car – Experimental Engineering

Posted on March 15, 2017April 24, 2017 by The Engineer — Leave a comment

Bargain Bin USB-ODB Interface

This is a little bit of kit I got to talk to the Webasto TT-V I salvaged from a scrap Jaguar S-Type, and converts USB-RS232 to the standard car diagnostic ODB connector. (These are a much cheaper option at £4 than the official Webasto diagnostic adaptor & loom which is over £90.

There’s really not much to this adaptor, the only signals that are routed to the ODB connector seem to be the +12v on pin 16, K-Line on Pin 7 & L-Line on pin 15. The main IC here is a CH340 USB-Serial interface, with some glue logic in the form of an LM339 quad comparator.

The reverse side of the PCB only has the power indicator LED.

Posted on March 4, 2017April 24, 2017 by The Engineer — Leave a comment

IC Decap – TDA3606 Multi Regulator With Battery Sense

This is a chip aimed at the automotive market – this is a low power voltage regulator for supplying power to microcontrollers, for instance in a CD player.

The TDA3606 is a voltage regulator intended to supply a microprocessor (e.g. in car radio applications). Because of low voltage operation of the application, a low-voltage drop regulator is used in the TDA3606. This regulator will switch on when the supply voltage exceeds 7.5 V for the first time and will switch off again when the output voltage of the regulator drops below 2.4 V. When the regulator is switched on, the RES1 and RES2 outputs (RES2 can only be HIGH when RES1 is HIGH) will go HIGH after a fixed delay time (fixed by an external delay capacitor) to generate a reset to the microprocessor. RES1 will go HIGH by an internal pull-up resistor of 4.7 kΩ, and is used to initialize the microprocessor. RES2 is used to indicate that the regulator output voltage is within its voltage range. This start-up feature is built-in to secure a smooth start-up of the microprocessor at first connection, without uncontrolled switching of the regulator during the start-up sequence. All output pins are fully protected. The regulator is protected against load dump and short-circuit (foldback
current protection). Interfacing with the microprocessor can be accomplished by means of a battery Schmitt-trigger and output buffer (simple full/semi on/off logic applications). The battery output will go HIGH when the battery input voltage exceeds the HIGH threshold level.

Posted on November 16, 2016 by The Engineer — Leave a comment

Mercedes Benz Temic Central Locking / Immobilizer Module Teardown

The other day I was given a random pile of car electronic parts from the scrap bin at the local garage, so I decided to do a few teardowns. This first one is a Temic Central Locking / Immobiliser module from a Mercedes van. Judging by the 125kHz stamped on the label, this also has RFID capability.

The casing just unclips, revealing the PCB. Surprisingly for an automotive module, there is no conformal coating on this (they’re usually heavily coated in protective lacquer to prevent moisture ingress).

The large IC from Motorola I’m assuming to be a microcontroller, but I didn’t manage to find anything from the markings. There’s not much else in here apart from some glue logic, and what I think is the 125Khz toroidal antenna in the top left corner.