August 26th, 2009

Mini-car Light Installation

Mini-car Light Installation

Toy cars are something that everybody has encountered during the childhood and even a non-car enthusiast like myself has had his share of toy car playing, racing, garage and road building and all that good stuff. You’d think that something like this would be more suited for kids, but what if you’re a grown-up, you have a small car at your disposal AND possess the knowledge to make some cool hardware improvements? That’s right, awesomeness occurs!

This is a DIY project that enhances a Kyosho Mini-Z car with some incredibly useful features: front, rear and under car lights! The model is actually a VW Golf R32 and, as you can see from the picture, it looks terrific, in true Fast and Furious fashion. The lights are LEDs, two white ones for the front, two red ones for the rear and two bars with 4 LEDs for under the car. The circuit keeping them all on uses a NE555 timer that generates a delay and keeps them on regardless of what the car is doing. Other parts include three capacitors, three resistors and three diodes (you can find a complete parts list and detailed schematics in the link provided, as well as other cool pics).

This is a truly astonishing piece of art, soldering a bunch of LEDs on a toy car, especially with the blue under car lights. If you’re a girl, then I suspect this amazing achievement of science might appear… uninteresting. But if that’s the case, then perhaps an LED Heart of Love would be more appropriate.

Mini-car Light Installation: [Link]

August 25th, 2009

AVR J1850 VPW Interface

AVR J1850 VPW Interface

Yet another car related project, this is the AVR J1850 VPW Interface which was designed as an On Board Diagnostic tool for car monitoring. The brain of the device is again the ATmega8 AVR microcontroller from Atmel, with 8KB of flash memory (this is more than enough for all kinds of features, since the basic source code is only 3KB).

The device supports serial RS232 for connection with the automobile, different baud rates (varying from 9600 to 115200 Baud), 4 different bus monitor functions and can handle header messages of 1 and 3 Bytes long. The circuit was designed for a single layer PCB and, starting with firmware 1.04, the device has a crystal 7.3728MHz. The controller is programmed using the ISP connector.

The interface has been tested with various ODB software, including, wOBD, Scanmaster and many more. A .pdf file containing the schematic, parts list, bill of material and other information regarding this project is available in the link below, as well as the source code, released under GPL.

AVR J1850 VPW Interface: [Link]

August 24th, 2009

Becker Unilink

Becker Unilink

Yesterday I wrote an article about an Atmel based Sony Unilink interface and today it’s another Unilink project, this time based on Becker car radios. For those who do not know, Becker is an important manufacturer of car radios and car navigation devices and it’s based in the UK. Becker made the first car radio, the first microcontroller car radio and the first car radio with CD player and has quite a lot of other achievements.

Becker’s version of the Unilink protocol is very similar with Sony’s in terms of hardware, but different in software. The good thing about this is that you only need a different connector and source code with Becker support. The model presented here is a Becker Monza 7882, a European model, with two DIN-ISO connectors and a Mini-ISO connector field (the picture above illustrates the pinout for this model, you will also find the complete pin listing and additional information).

The MCU used is the ATmega8 from Atmel and the schematics are available for download. The source code was written in C and is also available in the link below (there is a logger only version, an interface version and a modified source code for Becker Mexico 2330). The files are released under GNU General Public License.

Becker Unilink: [Link]

August 22nd, 2009

Atmel based Sony Unilink

Atmel based Sony Unilink

The Sony Unilink protocol is usually meant to control the CD-player of an automobile and can also perform other various tasks. The Sony Unilink protocol can be used to connect other auxiliary devices to your car stereo (these devices vary from CD shuttles to iPods).

This project is an AVR Sony Unilink interface based on the Atmel ATmega8 microcontroller. The MCU runs at 7,3728MHz and the communication with the Unilink bus is made through Serial Peripheral Interface (SPI) and the software supports RS232 input and output. The source code was written in C and the files as well as schematics are available for download under GNU General Public License in the link below.

(Another Unilink interface project entitled GNUnilink, based on the PIC16F628 running at 10MHz is also presented under GNU License).

Atmel based Sony Unilink: [Link]


The idea behind this project was born when a friend asked me too take a look at he’s broken GPS unit (MyGuide 3000) to see if I can fix anything. I started checking various parts like voltage regulators, but found nothing wrong. The gps unit was still not powering up so I checked the cpu, an ARM9 from Samsung and found it broken. Of course I couldn’t do anything about that, because of the BGA package and the bootloader needed after replacing it so the gps unit became a source for parts. The most useful and interesting parts from the GPS were the LCD display and the GPS module.

The GPS module is a RoyalTek RGM-3550LP which has an integrated antenna and is powered by SiRF Star III technology. I immediately connected the gps module to my computer’s serial port(using a max232) to test if it was still working. To my surprise the gps module was working and sending NMEA compliant sentences. Then I had this idea of using the gps module as a navigation system together with a notebook computer, but notebooks don’t have a serial port so I had to use a UART to USB bridge.

RoyalTek rgm-3550lp-gps-module

The most common used UART-USB bridge is the FT232 manufactured by FTDI which is about $4 which is a fair price because you don’t need any external parts for this chip except some bypass capacitors and that saves you time and money. I never used the chip before but it was really easy to get it working. It even has this custom utility that let’s you program some features saved in the internal EEPROM like the maximum bus power and the product and manufacturer descriptor strings. Anyway these are the only two settings that I tinkered with, but the utility let’s you change some more stuff.


The next thing I had to worry was where to get the power for the GPS unit, because it needs 3.3V and the acquisition current is 50 mA. The FT232 has an internal voltage regulator which provides 3.3 V and 50 mA but I decided not to use that in order to extend it’s life so I ended up using the TPS2148 which is a 3.3V LDO from Texas Instruments. It’s specifically designed for USB peripheral power management, and it’s tiny package(MSOP-8) made it ideally for my application. The TPS2148 handles the current limitation so I didn’t had to worry about that either.


After figuring out the parts I was going to use and the schematic, I had to chose an enclosure for this project. The main target was to get it as small as possible but the limit was the gps module size, I couldn’t of got it smaller then the module :). So I went and searched for a plastic enclosure, and I found one just perfect for what I needed, the PP85D from Supertronic. The gps module fits just nicely between the screw channels.

Then after I got the enclosure, I made the pcb using the photo etching technique.. I assembled and tested it, and to my surprise everything worked just fine from the first try. I’m usually not that lucky when I make stuff using new IC’s that I haven’t used before. Sometimes I don’t pay enough attention to the datasheet and I get some small stuff left behind and that messes my entire circuit. Anyway, happy as I was that everything worked from the first try, I put everything inside the enclosure and snapped some pictures of it. As a final note, this was a great project which I enjoyed making, and I really recommend you do something like this if you have a gps unit laying around.

more pictures:

parts-for-the-usb-gps-project gps-module-and-pcb ft232rl-board

board-inside-the-enclosure pcb-with-gps-module-inside-the-enclosure new-hardware-found

parts list:

  • RGM-3550LP gps module x1
  • FT232RL x1
  • TPS2148 x1
  • capacitor 10uF x3
  • capacitor 100nF x3
  • led x1

schematics and board files were designed in Eagle and can be downloaded here.

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