Tach Signal Problems
11-12-2016, 05:30 PM
#1
Tach Signal Problems
I'm running an MS2extra/PCB3 with the TPI adaptor board (all mounted in a GM ECM case), and built an arduino run progressive shift light ( https://github.com/chippernut/ShiftLightV2_1 ) that I'm trying to get working. I'm also using a Crane HI-6 ignition box with their harness to plug it in to the factory '165 harness.
For this testing have the activation rpm (when the LED's start incrementing) set to 1000rpm and the shift rpm (when they all light up and flash) to 3000 for testing to confirm operation without annoying the neighbors/attracting the cops.
I wanted to connect it straight to the MS since that makes all the wiring under 2' long and not having to run any wiring outside of the passenger compartment- the MS is getting a good rpm signal as per the datalogs. Originally I tried connecting it straight to the original harness (pin D4/white wire in the o '165 harness) and the shift light was flaky- It seemed to be getting an rpm signal but once or twice a second it would flash like the rpm was spiking and even going past the shift point. Otherwise the engine ran fine. I tried all the conditioning and trigger settings with no luck.
I gave in and ran the same wire out the window and under the hood to the tach output on the Crane Hi-6. This way I got a perfect signal to the shift light, it worked exactly right, but it broke other stuff:
Anyone have any idea what pin/how to connect it to the MS/TPI adaptor, why it isn't working or why using the tach output on the Hi-6 is messing up the engine and the dash?
Here's a video of it connected to the Hi-6 tach connection, where you can see it working, the messed up dash and you can sort of hear it popping when I rev it to set of the shift flashing:
Here's a video of me playing with it on a bench, at the end you can see the plate that I machined to mount the LEDs to the face of the dash over the steering column (ignore the sound, it's my sick 4y/o arguing with her mother):
For this testing have the activation rpm (when the LED's start incrementing) set to 1000rpm and the shift rpm (when they all light up and flash) to 3000 for testing to confirm operation without annoying the neighbors/attracting the cops.
I wanted to connect it straight to the MS since that makes all the wiring under 2' long and not having to run any wiring outside of the passenger compartment- the MS is getting a good rpm signal as per the datalogs. Originally I tried connecting it straight to the original harness (pin D4/white wire in the o '165 harness) and the shift light was flaky- It seemed to be getting an rpm signal but once or twice a second it would flash like the rpm was spiking and even going past the shift point. Otherwise the engine ran fine. I tried all the conditioning and trigger settings with no luck.
I gave in and ran the same wire out the window and under the hood to the tach output on the Crane Hi-6. This way I got a perfect signal to the shift light, it worked exactly right, but it broke other stuff:
- The tach in the dash stopped working correctly- at idle it showed 500rpm, revving it at all made it go instantly to 3500rpm and stick there and the shift light stuck on
- The engine is acting like the timing is all messed up, it's sluggish, doesn't want to rev, and trying to rev it to 3000 to set off the shift flash caused it to pop and rev funny. I didn't see anything in the datalogs and I haven't had time to check if the timing is off with a timing light.
Anyone have any idea what pin/how to connect it to the MS/TPI adaptor, why it isn't working or why using the tach output on the Hi-6 is messing up the engine and the dash?
Here's a video of it connected to the Hi-6 tach connection, where you can see it working, the messed up dash and you can sort of hear it popping when I rev it to set of the shift flashing:
Here's a video of me playing with it on a bench, at the end you can see the plate that I machined to mount the LEDs to the face of the dash over the steering column (ignore the sound, it's my sick 4y/o arguing with her mother):
11-12-2016, 06:37 PM
#2
Re: Tach Signal Problems
Schematics for the shiftlight?
I built a speedometer for my car based on Arduino, and had an issue initially with the speed jumping around, especially when the engine was revved. I traced it down to small voltage spikes on the power input that were also effected by EMI based on where the I sat the speedo in the car.
The solution ended up being adding a low pass filter to the power input.
I built a speedometer for my car based on Arduino, and had an issue initially with the speed jumping around, especially when the engine was revved. I traced it down to small voltage spikes on the power input that were also effected by EMI based on where the I sat the speedo in the car.
The solution ended up being adding a low pass filter to the power input.
11-13-2016, 04:02 PM
#3
Re: Tach Signal Problems
Schematics for the shiftlight?
I built a speedometer for my car based on Arduino, and had an issue initially with the speed jumping around, especially when the engine was revved. I traced it down to small voltage spikes on the power input that were also effected by EMI based on where the I sat the speedo in the car.
The solution ended up being adding a low pass filter to the power input.
I built a speedometer for my car based on Arduino, and had an issue initially with the speed jumping around, especially when the engine was revved. I traced it down to small voltage spikes on the power input that were also effected by EMI based on where the I sat the speedo in the car.
The solution ended up being adding a low pass filter to the power input.
11-13-2016, 05:46 PM
#4
Re: Tach Signal Problems
Two things I see missing from the schematic:
A decoupling capacitor on the tach input and a lack of filtering on the power input.
If you add both, you should see no more spikes on the RPM input and will also show less effect on any devices connected to it.
The lack of decoupling capacitor is likely what is causing the engine to run rough when you connect this circuit to the HI-6.
A decoupling capacitor on the tach input and a lack of filtering on the power input.
If you add both, you should see no more spikes on the RPM input and will also show less effect on any devices connected to it.
The lack of decoupling capacitor is likely what is causing the engine to run rough when you connect this circuit to the HI-6.
11-16-2016, 01:12 AM
#5
Re: Tach Signal Problems
Before I saw your last response I had the thought that if the shift light is working correctly when connected to the tach output on the ignition box but the spark advance and tach seen to be messed up maybe it's feeding some sort of signal back into the ignition box that is messing stuff up, so on that premise I stuck a small diode in the line, negative side towards the shift light. That mostly fixed things. The spark advance/engine seems to be running fine and the tach works now.
The reason I say "mostly" is that I guess I'm not positive that it's not still affecting the ignition box and that also appears to have induced some noise in the signal. Now on about a 15 minute drive I get about 3-5 "shift" flashes from the shift light when it's at idle or close to it.
Decoupling capacitor? Like what value and wired how?
Filtering on the power input, like a capacitor across the power input or something else?
(I'm fairly crappy at electronics, I know just enough to cause myself trouble, though I'm pretty good at building stuff)
The reason I say "mostly" is that I guess I'm not positive that it's not still affecting the ignition box and that also appears to have induced some noise in the signal. Now on about a 15 minute drive I get about 3-5 "shift" flashes from the shift light when it's at idle or close to it.
Two things I see missing from the schematic:
A decoupling capacitor on the tach input and a lack of filtering on the power input.
If you add both, you should see no more spikes on the RPM input and will also show less effect on any devices connected to it.
The lack of decoupling capacitor is likely what is causing the engine to run rough when you connect this circuit to the HI-6.
A decoupling capacitor on the tach input and a lack of filtering on the power input.
If you add both, you should see no more spikes on the RPM input and will also show less effect on any devices connected to it.
The lack of decoupling capacitor is likely what is causing the engine to run rough when you connect this circuit to the HI-6.
Filtering on the power input, like a capacitor across the power input or something else?
(I'm fairly crappy at electronics, I know just enough to cause myself trouble, though I'm pretty good at building stuff)
