Fluctuating RPM Problems Solved

[vlittle]

I've been flight testing my design for a device that stabilizes the p-lead tach pulses from magnetos.  As often reported on this forum, it can be difficult to find a stable sweet spot by choosing the right resistor value in series with the SkyView's RPM inputs.

I published a preliminary schematic on the forum.  Now, the production version is complete and will soon be available as an open-source design, kit or finished device at MakerPlane.org.

This device works with any magneto p-lead input and generates a 5V compatible tach pulse.  It is a better choice than a variable reluctance pickup mounted on the magneto or tach drive because it is not attached to a hot, shaking engine.  The device is simply tie-wrapped onto an existing wiring harness on the cold side of the firewall.

See the pics.

Cheers, Vern

 

[rvator51]

Great idea Vern!

Cheers,
Tom Velvick

 

[vlittle]

Update, the P-TACH has been released and is now available from MakerPlane as a finished product, kit or open-source design.

http://makerplane.org/?p=1679

This thing really works, it eliminates the headaches of fine tuning the p- lead resistor and fixes the applications where there is no sweet spot. In my Harmon Rocket, it eliminated the spurious RPM overspeed alarms on take-off or descent. Intra-cylinder pressure affects the p-lead waveform, so a device like this comes in handy.

Vern