Customers ask us to help do some unique things electrically in their cars. In most cases, we’re helping their classic car do something that their new car does. We were just asked how to get a foot operated trunk release mechanism. This is a pretty cool request. Everyone has seen the commercials for cars that let you open a trunk or tail gate with only your foot. You wave it under the bumper and the door magically opens.
On one hand, this is pretty simple. You can get a sensor, wire it to your existing wiring harness and get your trunk to pop when you waive your foot under the rear bumper. However, there are a few safety and security concerns that you need to consider. Our Infinitybox system makes managing this really easy.
Before we get to safety and security, let’s talk about sensors. You need some sensor that is going to detect the presence of your foot being waved under the bumper. There are really two different kinds of sensors to use: ultrasonic and infrared. For all intents and purposes, infrared sensors are more cost effective and easier to use in these applications.
The advent of the hacker movement has brought tons of cost effective infrared sensors to the market. You need to find one that is environmentally sealed considering that it will be mounted outside of your car. You also need one that has an adjustable range so that you can set it correctly. This picture shows an example of an infrared sensor found on Amazon. These work by emitting an infrared signal and measuring the amount of light that is reflected back by an object in front of the sensor. You can adjust its sensitivity to get the right range.
You need to choose your sensor based on the distance between the underside of your bumper and ground. The sensor above has an adjustable range of 3 to 15 inches. You also want to make sure that the sensor can operate in the 12 to 16-volt DC range. Lastly, you want a 3-wire sensor. This illustration shows typical wiring for these sensors.
You connect the black wire to ground. You need to get battery voltage to the red wire. The yellow wire is going to connect to an input on your MASTERCELL.
For battery voltage, we recommend powering this off an output on your rear POWERCELL that is on when security is disabled. That way the sensor only has power when you turn off security from inLINK. This will help to reduce the drain on the battery.
The yellow wire is going to a MASTERCELL input to trigger the trunk popper. You have to make sure that the sensor grounds the yellow wire when it is triggered. In most cases, this is called an open collector. Check the literature that came with the sensor or test it with a power supply and a multi meter.
You are going to have to set the range of the sensor to work properly with your car and your bumper. The sensor should be pointing down towards the ground in an area under the bumper that you can easily access with your foot. The sensor will have a screw on it that will allow you to set the sensing distance.
Here’s where our Infinitybox system makes this really easy. There are a few things that you need to consider with a foot operated trunk popper. First, you don’t want the trunk popping randomly as you drive down the road and go over an object. Also, you don’t want anyone else to be able to come up to your car to pop the trunk with their foot if security is enabled.
To handle these two issues, we can program your system so that the trunk popper can only work then the car is in park and when security is disabled.
Here’s how this would work. As you approaching your car, you press the button on your inLINK key fob to disable security. This is going to activate the sensor on the back. If the car is in park, the trunk will pop when you wave your foot under the rear bumper.
You can do the same thing with other doors. You can also do the same thing to control inMOTION outputs to drive a linear actuator to actually raise the trunk when you waive your foot under the rear of the car. This is just a simple example of some of the powerful things that you can do with your car wired with our Infinitybox system.