Hello,
I'd like to get some feasibility feedback for my newest project which is taking shape at the moment.
It's a radio muting device for my car which also incorporates aftermarket Chinese rear parking sensors, like these here:
The general idea is that when you put your car in reverse, the muting device will switch the radio's phone mute pin to GND, which then turns off the volume. This is so you can better concentrate on parking your car and so you can hear the beep from the sensors better.
When you then get out of reverse, the radio mute is deactivated either on its own after 30 seconds, or by moving forward at more than 12 mph, or by turning your radio's volume knob a few notches.
So far so good, I've actually implemented this already for my daily driver car which has factory-installed parking sensors,, and a standalone circuit based on an ATtiny85 has been doing its work for a few years now without a problem.
Now, however, I would like to install rear parking sensors in my summer/enthusiast car, a 1998 MG F, as well. While I am at it, I want to integrate my radio mute circuit with the Chinese parking sensors I got off eBay for around $15 for this project. I'm also going to have to port my tried and true ATtiny85-based circuit to an ATtiny84, which will be needed because there will be a few extra pins necessary.
So this is what I have come up with:
(click on the picture for a full-size image)
The way I am going to tap into the Chinese parking sensors module is simply by connecting its beeper output pin (which does nothing but go HIGH to 5V and that way powers a buzzer) to an input pin of the ATtiny, and when the parking sensors beep, I will tell the ATtiny to output a tone on a subminiature speaker. The speaker will also be needed for signal tones from the muting device itself. The advantage will be that there will be only one speaker outputting signals both from the sensors and from the muting device itself.
There are other approaches on the web where people have actually managed to make sense of the sensor data that you can get off the parking sensors module via serial connection, but my sensor module somehow behaves differently and I have not been able to parse the raw data in any way that made sense and would have been usable directly by the ATtiny. So in that sense, my ATtiny is just going to parrot the beeps it gets from the parking sensors.
I haven't quite done much with the ATtiny84 so far, although I bought a few at some point for a project that didn't happen, so I am mainly interested to know if my pinout in the schematic is feasible. But all other questions and suggestions are welcome as well.
- carguy