DIY Electronic Derailleur on Instructable

I’ve posted an Instructable showing how to build and install an electronic derailleur. If you like this project please vote on the Instructables page. A more complete and finished product including my bike computer is in the works.
For now the Arduino sketch, schematics, Fritzing diagram, bill of materials and CAD diagrams can be found on the github.


OBD-2 Testing Update

I finished testing the OBD-II adaptor board this week on a Toyota Camry. As you can see in the picture the board had a few bad connections, but nothing that couldn’t be fixed with a few jumpers.

I was able to get a number of stats from the free Torque Android app like
  • Throttle position
  • Engine PSI
  • Collant temperature
  • Engine Load
  • A number of Diagnostic Trouble Codes
  • O2 sensor voltage
  • Revs
One interesting note I learned was the evaporative system test reported as incomplete, which Toyota supposedly repaired during my last visit!
Next up, test the remaining OBD-II protocols and bluetooth range. Expect a new revision in a few weeks.

OBD-2 Build Update

I finally finished assembling the OBD-2 board yesterday. It has taken a while because I’ve been working on an exciting web app for hardware engineers, which will be launching in a few days. I will continue to update the schematics on github, but I don’t recommend building version 1.0. There are a couple of layout and footprint issues I want to workout first. Next up, testing.

Bluetooth OBD-II Adapter


Update: Here is the git repo

A couple of weeks ago my Dad and I were trouble shooting the cause of a check engine light on our 2000 Toyota Camry. Using an off the shelf OBD-II reader we got a warning about the EGR system. After trying every test in the book we came up empty and finally had to take it to Toyota. They found a sticky relay that was beginning to fail, which was hard to diagnose because the light would only come on after ~30Km of driving. If we had a way to monitor signals in realtime this problem might have been easier to solve. This is why my OBD-II board was created.

The board is basically the reference schematic for the STN1110, which converts many OBD-II physical layers into RS232. The bottom of the board has a bluetooth module from Deal Extreme. The plan is to connect a smartphone or tablet to the device and log data.

Similar devices exist on the market, but I couldn’t find any cheap ones that have the STN1110. Scantool offers a 3.3cm x 1.5cm module for $70, but that seems a bit expensive for a $10 chip.

Scantool’s module

The STN1110 is supposedly faster than the Elm327, which is good for realtime data logging. It  supports the following protocols:

  • SAE J1850 PWM
  • SAE J1850 VPW
  • SAE J1939
  • ISO 9141-2
  • ISO 14230-4 (KWP 2000)
  • ISO 15765-4 (CAN)
  • ISO 11898 (raw CAN)
My board is 5cm x 5cm, which means the pcb can be manufactured by Seeed Studio‘s for $10. I’ll post the schematics on git hub in the next couple of days.