Speedster Redux and the Zeva2 Fuel Gage Driver: From Analog to Digital

This week we go a little bit more in-depth with Ian Hooper's Zeva2 fuel gage driver.  I'm quite enamored of this little device which he apparently is still building by hand.  And improving.

In the latest incarnation, he's solved the fuel gage direction problem by using a 20 turn potentiometer.  The direction is indicated by which side of pot center you are on and the discharge rate, or really capacity of the cell, is indicated by how far from center you adjust it.

There are two other features I'm particularly excited about. First, it provides an instantaneous current indication as a series of pulses designed for a tachometer. A pair of little microswitches allows you to set your pulse count as in four cylinder, six cylinder, eight cylinder, etc. And the device automagically and with NO calibration puts out pulses to correlate 100 amps with 1000 rpm.

We set this up with a switch on the dash to switch either our normal RPM from the RECHARGECAR magnetic pickup on our motor, or this Zeva2 current output. I can switch between them at the press of a button.

I cannot express how much of a difference this makes.  Digital displays of rapidly changing current loads are just not very useful.  They update at the update rate of the display, and the result is just a dancing number, meaningless and without form.  When you put this on a BIG needle on a BIG gage, suddenly, it has all the missing rate and direction information - trend if you will.  We may only hit 1000 amps briefly.  But we'll get to see it.