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I want to make my radar detector vibrate my seat

2864 Views 51 Replies 8 Participants Last post by  djdonte
I have my Escort Max360 hardwired with a smart cord. I sometimes have trouble seeing or hearing the alert between my exhaust and music. The vibrating module in the seat has to be a simple 12v motor. I’m no electrical engineer but I was thinking of a relay set up. I’m guessing the blue LED in the smart cord box is fed around 3v so I would need a relay to give the seat motor 12v from a 3v trigger. Does such a thing exist? Any ideas or input? Am
I crazy? I’m sure there is constant 12v under the seat for the motors. I am comfortable opening the smart cord box and soldering or whatever else I need to do, although I am hoping to tap into the wire between the box and detector for the trigger voltage for the blue alert light.

Here is the smart cord:
Escort Direct Wire SmartCord (Blue Light)
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I posted the two parts that will do what you want.
You could always rethink what you want to do and get a radar detector that has bluetooth, then just have it vibrate your phone.
The reason why you get 12 volts on the LED when OFF and 2.7 when ON is the circuit opens the GROUND path to the LED.

Connect the negative lead from whatever you are using to trigger (solid state relay) to the point that goes to ZERO (#1) and the POSITIVE of the trigger to #3 (maybe #4)

Most of these cars switch GROUND and not POWER in the mirror circuitry.
Or a resistor to step down the trigger voltage?
I would use a potentiometer and "dial it in" if I needed to.
Use the "high" range setting on the trigger and your should be good to go.
If you want to use resistors, you just need to measure the resistance from the wiper to the other terminals and then get two resistors and duplicate (close as you can) the two values.

You could also use a zener diode to drop the voltage to a range you can use.

Put it in series with a resistor (current limit).

I would use a 6.3 volt zener and a 1k resistor.
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Well screw me... The trigger wire gave off 8v when I wiggled the cord to make all the lights go off, but on alert during regular use it does not rise above 3. I drove it around and got some K band alerts and nothing. Ugh. I can make the detector go off for laser with my phone but it take a min to get it to work.

I ended up opening the box back up, soldering a wire to the + side of the LED. Now I have 2ish volts on alert, no voltage on idle, BUT on start up it gets 12v and also gets 12v if I unplug the RD while the car is on. Not sure what I am going to do, besides wire a switch to the trigger wire to control it. Its pretty annoying. The motor vibrates for 2-3 seconds on start up, and also if I disconnect the RD when stowing it, if I do so before opening the door to cut off RAP.

I wonder if there is a switched circuit that does not get RAP? If so I could power the relay with that, this way it wouldnt work no matter what comes thru the trigger wire.
As I said, these switch the ground, not the positive.

Use the negative side of the led for your negative connection to the relay.

Use #4 for the positive connection on your relay.

You could also try the positive lead from the LED as well.

In fact, you might just try connecting your solid state relay across the LED, it might have enough voltage to trigger the relay.
I’ll try that. The relay power supply needs to have common ground with the trigger. So I’m guessing both grounds goto negative LED, positive trigger to #4, positive relay supply to 12v accessory power?

The input does not have to share a ground with the power supply.

Treat the input circuitry separate from the output circuitry.


If you are using a solid state relay, the above applies.

You just use the voltage across the LED to trigger the relay input (it should be enough).

The relay output is your switch, one side to 12v positive, the other to a motor lead the other motor lead to ground.

If you wire both "grounds" of the relay together and go across the LED, when the LED lights you will smoke the current limiting resistor for the LED.
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Then you are not using a solid state relay.
Handwriting Font Parallel Rectangle Drawing

Ideally I would use one lead of the LED (anode) for the positive to the trigger. This will probably be positive all the time with respect to ground.

As for negative. Trace the other lead off the LED and see where it goes. It will probably go to one end of a resistor. Note, one lead off the LED is gonna go to a resistor!

The other end of the resistor is where to connect the other end of the trigger, negative, this IS NOT in respect to ground. This gets switched to ground when activated/alarm.

One thing you mention that on startup, it triggers.

This is because some units on start up default to a known state or LED test where all the LEDS light up/flash on turn on.
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Now you got it. Glad it works for you.

However, that is not a SS relay.

It is a coil relay driven by a transistor input.

A "real " solid state relay uses optical isolation and the input uses no reference or is isolated from ground, which is why you can put the input across anything and not blow shit up as no connection gets grounded.
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You say it works as is and no smoke.

"Blowing shit up" ok, here is the explanation:

Your coil relay has a connection to ground (negative) return, whatever you want to call it.

You are connecting that to the LED lead that goes to the current limiting resistor (in series) which goes to a device that switches it to ground, ergo the LED lights.

As you can tell, when triggered, the coil relay which has a 12 volt source, will sink current through the LED current limiting resistor as well.

If the current is enough, you get a POOF, and the resistor smokes.

It appears the resistor can handle the increased load, so I wouldn't worry.

If the circuit you are using had a dedicated ground/return and it was connected, then you would sink the LED current and it would go POOF (no current limiting).

If you do use the SSR, you may have to solder across the current limiting resistor to get enough trigger voltage.

You would not need the heatsink, unless your vibrate motor is a current hog.
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Thanks for the explanation. I will try the SSR when it gets here.
You are welcome. I use to get big bucks for figuring this kinda stuff out. lol
Haha. The solid state relay did not fire on 1.95vdc from the alert led. So back to the transistor relay.
Connect the SSR input across the resistor that is connected in series with a lead of the Alert LED.
That is the current limit/voltage dropping resistor for the LED.
You should get about 10 volts when the alert LED is lit.
That should give you plenty of voltage.
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