Originally Posted by ykobayashi

I have finished my Tachometer Amplifier design. I was able to condense it all down to a poker chip sized circuit board.

I used @oldpokey’s circuit diagram and @Techguy512’s idea to use a RISC microcontroller to do DSP on the signal rather than analog signal processing using a LM1815 like VDO. Hats off to those gentlemen. I really spent a lot of time researching everything they posted here. They really put in a lot of work and I want to recognize their hard work here.

Even with their posts I still took a little over a month to get to this point. The design was challenging in a number of ways. I also haven’t done any electronic design after retiring a decade ago. I was very burned out as an engineer and didn’t want to look at another line of code or circuit trace. This design reminded me of why I used to love engineering.

I looked at Techguy512’s design over the years. I didn’t think it was a big deal till I tried to make my own version of it. He was a very talented engineer and I enjoyed following his design process. I wouldn’t have taken this on if he hadn’t left us. But I realized from this thread there isn’t a new OEM unit available anymore and there is a gaping hole left to be filled. I hope my version stands up to his.

Refurbished units are a great solution. I personally picked all the silicone off my old VDO unit in 2010 and resoldered every joint with fresh solder and flux. It has lasted till today. My remix of Techguy512’s design is a stopgap effort for those who cannot find a working JY unit or don’t want to refurb their old solder. Both solutions are a big jump over a cigarrette butt. I tried that in 2010 and didn’t have lasting results.

Parts are still coming in. Tentatively I’d like to offer the unit up for the same price Techguy512 did to our members. Postage has gone up a bit but parts prices have dropped since 2015 so I think it’ll all balance out.

Enjoy the video.

https://youtu.be/-CSxKbfhnNQ