Review on Effortless Car Control: PolarLander Universal Wireless Steering Wheel Controller for Music, DVD, GPS Navigation, and Radio - 4 Key Remote Control Buttons in Sleek Black by Nick Whitman

Ordered to include in a Raspberry Pi car audio/navigation project and first impressions are good. The instructions that come with it are a bit chinese but understandable for anyone with basic wiring knowledge. As the seller points out, if you want to use this with a pre-built or factory stereo, it needs to support two remote inputs and support code learning. The transmitters are 35mm (1-3/8 inch) in diameter and weigh less than 13g each. They run on CR2025 batteries (the one that came with it was dead on arrival but the transmitter worked fine after replacing it). The receiver is a small box that you can mount under the dash, it draws negligible current at 12 volts and has two KEY analog outputs that are typically 3.3 or 5 volts (switchable) and drop to a lower voltage, when a button is pressed. The transmitters are latched for battery access and have a pretty solid circuit board with tiny tact switches for each button. Several 3M adhesive pads are included to hold the remotes in place. The latches will probably wear out after a number of battery changes and if you pull the board out then all the buttons will fall out and it can be assembled in different orientations so you can get a different button layout if you're not careful. A decoder chip with 10 digital outputs driving some transistors and resistors to create an analog voltage output. Nice hack if you want to use this for something other than its intended purpose. I will not use the receiver, I will take the codes directly. For anyone wishing to do this, the system operates on the standard 433.92MHz frequency and transmits a 32-bit code made up of a 16-bit Transmitter ID, an 8-bit Keycode and an 8-bit -Counter that is incremented each time the button is pressed. can distinguish between single presses or press and hold. Codes are continuously transmitted about every 80ms as long as the button is held down, and there's no separate "unlock" code - you'll have to figure it out over time.