RFID Remote Start/Alarm Schematic help

Thread Starter


Joined Apr 14, 2009
Hello, and thank you in advance if you can help with this one. You will need a good understanding of car alarms, remote starts, and electronics used. While I have a decent understanding, the technicals of this project I can admit is beyond me, so Im willing to pay if required for the help. I hope to learn along the way as well. So here goes:

The vehicle is a 1998 Subaru Impreza 2.5RS no factory security, the security system is a Scytek Visionguard 8000. 2 way alarm, remote start, video capture. I have a pdf of its owners manual/install instructions if needed. And a pdf of my cars electrical. The basic project is to use RFID to eleminate the need for a key, incorparate that into the scytek alarm with remote start. I will also be using a push button start (kinda). I hope you can follow my thought process.

I need help with:

1. how to wire into the door lock actuator to get the unlock pulse from when I disarm the alarm from the remote to turn on the RFID reader and remain on until lock/arm is activated again. I also need to know how to get the RFID to run off 12v since I cant seem to find a 12V setup?.

2. I need to know how to get the RFID reader upon succesful link to its key to enable the acc and ign circuit of my car.

3. How to use the battery isolator(s) to run off a switch, namely the DPDT Center Off Switch I have. One position (normally selected) selects battery one, the other position selects the other center is....off. As I understand it battery isolators are normally wired so one runs only when the acc is selected? Do you know if I have this understanding right? And if so, how do I incorparoate that into this setup? Ideally I want the center off to disable both batteries and up to enable my main, down to enable the aux. I need both batteries to get charged from the alternator, but I need the aux to not be able to be "over charged" since it will not be normally used

I have the simple(r), I hope, idea of simply hard wiring a spare keyfob behind a momentary switch to a constant 12v rather than the small battery that will need replacement and pushing on the "start" button is simply pressing on the "Start" button of the transmitter, activating the "remote start" feature of the security system. I am ok with the 2-3 second delay. The benefit is this already has a tach learn, clutch override, etc. Alls I have to do is have the RFID tag acting as the key and press the brake before I start driving to avoid shutdown. Leaving the vehicle or pushing arm/lock shuts down the cars RFID, thus shutting off the cars power and arming the alarm.
The RFID is essentailly taking place of the key turn to acc and ign simutaniously, and preventing theft from anyone who doesnt have the RFID key from being able to leave with the car even if they can start it. While hitting unlock will start up the RFID unit, the car cannot be started until a successful link with the fob. the alarm is providing the other security, however if power is lost, I can open the car with a key at the door and switch to the aux battery as discribed above and hit unlock to restart the RFID reader.
I hope that made sense and was easy to follow, and I hope you can help out.
Last edited:


Joined Feb 19, 2009
Which RFID Reader are you using? Most have only "near contact" range of a few inches or less. This would mean a module for the door and another for the ignition.

The keyswitch ignition controls a LOT of signals in addition to engine start/run. Remote start only switches enough to get the car running, but not "driveable".

Some new cars (Mercedes S550, Audi A4, others) are entirely keyless and only operate on the RFID "fob" which is always in your pocket. They have only a button on the dash with no keyswitch. They unlock when you walk up to them, get in, push on the brake, and push "Drive", it starts the engine and you drive. These are stolen quite often, although they use no mechanical key.

If it were a simple task, many alarm manufactuers would have it included with their systems as well.

Steve C

Joined Nov 29, 2008
This is cake and cheap if you accept passive RFID as your option.

A guy on ebay sells an RFID reader for $13 shipped, runs on 12 volts and is a simple digital output. 12V when sensed, float when not. (might be ground, I can't remember).

You hook that to three wires. #1, your door unlock. #2, your alarm "factory disarm" wire, or whatever wire interfaces to disarm the unit. If your alarm doesnt have this wire, you will need to crack open a remote and tie the unlock switch to it. This may make #1 obsolete. #3, you use it to fire a MOSFET. Or, you can make a push on, push off switch with a couple transistors. Or, you can use a timer/latch relay. lots of options.

Now, your remote start REQUIRES a transponder bypass to operate. This bypass is very simple. Will have a hot input that "bypasses". Or ground, however you set it up. Anyways, that timer/latch relay will activate the transponder bypass, just like activating the remote start.

Be sure to diode isolate the circuits. You dont want an unlock pulse from the FOB to activate the bypass. Only using the RFID scanner.


The electronics are done. Go to radio shack and buy an equipment knob for $3.50. get a $6 key copy and cut off the head. Epoxy it into the knob and leave it in your ignition.

No push button start is required. Also, no key is required. But only if you scan the RFID. You can place multiple antennas in the car wherever you want to sense.


Steve C

Joined Nov 29, 2008
Dont forget to buy a ton of tags from trossen. Carry a card in your wallet. glue a glass nodule inside your watch clasp. slip a paper disc inside your cell phone batery cover.

No matter where you are or what you are doing or what happens, you will be able to buzz yourself into your car.

And the knob is discrete enough it doesnt look like you left your key in the ignition.

Steve C

Joined Nov 29, 2008
By the way, I do NOT recommend a push button ignition. For these reasons:

#1. You still need a switch for ACC and IGN. This is goofy in every case minus the ignition switch. And the IGN switch already has a starter motor switch. Turn your wrist just a little farther and you are there.

#2. Most remote starts have an engineered delay to hit the starter. you will again look goofy if you press a button then have to wait 4 seconds while the car goes through a startup routine. Who knows. Maybe your alarm instantly starts the car. I'm betting it pauses for at least 2 seconds. goofy!


So forget the pushbutton start. Even BMW makes you push the key into a push-in, push-out slot to take care of ACC and IGN.

And you STILL have to HOLD the push button start to crank. Goofy! Like the remote start. The car should KNOW when to stop.

Steve C

Joined Nov 29, 2008

As you said, you've got backup systems in case of equipment failure. That is what you also have in the case of your OEM starter ignition switch. My transponder bypass key is not in a plastic box tucked up deep into the underdash. It is exposed, I keep it in my center console, easily accessible in case of any equipment failure. I can use that to start the car as the OEM intended.

Of course, it is not in a plastic box. It is in a lockbox used for realtors to lock up housekeys. A thief could definitely make my life miserable by taking that whole box and running away. But they will not get my car.