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Electronic Ignition spark advance signal boost

 
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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Sat Dec 16, 2017 10:11 am    Post subject: Electronic Ignition spark advance signal boost Reply with quote

Hi All,

I have yet another issue I was hoping the gurus here on the list could help me figure out.

I have an Electroair electronic ignition system that has a wire coming out of the unit's controller for a spark advance meter. Electroair (nor their customers apparently) hasn't used this wire or a meter in ages, so it's a rather dormant feature, although it does still put out an active (albeit optional) signal to show the set spark advance BTDC.

I would like to attach this Electroair spark advance wire to an Auxiliary port on my GRT EIS4000 engine management system to then show the spark advance on my EFIS. However, the issue I'm running into is the spark advance signal output, the voltage range of which may prove too low for the GRT EIS to read reliably (as per GRT).

The Electroair spark advance signal voltage output is from 0.00V to 0.40V, and is scaled 0.01 volt per every degree of advance. So just to be clear:
0.01V = 1 degree of advance
0.10V = 10 degrees of advance
0.28V = 28 degrees of advance

What I would like to achieve is to amplify the spark advance signal voltage x 10 so that the GRT could see every 0.1V as 1 degree of spark advance, so again for clarity:
0.1V = 1 degree of advance
1.0V = 10 degrees of advance
2.8V = 28 degrees of advance

Since the original spark advance signal is on a range of 0 to 0.4 volts, if I amped it up x10 then my max output would be 4.0 volts, still well under the 5.0V max input of the GRT EIS auxiliary ports.

Regards,
Wade


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PostPosted: Sat Dec 16, 2017 7:06 pm    Post subject: Electronic Ignition spark advance signal boost Reply with quote

Wade
If you google "non inverting op amp" you should find a simple voltage
multiplier circuit that you can power with the EIS 5 volt sensor supply.
Pretty much any 8 pin op amp and a couple of resistors to set the gain
at 10 will do this nicely.
Ken

On 16/12/2017 1:11 PM, Airdog77 wrote:
Quote:


Hi All,

I have yet another issue I was hoping the gurus here on the list could help me figure out.

I have an Electroair electronic ignition system that has a wire coming out of the unit's controller for a spark advance meter. Electroair (nor their customers apparently) hasn't used this wire or a meter in ages, so it's a rather dormant feature, although it does still put out an active (albeit optional) signal to show the set spark advance BTDC.

I would like to attach this Electroair spark advance wire to an Auxiliary port on my GRT EIS4000 engine management system to then show the spark advance on my EFIS. However, the issue I'm running into is the spark advance signal output, the voltage range of which may prove too low for the GRT EIS to read reliably (as per GRT).

The Electroair spark advance signal voltage output is from 0.00V to 0.40V, and is scaled 0.01 volt per every degree of advance. So just to be clear:
0.01V = 1 degree of advance
0.10V = 10 degrees of advance
0.28V = 28 degrees of advance

What I would like to achieve is to amplify the spark advance signal voltage x 10 so that the GRT could see every 0.1V as 1 degree of spark advance, so again for clarity:
0.1V = 1 degree of advance
1.0V = 10 degrees of advance
2.8V = 28 degrees of advance

Since the original spark advance signal is on a range of 0 to 0.4 volts, if I amped it up x10 then my max output would be 4.0 volts, still well under the 5.0V max input of the GRT EIS auxiliary ports.

Regards,
Wade

--------
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com


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http://forums.matronics.com/viewtopic.php?p=476445#476445




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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Sat Dec 16, 2017 8:32 pm    Post subject: Re: Electronic Ignition spark advance signal boost Reply with quote

Ken,

Awesome. I'll check it out.

Thanks!
Wade


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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Sun Dec 17, 2017 7:28 am    Post subject: Re: Electronic Ignition spark advance signal boost Reply with quote

Ken,

I think I've got the function of the non inverting op amp down.... pretty cool. Just a couple of questions before I pull the trigger on purchasing any.

I noticed on Mouser that the input voltage is usually 1.8, 2.7 or 4.5 volts. Am I reading this right that those are +/- input volt, so say -1.8V to +1.8V. May seem like a silly question, but just asking since I need 0V or 0.01 volts covered as a possible input voltage.

Also, I think I've got it right that the R1 and R2 resistors values are set simply as a ratio to provide the correct gain. Are the resistor values completely arbitrary, or any standards that I should be following? Right now I have R2 = 500 Ohm, R1 = 4.5K Ohm.

Again, thanks for the info on these op amps. Neat stuff.

Cheers,
Wade


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PostPosted: Mon Dec 18, 2017 9:38 am    Post subject: Electronic Ignition spark advance signal boost Reply with quote

On Mon, Dec 18, 2017 at 11:10 AM, Airdog77 <Airdog77(at)gmail.com (Airdog77(at)gmail.com)> wrote:
Quote:
--> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)gmail.com (Airdog77(at)gmail.com)>

Ken, I would think these things (at least a version out there) would go down to 0.0 volts... Roger on using a higher resistor value.

Charlie, I think you're saying simply supply 12V power to the op amp (one rated for 12V) at the V+ and V- pins?  Spark advance input is obviously unchanged (at +In).  I guess the affect on the output being more linear is internal to the op amp?

Regards,
Wade

--------
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com

My comment was based on using one of the ancient op amp circuits, most of which get a bit nonlinear when output approaches the supply rail voltage. The much more modern instrumentation amp that Bob referenced doesn't seem to have that issue, making it simple to power it from the EFIS's 5V source.


On Bob's comment about ground references: I'm not up to speed on that device, but I'd expect a differential amplifier to look at the voltage difference between the two source voltages, and in this case, the <-> input would be the ground reference at the device you're measuring. Since it's a differential amplifier, I'd expect it to be immune to ground reference issues, but hey; you don't know until you test. 
If I were setting it up, I'd start by hooking the <+> input to the advance output, the <-> input to the ground terminal *on the  ignition module*. I'd supply power from the EFIS & ground from the same spot the EFIS gets its ground. I wasn't sure what Bob meant in his previous post, either, but he may have been saying to supply ground from the ignition module; the same point that supplies 'reference' to the <-> input. (By 'ground', I'm talking about the power supply ground terminal; not the <-> input to the amp.)


Quote:
 


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Airdog77



Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

PostPosted: Mon Dec 18, 2017 10:05 am    Post subject: Re: Electronic Ignition spark advance signal boost Reply with quote

Charlie,

Yes. Tracking. When I checked the Electroair manual, interestingly enough the only ground available on that unit is the ignition module ground (vs the controller unit).... since I was scrounging around to find a ground to use for -In on the AD626 that Bob recommended.

Cheers,
Wade


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Eric Page



Joined: 15 Feb 2017
Posts: 241

PostPosted: Mon Dec 18, 2017 11:03 am    Post subject: Re: Electronic Ignition spark advance signal boost Reply with quote

Yes, I believe Bob meant to ground both signal and supply at the ignition module. The op-amp won't know if there's a few mV ground potential difference on the supply side; just the signal side. So, grounding the supply at the ignition module instead of at the EIS won't affect operation, but it *will* give the op-amp a good reference for the advance signal.

Wade, which model of the GRT EIS are you using? If it's the 4000, there appears to be a "4.8V Exitation Output" on pin 25. The AD626 will draw a small fraction of a milliamp, so it should be safe to use this pin to power the circuit.

Eric


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