Electroair EI spark advance signal connection

Post Reply
Airdog
Posts: 17
Joined: Mon Jun 27, 2016 4:30 pm

Electroair EI spark advance signal connection

Post by Airdog »

I'll be installing an Electroair electronic ignition on my engine that has a wire lead coming out of the control head harness for a spark advance meter. In talking with Electroair, apparently seeing the actual spark advance is out of vogue and they no longer sell the meters, which I immediately thought should not be an issue since I'm fairly sure it should connect up to an AUX port on the EIS (if it's 5V) or to an Analog port on the HXr EFIS (if it's 12V).

So my first question is: can I hook up this spark advance meter signal to my GRT system [every 0.01 volt output = 1 degree of advance]. I was remiss in finding out if the spark advance meter lead outputs 12V or 5V. Please correct if I'm wrong, but I'm thinking if it's 5V I can connect it off of the EIS4000 as an AUX input. However, it's 12V I would then have to connect it to the HXr EFIS as an ANALOG input?

If it can be done, could you help me on how I need to configure the EIS/HXr to do so? I looked in both manuals but could not glean enough info from either one that would allow me to configure it (without massive amounts of trial and error at least!)

Thanks guys.... love your products!
Wade
GRT_Jeff
Posts: 660
Joined: Tue Dec 11, 2012 12:11 am

Re: Electroair EI spark advance signal connection

Post by GRT_Jeff »

The EFIS inputs aren't designed to be accurate to 0.01 V, but if the voltage is ever above 5V you have to use the EFIS or divide the voltage down.

Analog # Function: Aux (EIS compatible)
Analog # Internal Pull-Up: Off
Analog # Scale Factor: 250 (this will scale 0.01 V to 1)
Analog # Offset: 0 (0.00 V will show as 0, no offset, see the formulas below)
Analog # Sensing: Forward
Analog # Integer/Decimal: Integer (whole degrees only)
Analog # Aux Function: Aux
Analog # Aux Name: (Give this input a name for alarms and bar graphs)
Optional:
Analog # Remote Channel: (pick an unused channel 1-16 if you want to send this input to another display)
Configure a data box or bar graph to display this input.

You can check the input voltage and set digital filtering levels in SET MENU, Display Unit Maintenance, Analog Inputs.

SF = Scale Factor entered in EFIS or EIS
OFF = Offset entered in EFIS or EIS
VOFF = Value offset computed from OFF
VALUE = Computed from VOLTS, SF, and VOFF
DVALUE = Displayed value after applying the Integer/Decimal setting

If OFF is an even number:
VOFF = OFF/2
If OFF is an odd number:
VOFF = (OFF+1)/-2

If Sensing is Forward:
VALUE = ROUND(VOLTS*SF/2.5 + VOFF)
If Sensing is Reverse:
VALUE = ROUND((5 - VOLTS)*SF/2.5 + VOFF)

If Integer/Decimal is Integer:
DVALUE = VALUE
If Integer/Decimal is Decimal:
DVALUE = VALUE/10
Airdog
Posts: 17
Joined: Mon Jun 27, 2016 4:30 pm

Re: Electroair EI spark advance signal connection

Post by Airdog »

Awesome, thanks Jeff!
Airdog
Posts: 17
Joined: Mon Jun 27, 2016 4:30 pm

Re: Electroair EI spark advance signal connection

Post by Airdog »

Ok, more inquiry here since I got an answer back from Electroair.

Here's the statement from Electroair: the spark advance feed "is going to just produce a voltage in the range of 0.0V to 0.50V. The voltage output corresponds directly to the spark advance angle. For example, 0.25V equals 25deg BTDC, 0.30V equals 30deg BTDC, and so on."

Further clarification confirms 0.01V = 1 degree BTDC, 0.10V = 10 degrees BTDC. However, the normal spark advance range would be between 0.25V and 0.40V.

With this knowledge in hand, I propose to simply hook it up to one of my open AUX inputs on my EIS since it clearly doesn't bust the 5V limit for the EIS AUX port.

