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Digital Tachometer for Harley Davidson Sportster (Part 15 - Issues during development and improvements)

Part1 / Part2 / Part3 / Part4 / Part5 / Part6 / Part7 / Part8 / Part9 / Part10 / Part11 / Part12 / Part13 / Part14 / Part15


  • First and main issue was.. how the hell do I make this project?! It was my first electronic project and I had to think & plan basically all the steps (quite stressful).
  • The J1850 VPN trasnceivers were discontinued and not available in the main online electronic stores. Luckily, I was able to find 3 IC on eBay and I was able to build my first dummy control unit that was broadcasting messages all the time on the data bus. For the final design I manage to replace the IC by a couple of transistors and resistors.
  • The lack of experience when soldering electronic parts and in particular SMD components. I lost 2 PCB on the way but I learnt the lesson to start always by soldering the most difficult components first.
  • I suffered many times problems on the PCB, usually due to my poor soldering skills that created micro joint cracks. I spent sometimes weeks trying to find the rootcause and that caused many times to loose hope.
  • Poor test & lab equipment, for example a computer 12V fixed power supply to simulate the battery of the bike. Anyway, I have to say that even with some basic equipment if you want to do something you can do it. With time I manage to buy a decent soldering station, a decent multimeter, scope, ….


  • The software still has some minor glitches that I don’t care to solve. For example, from time to time some number that should not be there appears on the gear indicator, but as fast as it comes, it goes away.
  • Need to implement the fuel consumption function on the tachometer.
  • Brightness can be increased or decreased by user request, except for the gear indicator that is fixed and it could disturb at night.
  • All the LEDs used on the RPM bar or on the mode indicator can not be seen when driving at daylight.
  • When the sun shines from the rear of the bike, it is not possible to read the 7 segments (even with full brightness).
  • Rear switch does not perform as expected sometimes. The connector should be improved.
  • 3D printed housing could be improved in many ways. It does not have a PCB fixing tab, only a position tab. Also it could be improved the hole on the back of the housing to avoid/reduce humidity entrance.
  • Design and print a vinyl for the tachometer cover. Currently, it has a printed paper that is now deteriorated due to the humidity and the sun.

Any other question or request, please leave a comment below or send me an email. Salut

Content: Homemade Digital Tahcometer for Sportster. Source: Momex.cat

Project index:
Part1 / Part2 / Part3 / Part4 / Part5 / Part6 / Part7 / Part8 / Part9 / Part10 / Part11 / Part12 / Part13 / Part14 / Part15

keywords: HD, harley, davidson, tachometer, tacho, tacòmetre, rpm, J1850, SAE, improvements, project, errors, problems, issues