Stealth power-up: using a reed switch and a magnet

Sommelier

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After the inconspicuous buttons and morse code, I came up with this.

The neodymium magnets are extremely powerful and the reed switches pretty sensitive so you could hide the latter under a plastic part and still activate it with the magnet.
There I light up the orange LED for demonstration purpose but, of course, you'd rather want to control a relay to power-up your detector/jammers:

https://www.youtube.com/watch?v=8Q_Cyx11bis


This is the (crude) code I used, you could modify it for something more elaborate (e.g. do morse code with the magnet):

Code:
void setup() {
  Serial.begin(9600);
  pinMode(A5, INPUT_PULLUP);
  pinMode(13, OUTPUT);
  digitalWrite(13, 0);
}


void loop() {
  if(analogRead(A5) < 500) {
    digitalWrite(13, !digitalRead(13));
    while(analogRead(A5) < 500) {
      //Nothing
    }
    delay(200);
  }
}
 
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Deacon

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Nice! I think that's a great idea. The main question is going to be whether you need to keep the magnet in place to keep the power flowing. If you could use the magnet to activate the reed switch to simply tell the circuit to flip its position (open to closed or closed to open), that would be good.

I had a Miata for a while. Super fun little street-legal go-cart. But as a convertible, it was very vulnerable to break-ins. So I took my garage door opener apart, soldered it to a momentary reed switch, and stuck it behind the plastic panel under the steering wheel. That way I could hold a magnet to the area, and my garage door would open, but it looked like nothing existed to anyone walking by, even with the top down and even if they looked really hard and really closely. Even if the rifled through my center console and glove box, there was no garage door opener for them to steal and come back to my house.
 

Sommelier

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Great tip about the remote control!
Alternatively, you could wire a relay in parallel of your high beams or fog lights and have your garage door open at the flick of a (factory) switch.


Nice! I think that's a great idea. The main question is going to be whether you need to keep the magnet in place to keep the power flowing. If you could use the magnet to activate the reed switch to simply tell the circuit to flip its position (open to closed or closed to open), that would be good.
Well, that's what I'm doing in this example: approach the magnet and it turns the LED on. Take it away, it stays on. Approach it again and it turns it off.


You could very simply want the opposite behavior as well: have the RD on while the magnet is near the reed switch and take it (the magnet) with you out if the police want to search your car. El cheapo privacy-key-style.
 

wirelessandy

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Well, that's what I'm doing in this example: approach the magnet and it turns the LED on. Take it away, it stays on. Approach it again and it turns it off.
I was going to suggest that: A toggle-style switch with LED light feedback.

I've also done the stealth thing with my garage door. I've torn apart a garage door transmitter and I have a hidden hardware button to send the signal.
 

Deacon

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Yeah a discrete physical momentary switch works well for that purpose :)
 

Deacon

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I agree, it's probably best for other applications like garage door openers :)
 

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