Also, please forgive me for any added effort, but what would be the configuration settings specific to the EIS?

Thanks again!
Bobturner
Posts: 429
Joined: Mon Mar 11, 2013 6:34 pm

Re: Electroair EI spark advance signal connection

Post by Bobturner »

I’ll just stick my nose in here. I think you want to know advance to better than 1 deg. Jeff says 0.01 volts cannot be measured reliably.
Airdog
Posts: 17
Joined: Mon Jun 27, 2016 4:30 pm

Re: Electroair EI spark advance signal connection

Post by Airdog »

Bob, I would like to know my spark advance on whatever EI it can be measured/displayed for, but I've never thought about wanting to know it out to a decimal point. Any discussions I've had or been privy to on discussing engine timing has always been regarding a simple integer number. But I certainly may be missing something! Not to get off topic, but can I ask why I would want to know advance better than 1 deg?

Also, since the standard range will most like result in voltages of 0.25 and 0.40, if there is no distinction between, say, a 0.26V value (26 deg advance) and 0.29V (29 deg advance) then it's not worth the trouble of hooking it up.

I may have misread Jeff's notation, but with his included instructions I read it so that 0.01V --UNSCALED-- cannot be measured reliably. What I don't know is what the scale factor does exactly in this configuration ... it sounded to me as it does what scale factors do in general: a sort of multiplier to scale the number up to a usable value that the EIS/EFIS can report. Yes, maybe an errant assumption on my part, but since I scoured the EIS install manual to no avail and I don't know enough on setting the EFIS Analog input parameters, I figured that the instructions Jeff provided were of a solution that would provide scaled output readings of the original values.

Again, I could be wrong... but l'll patiently await further guidance until I get a definitive "It can't be done". ;)
Bobturner
Posts: 429
Joined: Mon Mar 11, 2013 6:34 pm

Re: Electroair EI spark advance signal connection

Post by Bobturner »

Opps. My error. I meant to say that Jeff said that 0.01 volt (1 degree crankshaft revolution) could not be measured reliably, but I think you want 1 deg accuracy (not better than 1). Mechanics and engine companies seem to get upset if mag timing slips more than a degree or two. You may find that the efis is not accurate to 0.01 volt, but is repeatable to that accuracy. If true, you could calibrate the reading vs advance.
GRT_Jeff
Posts: 660
Joined: Tue Dec 11, 2012 12:11 am

Re: Electroair EI spark advance signal connection

Post by GRT_Jeff »

That is a very small voltage range so I don't know if it will be accurate or precise enough even on the EIS. The scaling is done in the software after the voltage has been sampled, so you're always limited to the fixed resolution of the analog-to-digital conversion hardware.

If you were using Aux 6 on the EIS, then
Set 6SF to 250 (this will scale to whole degrees)
Set 6OFF to 0

Set the 6th (last) D/I character to I for Integer. You have to cycle through all the combinations, leaving the others as they were.

Set the 6th (last) +/- character to + for Forward sensing. You have to cycle through all the combinations, leaving the others as they were.

In the EFIS, set the Aux6 Function to "Aux" and then you can set the name and set it as Integer.

To show tenths of a degree you would need an SF of 2500 and Decimal mode but I don't know if the EIS can even be set to that or if the converter has any more resolution.
Airdog
Posts: 17
Joined: Mon Jun 27, 2016 4:30 pm

Re: Electroair EI spark advance signal connection

Post by Airdog »

Jeff,

I'll give it a try when I install it all and see how it works. My Electroair controller will sit within 8 inches of the EIS4000 control head, so no real pain in the physical wiring. If it works, great. If not, we tried. Thanks for providing me the settings to try it out.

Bob - Understand what you're saying now. Yes, I'll try to keep my eye on the displayed reading vs the actual advance. I may even see if I can find one of the original meters and compare the two early on during flight testing.

Thanks gents, very informative. Regards.
Post Reply