Powering on/off aftermarket accessories using existing "switches"

[fgwinn]

I am planning to install a front view camera on my MY22 CT 4 to facilitate parking at the EA charging stations. My car does not have the factory installed surround view camera option. I am trying to decide on the approach to use for powering the camera on/off. I do not want to install a switch anywhere inside the cabin and I don't want to operate the camera continuously. Here are the possibilities I am considering. I am not certain if these options are really feasible and I invite any comments, criticisms, or suggestions.

1) Inexpensive timer relays like this one can be configured to turn on an accessory for a specified time after receiving a trigger signal.

https://www.amazon.com/gp/product/B083HN673G/ref=ox_sc_act_title_1?smid=A1YGHK4VRDPUC4&psc=1

Possible choices for a +12v trigger signal could be the horn, the light above the Sun visor, or one of the pins in the bicycle rack power socket. A tap on the horn or lowering the Sun visor could trigger the camera to display for five minutes or so. Depending upon what signals are available in the bicycle rack socket the trigger could be reverse gear, a turn signal, stepping on the brake, or perhaps even turning on the rear fog lamps. Engaging the front camera by shifting into reverse may seem silly, but if the timer is set to be on for five minutes it would definitely be workable.

2) I don't know much about external garage door receivers, but I think one like this unit could do what I am trying to accomplish.

https://www.northshorecommercialdoor.com/gurx5exre.html

The way I envision this working is that the receiver would be programmed to use the same signal as my garage door. When I am home pulling into the garage turning on the camera could be useful. When away from home the receiver would be used to start the camera. Since there is no timer function in the receiver, the camera would have to be manually turned off by pressing the garage door button again. Since the receiver has two channels, it would be possible to power on another accessory by programming another remote.

3) A combination of #1 and #2. The garage door receiver could supply the trigger signal to the timer relay. That way I would not have to remember to power off the camera.

Sponsored

 

[fgwinn]

I experimented with this garage door opener receiver I found at

https://www.northshorecommercialdoor.com/gurx5exre.html

and had mixed results. Since the Guardian receiver uses a different frequency than my Liftmaster door opener I had to also purchase a Guardian door opener remote to program the Homelink system in the car.

The Guardian receiver has some useful features that make it particularly suitable for use as a remote switch in the car. It has two channels with common, normally open, and normally closed contacts. Some other brands do not have the normally closed contact. The receiver also has the option to set the relays to pulse mode or latch mode. In latch mode the relay changes the state of the contacts until the remote is pressed again, or until the power to the receiver is cut. I am not sure about the current rating for the relays, but since the device I needed to power on and off draws less than 200ma I am comfortable using the receiver. I wired the camera and receiver to the same circuit by connecting the positive lead for the camera to the positive input lead on the receiver. Then I connected the negative receiver input contact with a jumper to the common contact of channel 1. Finally the negative camera lead was connected to the normally open contact of channel 1. Using the Guardian remote the receiver works flawlessly to toggle the device (in this case a front facing camera) power on and off.

Originally I only had one opener programmed into the Homelink system and was using the dashboard diamond button to control the garage door. It was easy to add the two channels of the Guardian remote to the Taycan Homelink system. Unfortunately, with more than one device programmed the diamond shortcut button can not control the garage door, instead it brings up the Homelink menu. Unlike the shortcut button, pressing an option on the Homelink menu requires holding the selection for a short period in order to activate the device. I can reliably do this 100% of the time with my garage door.

Unfortunately, toggling the Guardian receiver relays on and off was closer to 50% reliable. With the receiver channel set to "latch" mode, turning the camera on or off requires holding the Homelink menu selection long enough to power the camera but not so long enough that it cycles the power off. Combined with the lag in starting up the WiFi camera I decided that the set up would be too complicated to use. I suspect adding the timer relay (referenced) above to the output of the receiver (set to pulse mode) would be workable. Another option would be to use the Guardian remote to control the receiver.

For the time being I decided to install the camera with power from an ACC circuit so that it is on continuously. I will control the display on the phone from the camera app. If the camera holds up over time, I may revisit trying to get the receiver to work.

Hopefully some forum members may find this information useful for controlling other aftermarket devices.