Custom clip-on digital speedometer

[jangell]

My speedometer breaks angle drives after 5 miles, so I haven't had one in a long time. I plan on doing a custom digital dash, and had bought a Porsche 930 VSS ring and a 55505 Hall sensor as FABombjoy had done in another thread (http://dmctalk.org/showthread.php?16622-Bye-Bye-angle-drive!&p=236120&viewfull=1#post236120), and finally got around to doing something with it.

I used an Arduino to count the time between teeth, and output that to an Adafruit seven segment display in a 3D printed case clipped to the binnacle. This works quite well, or does now, once I added a filter function, switched to a shielded cable from the hall sensor, and got an accurate tire size. It updates every 1/8th of a second and does so with pretty good precision (as compared to my phone's GPS speedometer app) and doesn't jump around much at all.

I've detailed everything on my website (http://www.tmproductions.com/repairs-and-maintenance-blog/2019/9/27/digital-speedometer), and provided the Arduino code and STL files for the case, and links to the relevant parts, in case anyone else wants to see what I did. I could have driven the manual speedometer with a motor instead, but I'll be removing the speedometer when I do my digital dash, and I had the display lying around so I decided to do this. It is an intentionally somewhat crude build, since it's only intended to be temporary (I mean, the Arduino is sitting in its cardboard box under the passenger seat for now). I kind of like it, though, so once I might keep it around even after I finish the digital dash.

-- Joe

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[Josh]

this is really cool. thank you for sharing.

[CriticalB]

My speedometer is in need of calibration and to avoid the hassle I bought a replica BTTF digital speedometer I found on eBay that uses a quick refresh GPS. It has a dimmer switch for night driving, but the bright red lights are still kind of a distraction. Your blue lights may not be as much as a problem at night, but I found these LED dimming sheets on Amazon (https://www.amazon.com/Dim-It-Light-Dimming-Sheets/dp/B006R0VWSG/ref=sr_1_1?keywords=LED+dimming+film&qid=1570035221&sr=8-1) that make a huge difference. It's static-adhesive and as a bonus it masks the unused portions of the 7 segment display.

[jangell]

That looks promising. A big problem is the part of the display that isn't the LEDs, which limits the contrast between the display and the body of the seven segment display. Those dimming sheets might solve that too. Thanks!

-- Joe

[jangell]

That worked pretty well, CriticalB. It dims it down quite a lot, but I can still raise the brightness a little more to compensate. In daylight you can only see the blue digits shining through -- the white/grey casing around them is completely obscured by the black dimming sheet. I had to use some double-side tap to stick it on, as the electrostatic adhesion wasn't working at all.

Thanks!

-- Joe

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