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Help with building your Speeduino, installing it, getting it to run etc.
By scartail
Hi all...

Will a GM HEI 4-pin ignition module work with Speeduino? I see only 7 and 8 pin modules listed in the hardware requirement section.

I am attempting to do this upgrade swap... https://www.zdriver.com/forums/240z-280 ... hei-27569/


When I connect everything, and connect the signal wire to IGN1 output, the IGN1 led on the board (once flashing) goes solid red. I measure 8v as out of the module. And before connecting the signal wire, I get a frequency of 25 hz, and after it jumps to 120 hz. I'm currently running everything on the bench, and I did not have spark when I connect everything.

Anyone advise? Thanks in advance.
before connecting
Screenshot_20200208-185630.jpg (525.37 KiB) Viewed 5578 times
after connecting
Screenshot_20200208-185641.jpg (641.58 KiB) Viewed 5578 times
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Don't forget the primary module ground is through the module mounting bolt grommets. Your diagram does not show that. The Speeduino IGN channels are push-pull, so they switch from full voltage (5V or 12V selected by jumper) to full ground. I would use 5V setting for this signal.

Using GM HEI 4-pin as basic coil driver
GM_4-pin_coil_driver.png (15.02 KiB) Viewed 5503 times
By scartail
thanks for the feedback guys.

@PSI, would you elaborate on "push-pull"? I had the jumper set to 12v. Is there something else I must change? And I think you're right about the ground. I'll double check.
By scartail

Here's a follow-up, in case anyone else goes through this process. I haven't wrapped my head around why it worked out this way, but it's a step forward, I think.

I went through and check my connections again, once I changed the ground to the correct post, something different happened. When I connected the signal wire, the ign led would go off (previously flashing). I then took a step back and connect the R and W to the dizzy, instead of the speeduino. I confirmed that I got spark, and things were running as expected. I figure it could hurt (or may it could have) that I put the signal wire to the W post (instead of what was shown in PSI's post).

BTW: I didnt know there were many types of 4-pin GM HEI modules. I measured mine, and it is a 0v type.

thanks for all the help!
IMG_20200210_133034.jpg (3.58 MiB) Viewed 5474 times
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scartail wrote:
Mon Feb 10, 2020 3:41 pm
@PSI, would you elaborate on "push-pull"?
The ignition outputs from Speeduino use ICs with two transistors per channel. One transistor switches voltage ON (high) and when that turns off, the other one switches from off to ground. So, you don't just get HIGH and OFF, or GND and OFF, but both HIGH and GND alternately. This makes for much quicker and complete "hard" switching of ignition coil drivers. it also means you can trigger stuff that requires either HIGH or GND. The GM 4-pin requires a HIGH to trigger the coil into dwell, and fires the coil "going low".
scartail wrote:
Mon Feb 10, 2020 7:11 pm
I figure it could hurt (or may it could have) that I put the signal wire to the W post (instead of what was shown in PSI's post).
What's happening there, is that the W terminal is connected internally to the G terminal through three high-ohm resistors. Only G triggers the module, with a high G signal switching the coil on terminal C to ground through the mounting bolt. W is designed to produce an increasing bias voltage to the VR sensor (you're not using) that prevents coil lock-up or constant dwell and ignition shutdown at high-rpm (in the original use).

So, when you disconnect G and signal to W, it is going through the resistors internally to G and triggering it. It should work as-intended if you just send the IGN signal to G.
scartail wrote:
Mon Feb 10, 2020 7:11 pm
BTW: I didnt know there were many types of 4-pin GM HEI modules. I measured mine, and it is a 0v type.
That is true, and they should all work the same in the original application and use. However, for stuff like this, little differences can cause weird results. You may find that your version works when you leave W disconnected instead of grounding it. Find your combination and do your thing!

GM HEI 4-pin internal diagram
mc3334_blockdiag_GM_4-pin.jpg (46.53 KiB) Viewed 5453 times
By scartail
Good info David! I'll see what happens if I ground out the G pin. I don't want to mess with it too much, as it seems to do what I want it to do. Do you think if I change the ign output "high", it would work as originally intended?

This guy reiterates your view on the possible issues when using the 0v family modules outside intended use. Apparently, the 0v style modules are non-mc3334.
http://gpzweb.s3-website-us-east-1.amaz ... dules.html
By scartail
Torslund wrote:I took one HEI and put it in a contact breaker car, I put a transistor on input and inverted the breaker signal :) Runs fine.
That's good to know. So the transistor converted the waveform, and the inverter flip the signal? Were you putting the signal on the G port?

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