Strange Plane Power Alt + EIS problem

[lucky333]

Its not for airplanes. On carburated autos, the automatic choke is frequently actuated by a bimetal heating coil connected to the choke linkage. When the engine is started, power is applied to the heater, here by the voltage regulator when the alternator kicks in. As the coil gets warm, it uncoils and opens the choke. By the time the choke is open, the engine warmed up enough to run with the choke open. GM carbs and lots of others used them, including a lot of Japanese cars which is why this particular Nippon Denso alternator has the driven output. Alternators originaly intended for FI or manual chokes would have a different configuration. That's why its important not to assume that all alternators are the same internally, even though they might have the same physical appearance

John

[lucky333]

Here is about all you need to know about the Nippon Denso Alternator that Kevin seems to be using. Includes a schematic of the regulator itself as well as lots of good troubleshooting techniques that would apply to others as well.

Just the thing for a little light poolside reading

Nippon Denso Info

John

[kevinh]

Originally Posted by gmcjetpilot

Hummm I might consider doing the same to save another hole in the panel, especially with a "optoisolator". Did you really use a optoisolator? If so how did you wire that in? What aux scale factor and offset did you use?

PS don't feel bad TShort, I had to look up "optoisolator" also. My suggestion is google and Wikipedia.

Yah, I did. But like I said, mostly because I didn't want to deal with relabeling my pretty panel. If I was going from scratch, I'd probably put in the bulb and be done with it. I forgot to explain the context on wiring up the isolator, because my original post/thread intent was just to make people aware of a potential difference (hah!) between the Van's and PP variants.

In fact, I just checked the
Wikipedia link (thanks George) and it is a really good description of approximately what I did. I just drive the LED from the 12V output on the PP alt, and hook the transistor up as a gate to pull the EIS input between 4.8V (provided by the EIS) and ground.



I picked R2 as something largish (20Kohm? - don't remember) - the exact value doesn't matter, but smaller values will consume more current just for the pull up resistor. Ohm's law IR=V, where V is 4.8V.

For R1, it is operating as a current limiting resistor. To calculate that value, refer to the datasheet for your particular isolator. It will say something like 3.4V @ 20 mA. Approximately, this is specifying the ideal current and voltage for the LED to operate at. Either use ohms law for a series resistor or plug these two numbers in with the 14.1V typical max voltage for the alternator into one the common online calculators.

I would quote exact values, but they are in my notebook at the hangar - besides, they depended on the values I read off the back of the particular isolator I was able to find at the local electronics part megamall (gotta love Silicon Valley).

For AuxSF and AuxOff, I left them at the defaults of 100 and 0. Then powered the plane up (but did not start it). Verified that the alternator had pulled the LED on with a multimeter and saw that the EIS was showing a value close to zero (15ish). The I started the plane up and saw that the EIS was showing something close to 90 (because the transistor in the isolator wasn't pulling to ground). I then repeated same test, but start the plane and never bring alternator on, see that EIS is reporting 90ish. Therefore I set the EIS warning as a minimum of 50 (very similar to how I was using the it with the Van's alternator).

In my case I had a little circuit board serving some other data conversion purposes already hooked to the EIS (converting the EIS serial out into a form acceptable to the GNS430 for fuel flow/remaing data), so it made a nice place to install the isolator.

Or just use a bulb in the panel.

[kevinh]

Originally Posted by lucky333

Here is about all you need to know about the Nippon Denso Alternator that Kevin seems to be using. Includes a schematic of the regulator itself as well as lots of good troubleshooting techniques that would apply to others as well.

Just the thing for a little light poolside reading

Nippon Denso Info

REALLY COOL. Thanks!

[kevinh]

One more idea:

I bet one could do the math and change AuxSF and AuxOff to 'flip' the indication so that the AltFail value would show 100 for failure and close to 0 for no failure. However, I'm probably not going to get to this until the winter forces me way down on the 'to-do list.'

[lucky333]

Originally Posted by kevinh

One more idea:

I bet one could do the math and change AuxSF and AuxOff to 'flip' the indication so that the AltFail value would show 100 for failure and close to 0 for no failure. However, I'm probably not going to get to this until the winter forces me way down on the 'to-do list.'

You could get the same result by either picking up the LED source across the ALT FAIL bulb or putting the output resistor (R2) from the emmitter to ground on the output side of the opto and picking your signal off there. (Tie the collector to the +5 from the EIS).

Either way will remove the inversion inherent in the standard circuit.

John

[kevinh]

Originally Posted by lucky333

You could get the same result by either picking up the LED source across the ALT FAIL bulb or putting the output resistor (R2) from the emmitter to ground on the output side of the opto and picking your signal off there. (Tie the collector to the +5 from the EIS).

Either way will remove the inversion inherent in the standard circuit.

Good point! doh!