Years ago when the Bow Tie and High Button shoes were still in style there were several kits made for tachs and panels, even TXs. Just a few years back they still had how to articles for electronics in High Flight Magazine. {IMAA} Seems those days are gone now. My basic instructors father loved to make his own gear, I think I have one of his dads kit made tachs out in my shop still. The How To Dick found the thread for shows one basic problems for the DIY people of today, cost. For the price of the parts to make that tach I was able to buy a good TNC tach. I don't tell any sport pilot to go out and buy a TNC but I do tell folks new to the hobby to buy the combo tach and volt meter from Horizon. I have done side by side testing with my tach and the H-9 combo and so far haven't found one of them that didn't give true readings. Two good meters for the price of one. And you even need the volt meter!!