Fun on the oscilloscope - comparing J105s and J109s (lots of pics)
 

I did this to answer one question: Are J105s and J109s functionally equivalent? The answer to that question is yes, they do the same thing! :lol: More importantly though, wired up the same they can be interchangable. I present these plots for those wishing to draw further conclusions. First, a note on my test setup.

My function generator:

https://www.rx7club.com/attachment.p...1&d=1185092697

:rlaugh:
That there is an FB distributor. I did this to get a true to life input signal. The drill has a maximum RPM of 1000 which would correspond to an engine RPM of 2000 - high speed analysis was not possible with this setup. All the tests were not done at the same speed. If you wish to calculate the RPM of any plot keep in mind that the reluctor has four lobes, so there will be 2 pulses per engine rotation.

All tests were done with time on the abscissa and voltage on the ordinate. In the pickup test, the input signal was + and the ground was -. In all ignitor tests the input signal to the oscilloscope was read from the C terminal of the ignitor and the ground reference was +12.05V. When two ignitors were compared on the same plot they were wired to the same pickup - this is important particularly in the J105 vs J109 plot, as the B to - resistance in a J109 is 51kOhm, whereas the B to - resistance in a J105 is 20kOhm. Finally, in the ignitor vs pickup plots, the + wire of the pickup was plotted with a ground of +12.05V.

Ok, on to the plots.

The first one is the pickup signal at low speed, 1.8V/div, 10ms/div
The shadow image of the plot is due to the camera

https://www.rx7club.com/attachment.p...1&d=1185095145


Next, the pickup signal again, 2.0V/div, 5ms/div
This one is clearer

https://www.rx7club.com/attachment.p...1&d=1185095145


J109 (top), J105 (bottom) 5.0V/div, 1.5ms/div
This is why you should never mix the two for DLFDIS, at least not off the same pickup

https://www.rx7club.com/attachment.p...1&d=1185095145


4th plot - this one's a little wide so click below to see it
J109 directly superimosed over J105, 5.0V/div, 6ms/div
It's a little difficult to see, but this one shows a slight difference in slope, at least when they're wired together.

Another plot that I made, though I'm not going to waste the bandwidth to show it, is of the J105's bias. In the presence of power and in the absence of an input signal, the J105 will output 12V at it's C terminal whereas the J109 outputs 0V.

more plots to follow

moving right along

The first one here isn't much different from the one above with a J109 and J105 on the same graph, but it was taken at the same frequency as the above plot and in this one you can determine just what that frequency was.
J109 (top), j105 (bottom) 5.0V/div, 2ms/div

https://www.rx7club.com/attachment.p...1&d=1185129843


Just to make sure that this difference in the plots when a J109 was wired alongside a J105 wasn't due to a problem with the ignitors I was using, I repeated the test with other ignitors. Here're a couple of those tests.

J109#2 (top), j105#1 (bottom) 5.0V/div, 1.5ms/div

https://www.rx7club.com/attachment.p...1&d=1185129843


J109#1 (top), j105#2 (bottom) 5.0V/div, 1.5ms/div

https://www.rx7club.com/attachment.p...1&d=1185129843

Last plots.

Here are a series of the ignitors plotted against the pickup signal.


J109 @5.0V/div vs inductor @2.0V/div, 3.5ms/div

https://www.rx7club.com/attachment.p...1&d=1185130425


J109 @5.0V/div vs inductor @2.0V/div, 1.5ms/div

https://www.rx7club.com/attachment.p...1&d=1185130425


J105 @5.0V/div vs inductor @2.0V/div, 1.8ms/div

https://www.rx7club.com/attachment.p...1&d=1185130425


J105 @5.0V/div vs inductor @2.0V/div, 0.9ms/div

https://www.rx7club.com/attachment.p...1&d=1185130425

excellent!!!

The plot for the pickup is almost precisely how I imagined it would look! It's basically lopsided AC with a slow rise time and a quick drop off.

interesting stuff :bigthumb:

wow thats neat.

This is archive material.

I think floyd used that in '76