I have a buddy with an aftermarket Accel HEI dizzy (no instructions). Which terminal is the 5V square wave? Is it the Tach terminal, or is that the VR signal?
CK5
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Who Here is an HEI Expert?
- Thread starter BGKYK5
- Start date
trailblazr81
1/2 ton status
Have you tried looking at Accel's websight? They have instruction books online.
http://www.accel-ignition.com/InstructionSheetsList.aspx?BrandID=3
http://www.accel-ignition.com/InstructionSheetsList.aspx?BrandID=3
I did try that, but everything I saw just told me to plug in the connector. We are trying to do something a little wierd, so we aren't doing a plug and play install. Now I am thinking we want the "C-" terminal, but I'm still not sure.
Pvt. Maggot
1/2 ton status
What exactly is it that your trying to do?
broncoman6524
1/2 ton status
For an accel dist, from the hei ones that i have seen they have a 4pin module.
This means that it is the simplest (5 and 7 pins have extra bs for computers and knock sensors), To make it work you will need 12volts going into the dist (coil) This is the white connector on the trucks harness.
Then connect the 3wire from dist ito the cap, and connect your tach wire into the remainin socket in the cap.
The -C terminal is the secondary ground for the coil, the neg coming off ofthe pickup coil through the module, then into that connector, and then to the coil.
This means that it is the simplest (5 and 7 pins have extra bs for computers and knock sensors), To make it work you will need 12volts going into the dist (coil) This is the white connector on the trucks harness.
Then connect the 3wire from dist ito the cap, and connect your tach wire into the remainin socket in the cap.
The -C terminal is the secondary ground for the coil, the neg coming off ofthe pickup coil through the module, then into that connector, and then to the coil.
Anybody know what that Tach signal is? Is it a straight VR or Hall Effect signal (varying amplitude sine wave) or is it a 5V or 12V square wave?
Why not make everyones life easier and let us know what you're trying to do and then maybe we can help you.
readymix
3/4 ton status
BGKYK5 said:
Is there any other kind of sine wave
Haha, OK a varying peak amplitude sine wave, as in the peak amplitude increases with engine speed.
Well, we are trying to hook up a data acquisition system to measure and record engine speed (among other things). We need to hook up to the square wave signal to get it to work (the VR signal is too big at higher engine speeds - it will kill our equipment). Any data scrapers in da house?
Well, we are trying to hook up a data acquisition system to measure and record engine speed (among other things). We need to hook up to the square wave signal to get it to work (the VR signal is too big at higher engine speeds - it will kill our equipment). Any data scrapers in da house?
If you're too lazy to search for the answer, then I'm too lazy to find a diagram.
Here's the best description I can give you from memory:
The VR signal comes from the pickup coil in the center of the dizzy. That plugs into the module internally, so that signal is not available outside, unless you have a computer controlled version (i.e. 7-pin) or an ESC module (i.e. 5-pin). The other end of the module is the power in/out side and it plugs into the distributor cap. This is the connector closer to the body of the cap. It is a 3 pin with Power, GND and coil drive being rear, center and front, respectively. Further from the cap body are the connectors for 12V and tach. Tach is the same thing as the coil drive. It is normally pulled high (connected to 12V through the coil), but it is pulled low for a few ms at a time (by the module) to charge the coil. When this signal is transitioning from low to high the spark occurs.
If you're looking for a 50% duty clean square wave to time something with, you are thinking of another type of ignition system.
Here's the best description I can give you from memory:
The VR signal comes from the pickup coil in the center of the dizzy. That plugs into the module internally, so that signal is not available outside, unless you have a computer controlled version (i.e. 7-pin) or an ESC module (i.e. 5-pin). The other end of the module is the power in/out side and it plugs into the distributor cap. This is the connector closer to the body of the cap. It is a 3 pin with Power, GND and coil drive being rear, center and front, respectively. Further from the cap body are the connectors for 12V and tach. Tach is the same thing as the coil drive. It is normally pulled high (connected to 12V through the coil), but it is pulled low for a few ms at a time (by the module) to charge the coil. When this signal is transitioning from low to high the spark occurs.
If you're looking for a 50% duty clean square wave to time something with, you are thinking of another type of ignition system.
What kind of interface does the data acq. have? You should be able to use the tach signal for this, but you might need a diode circuit in the interface to clip the transients off. It has to be fast enough to catch dwell times down to 2 ms. and capture about 370 events per second. Don't forget to divide by 8.
Thanks for the info. I've found lot's of diagrams - none of them useful (they tell you the name of the signal, but no details on what the signal is). We were hooked to Tach, but it killed a DAQ module (which was good to 30V). I was going to scope it, but didn't want to kill the scope too. I was thinking that the tach must be a direct VR signal, but if it is a 12V square wave we should be fine. Something else must have killed it. We count pulses on the low/high transition and 2ms is not a problem. And actually to go from Hz to RPM you multiply by 15 (for 8 cyl w/o waste spark).
Yes, the signal is not really a "square wave" because the ignition coil has so much inductance. This is why you need an interface circuit to protect the data acq. I have had a scope on the coil drive (i.e. Tach terminal) many times. Just use a 10X or 100X probe and make sure the vertical range is OK. In fact, this is the best way for you to see exactly what signal you are trying to measure.
I apologize for the divide by 8. You can see by my "events per second" info that I had already calculated the conversion (~5550rpm). Divide by 4 (8 cylinders/2-stroke) and multiply by 60 (seconds/minute) would been the right info.
I apologize for the divide by 8. You can see by my "events per second" info that I had already calculated the conversion (~5550rpm). Divide by 4 (8 cylinders/2-stroke) and multiply by 60 (seconds/minute) would been the right info.
readymix
3/4 ton status
Blue85 said:
Nope never heard of it
Please.........do explain how you could have a sine wave that doen not vary in amplitude.
I guess you are describing everything in terms of DC. A 1kHz 1Vrms sine wave is a rising and falling signal, but it has a constant amplitude of 1Vrms, by definition.
The comments further back about changing amplitude of the VR signal are correct. As engine speed changes, that signal changes in both frequency and amplitude. This is different from the FM radio example because that varies only in frequency. The two types of "variation" are different.
The comments further back about changing amplitude of the VR signal are correct. As engine speed changes, that signal changes in both frequency and amplitude. This is different from the FM radio example because that varies only in frequency. The two types of "variation" are different.
Well I wussed out and punted. We dug up an old MSD 6A box and used that just to convert the VR tach signal into a 12V square wave.
readymix
3/4 ton status
readymix said:
Quoted myself
