WELL!!! I have not have a lot of time to dedicate to this project until I hurt my back several months ago. Been off work ever since and had surgery 3 weeks ago. I had plenty of time after the surgery and actually going crazy with nothing to do. With all this time available I finished the first prototype and want to share it with those who may be interested.
I did not want to design a transmitter and receiver when these things are available from many sources so I purchased a set off eBay for $13.50 from China. There is no way I could build the set for that price.
Next I designed a digital board that could be interfaced with the receiver. What this board does is; it checks to see that there is a signal from the Toad (via the receiver) and also checks that the brakes are being applied in the RV (via the RV brake light switch). There is a green LED for each function. If both green LED's are illuminated everything is OK. Should only one of the green LED's illuminate the board signals the driver by a red LED and also sounds a Sonalert speaker. The transmitter in the car connect directly to the cars brake light switch so anytime the brakes in the toad are being applied the transmitter sends a signal to the receiver in the motor home. So should the brakes be stuck on for whatever reason the transmitter sends a signal. If the motor home brakes are also being applied then the unit is happy. The monitor can be connected to any car and any auxiliary braking system.
Here is a picture of the Receiver unmodified, a picture of my board and a picture of my board installed on the receiver.
Here is a closeup picture of my board installed on the receiver.
Here is a picture of the modified transmitter and receiver mounted in there cases.
I am going to spin the board again to add a switch that will silence the receiver in the event you are not towing. I wish I would have thought of this prior to ordering PC boards... Oh well, live and learn.
I feel this approach to monitoring the braking system is much better then looking in my backup camera to see if I can see the LED bar provided by SMI. Half the time I could not tell if the LED's were illuminated or not. And I almost never looked at the backup camera to see if the brakes were being applied unless I was applying the brakes in the motor home. I do not think I could caught a failure in the event there was one. With the wireless system I feel much more at ease.
Thanks for looking, ~ Bill