Tacho 'un'booster

[RA35GT]

OK. Bit of a thread dig.

But I got the tacho in the MA70 working properly and just wanted to share in case anyone else has similar issues.

I cheated a little though, I didn't use the factory tacho output from the 1UZ ignitor (i.e. the flyback voltage style)

Since I had to change 4cyl-6cyl I used a Jaycar Speedo corrector with some mods so I could have different input and output voltages.

For the input I used IGT1 (which is a 5V square wave - confirmed via oscilliscope).

I set the speedo corrector to increase frequency by 50%.

Set the speedo corrector to active low and then you need to mod the board for a 12V pullup. (Don't need to change any components, transistors still operates in saturation).

(When configuring the speedo corrector ensure to set the input to no pullup or pulldown and low sensitivity. Also make sure to set it up so the display update is the quickest possible and in this case you also need to set it up so it makes the output frequency faster then the input frequency, this will all make sense when you have the speedo corrector)

Simple as that, basically four wires and bobs your uncle.
Magical black box LOL


working tacho
http://www.youtube.com/watch?v=Zs5DlAsx110
(mind my nephew screaming near the end lol)