Jabiru tachometer lighting coil alternatives

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stevejahr
Posts: 2
Joined: Tue Mar 28, 2023 4:42 pm

Jabiru tachometer lighting coil alternatives

Post by stevejahr »

EIS 6000 sw ver 78 as per first screen at bootup. Aircraft built 2011.

Tach has been working just fine... and then I installed the Rotec alternator thus losing the Jabiru lighting coil dynamo.
I also installed the Rotec electronic ignition with a dedicated tach output that I connected to tach 1 and set P/R to 3 on EIS.

Apart from the mag check dropping tach when Mag 2 disabled (the electronic ignition), this seemed to work just fine.

Then the other day, when things got warm, tach went away to zero. The electronic ignition was still functioning as per mag check but just no tach output from EIS. Landing without a tach is a bit distracting so I am re-investigating alternatives. Note that inspection of wires and connections found no anomalies and the tach is again working. Intermittent problems are the worst...

1. The EIS documentation seems to suggest support for two tach signals, at least in the most recent version. How do you know if your EIS really does support the tach 2 input? Is it ALL in the software version or was there some hardware also required?

2. The EIS documentation also suggests connecting tach to magneto P-leads via a 27K ohm resistor. Has anybody tried this with Jabiru coils and found it to work? This solution does not seem to be working for me and I would love to know if it is me or something that is known to not work?

I would hate to have to throw more $$$ at this thing to add in another Hall sensor just for the tach...
GRT_Jeff
Posts: 802
Joined: Tue Dec 11, 2012 12:11 am

Re: Jabiru tachometer lighting coil alternatives

Post by GRT_Jeff »

Did you change the Tach Sensitivity (Tach1Sen) to High? Electronic ignition tach signals are often low voltage and require the High sensitivity setting.

1. Tach2 requires hardware and I think it was added in 2009 along with version 75.
stevejahr
Posts: 2
Joined: Tue Mar 28, 2023 4:42 pm

Re: Jabiru tachometer lighting coil alternatives

Post by stevejahr »

Finally got back to this part of the project...

I had used Low sensitivity on both tach senses as the GRT documentation encourages this setting.

I found that setting the Tach2Sen to High enabled reading a tach signal from the Jabiru ignition coil P-lead with a 75K ohm resistor inline as per the GRT documentation. Then I needed to change the Tach2P/R from the intuitive 3 to 6 for the RPMs to match up to the electronic ignition tach. Apparently each flywheel magnet generates 2 pulses on the Jabiru ignition coil P-lead.

I also changed the Tach1Sen to High for the electronic ignition as suggested. As this was an intermittent problem I do not know if this resolved the problem but I do still have a tach from this source. I hate "time will tell" but that may be where I am at.

I do see momentary RPM number spikes as the EIS switches between tach signal sources...
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