture of all of this, but I also have a hard time following the connections as they go around the board.

Thanks for the heads up. I did do some researching into fob programming, and for my car (a Pontiac G8) the replacement fob programming instructions are actually in the owners manual (I was surprised and excited to see it should be simple to do).

I do plan on leaving this in the car (along with a wifi hotspot I already have) so I am planning on using a 12V car power adapter to power the Core.

I was a little worried that if I used one fob to start the car, and then tried to use a different fob to unlock the car, that the car would freak out and not let me in and go into theft deterrent mode. But I did some testing and the car didn’t mind me using two different fobs at all.

your a lucky man!

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Here’s some annotation on the front side of the fob board. I don’t know what SW4 is on the board. The “Panic” button is on the back side and is labeled SW6.

Ok. The next steps (for me at least) would be to do the following:

Let me know how that goes

Doesn’t matter which button and don’t have the power connected when you do this

I measured resistivity between contacts 1 & 2 and it read from under 4 ohms (which is the same it read when I touched the multimeter leads directly to each other, so it was effectively 0 ohms). I got the same measurements between 3 & 4. There was resistance off the meter when measuring from 1/2 to 3/4. When I press the button the resistance from 1/2 to 3/4 drops to under 4 ohms.

As I mentioned in my second post, I can use a jumper from 1/2 to 3/4 to “press” the button. So that’s what I would need the Core to do.

Also, when I measure from the left side of SW2 Lock (left in the picture, so 1/2) to the negative battery connection (the four armed thing in the center of the circle on the back side) I get under 4 ohms.

Awesome! Sorry for repeating things, just wanted to make sure we were on the same page

Ok, Next steps, if you connect a wire between 3/4 and - bat does it act like the switch has been pressed? What if you measure between 3/4 and -bat?

If the button does “act” like it’s been pressed then go ahead and solder a jumper to +bat (on the board, remove the battery completely) and plug it into a breadboard and then do the same with -bat. Plug the jumper from +bat to 3.3v on the core and -bat to GND on the core. Power up the core (again, no battery) and see if the FOB works. If so, solder a jumper to 3/4 and plug it into D0. Before powering up the core this time write a short script which makes D0 and output and write it “HIGH”. Then, in the loop have it go LOW for 250 or so milliseconds before returning high for 1000 milliseconds or so. That should “push” the button every 1.25 seconds.

This will be cool

Usually a design like that has a common circuit between all the buttons. Without the battery, just look for continuity between one side of all the buttons, then see if that’s connected to + or - of the battery. So if it’s common ground, all you need is ground connected anywhere and anther to your button (or any others you want to control). The pin you connect to can be set to input, then to simulate the button press, set to output and low for the pulse period, then input again. If they’re all connected to positive, then it’s just output/high with the same connections.

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When I jumper from the -battery to the 3/4 position, it does activate the button. I did not take a resistivity measurement there though.

Is a breadboard needed? Couldn’t I just wire directly from the -battery connection to the GND on the core, and from the +battery connection to the 3.3v on the Core?

Unfortunately, I don’t have my Core yet, so I’ll have to hold the project here for a week or so before I can get it connected and start programming it.

The breadboard was just a suggestion because I’m not a fan of soldering things to my Core. I would suggestion, for prototyping, that you go the breadboard route. The core comes with one!

Now that you know you just need to GND 3/4 you can easily get the Core to do this. Setup something on Guthub perhaps? and I’d love to lend a hand / watch your progress

Just one thought if you plan on using the cigarette lighter socket to power this - in many cars when the ignition starts, the car cuts power to the socket (I’m not an electrical engineer, but this is presumably to protect connected devices from a brownout followed by an induced surge as the alternator kicks in).

So make sure you test the Core/keyfob combo being plugged in and remaining responsive through a few cycles of starting your car - It may not make a difference once the computer has got the signal to start the engine, but worth considering if you’re trying to send other commands immediately following an ignition. Hope that makes sense.

This man speaks the truth. I would suggest you look at this thread:

If, like in my car, your sockets completely cut out when the key is removed you’ll need to go with a battery option but if they just temporarily cut out when the car is started or stopped then I would just put some big ass caps™ across VIN and GND so the core will survive a brownout

Ohhhh, ok. Now I’m following you on the breadboard. I had looked at a GSM relay ( before I discovered the Spark Core and it has screw tightening connections, and I had it in my head that the Core had those too. Yeah, I’ll use the breadboard that comes with the Core then.

This is the part that I’ll need the most help with I think. I’ll have to do some more studying the documentation and examples and then try to get a start and upload what I come up with.

Thanks guys.

Yeah, I am planning on using the cigarette lighter/power port. I know the power port below my radio in the dash does not put out power with the key off. There is a second power port inside my center console, and I still need to check to see if it stays powered. I’m pretty sure I can get some constant power from somewhere in the car if that power port doesn’t stay powered up.

I would think that once it receives that “push” of the start button, the engine will fire up and won’t matter if the Core loses power for a few seconds.

I’ve also considered using a usb battery pack if the car doesn’t power either power port without the key. I’d have to get one that allows pass through power that will power the Core while it charges from the car when the engine is running.