I started working on cars years before I was able to drive. My first project was the restoration of a 1971 Jeepster Commando. I have had several automotive projects since then, of varying levels of magnitude. One of my current projects is a 1970 Chevrolet El Camino. When I got the vehicle it was missing most of the interior, including the radio unit. I could have gotten an aftermarket radio or tried to find an original Chevrolet radio, but I decided to build my own so I could include whichever features I want and make it look however I would like. My finished radio will have an FM tuner, Bluetooth audio, auxiliary audio input, and most importantly will not look out of place in my 50 year old dashboard.
This is an electronics heavy project and exceeds the level of involvement I have previously had with electronics. My first stages of this project consisted of me learning about the electronics I will be using in this project and testing their implementation. No tangible progress came until I started ordering parts and materials. I am using an Arduino Uno for the control of the radio. It drives the LCD screen, and takes and interprets inputs from the knobs and buttons. A TDA7439 is used to switch between audio sources. It can select from up to four audio input sources. The IC can also make equalizer adjustments, such as bass, mid, treble levels, but I do not currently plan on implementing those features. The tricky thing about the TDA7439 is that it will not fit in a regular ol’ breadboard. It has smaller SDIP dimensions, rather than the usual DIP dimensions. To overcome this I got a little breakout board. I ordered two, which ended up being a good call because I fried a TDA7439 chip during testing and they are hard to unsolder from the breakout board. Radio tuning and RDS data comes from another IC, a Si4703. I got the chip from SparkFun. They also offer a Bluetooth audio chip, but it is expensive, so I opted for a less refined, but cheaper option. [more info about the BT solution] It does not provide any sort of play/pause/skip music control and does not provide information about the current track. The next component is a real-time-clock module, to keep time when the device is turned off. The real-time-clock module has a battery onboard, so time should be kept even if the car battery is disconnected. The last ICs used were two buck converters to bring the 11~14.6V provided by the car down to 9V (the TDA7439 requires 9V) and to 5V (the rest of the electronics require 5V). At the time of this initial posting I do not yet have all of the electronics in working order. I have been prioritizing the visual aspect of the project, as this is an aesthetics class, not an electronics class.
I took apart an old car radio and am reusing the housing and knob shafts. The main piece that has been designed an fabricated is the “faceplate.” It is comprised of sheet metal and acrylic. An inner faceplate part exists for mounting the LCD display. An outer faceplate part exists for holding the acrylic sheet and another piece of sheet metal. These inner and outer parts are both 26 gauge steel sheet metal. The acrylic is in front of the LCD display and will have markings. The front-most metal will have holes for two push buttons. I had a hard time deciding between having two or three buttons. I thought three would be nice to have, but may look too crowded in the space available.
I am not impressed with how the sheet metal turned out. Using tin snips to cut was a sloppy method. I am considering re-manufacturing the sheet metal parts with a mill before our class expo.
The radio face plate also features a piece of acrylic over the LCD screen. I used 0.050″ thick anti-glare acrylic for this and laser cut it. I tried engraving my desired design into the acrylic. It looked fine, but I think that having the design printed on paper behind the acrylic looks better.