I promised y'all some pictures as I experiment with the
Diesel Tiny Tach. If you just joined our broadcast, it's a digital tachometer with a transducer that bolts to an injector line... no W terminal needed. It acts like a tach but also has two service interval timers, a max RPM readout, and reverts to an hour meter automatically when the engine is off.
The display looks like this:
(yes my idle is a bit high... it's either that or I lose a filling)
The transducer bolts to an injector line with two small hex head machine screws. In this picture I've bolted on another terminal (bright pink) so that I can attach an oscilloscope probe:
Here's the output signal from the transducer at about 1100 RPM for all you geeks out there:
It's a pretty typical piezo transducer signal... a damped oscillation with amplitude about 60V and a period of 27 mS (37 Hz)...at this RPM... once per every two revolutions as injector #1 fires.
37 Hz / 2 * (60 seconds per minute) = 1110 RPM... cool dat.
It is a nice strong stable pulse, so the next step is to develop an interface circuit so that it can drive a standard timing light. With the right multiplier circuit it should be able to drive a gasser or diesel tach just fine as well.
The price for the entire unit has gone up 30 bucks since I bought this one, but the tranducer alone is still evidently quite affordable, particularly if it can become a timing light as well.
Other observations:
- the display is a good size and is backlit at all times
- having said that, the display is not really flush-mountable on the dash without wires showing etc. Not really an automotive form factor.
- the display has a pretty fast update rate (half a second or so) so great for monitoring RPM, setting the idle and max speed, etc... but probably too slow IMHO for shifting
Will post again when I have some circuitry developed.
Vince