Microsquirt - incorrect spark output/configuration

[Kclement19]

Update: I failed one hall effect sensor for crank trigger (it actually melted down), and now I believe I have failed a second (inconsistent output). The engine is being run on a test stand and has less than 4 hrs of run time total. I'm concerned that I could have damaged the circuity of the microsquirt by how I had the hall effect sensor connected. I’m also wondering if my incorrect connections and could have damaged both hall sensors and there is no problem with the microsquirt (preferred option). Below is a summary of events regarding connections of my hall effect sensors:

1) Sensor #1, connection #1
The first time I had the hall effect sensor hooked up, I used the following connections per recommendations from someone who is helping me with my install and has installed similar setups:
-HALL Blue signal wire to OPTOIN-
-HALL Red power wire to +12v (7.5 AMP fuse - common supply to LC-2 O2 sensor controller)
-HALL Black ground wire to SENSOR GROUND
-OPTOIN+ floating/not connected
With the above connections, I was unable to get an RPM signal.

2) Sensor #1, connection #2
At that point, I started reading manuals online (B&G not knowing that I actually am running MSextra) and decided that hooking OPTOIN+ to +12v would be a good idea. It was hooked up this way:
-HALL Blue signal wire to OPTOIN-
-HALL Red power wire to +12v (7.5 AMP fuse - common supply to LC-2 O2 sensor controller)
-HALL Black ground wire to SENSOR GROUND
-OPTOIN+ connected to +12v (2 AMP fuse - common supply to microsquirt +12v)
This way, I was able to get a trigger signal, but engine did not run with microsquirt controlling spark. I ended up turning OFF "Tach Period Rejection" and my trigger logs looked better and was able to get engine to run with microsquirt controlling spark. Shortly after, I lost signal from my hall sensor and found that it was no longer lighting up when the magnet passed it. I put another magnet close to it and it the light came on but stayed on after the magnet was removed and then spit molten plastic out of itself.

3) Sensor #2, connection #2
I ordered another hall sensor and planned to hook it up using VR inputs instead of OPTO based on MSextra manual, but I forgot to change the inputs before powering up the sensor for the first time. Connections were same as #2:
-HALL Blue signal wire to OPTOIN-
-HALL Red power wire to +12v (7.5 AMP fuse - common supply to LC-2 O2 sensor controller)
-HALL Black ground wire to SENSOR GROUND
-OPTOIN+ connected to +12v (2 AMP fuse - common supply to microsquirt +12v)
The sensor worked again, but I don't recall running the engine this time.

4) Sensor #2, connection #3
After getting the sensor to work, I decided that I should switch to VR input per MSextra manual:
-OPTOIN+, OPTOIN- not connected/floating
-VR1+ not connected/floating
-HALL Blue signal wire to VR1-
-HALL Red power wire to +12v (7.5 AMP fuse - common supply to LC-2 O2 sensor controller)
-HALL Black ground wire to SENSOR GROUND
The trigger logs looked good this way as long as "Tach Period Rejection" was OFF. The engine ran good again. No issues....A few days later, I tried to start the engine and I have lost RPM signal again. The LED light on the HALL effect is not blinking on and off consistently when the magnet passes it. Sometimes the light is dimly lit, some times the light flickers when the crankshaft is stationary. And most importantly, its output signal is inconsistent in the trigger log. It appears I have damaged another Hall effect sensor, but I'm not sure why.

Here are voltage measurements with microsquirt powered up, hall effect sensor disconnected, wires only connected to microsquirt (hall not connected)
-VR1- measures 2.36 VDC
-VR1+ measures 2.38 VDC
-VR2- measures 2.36 VDC
-VR2+ measures 2.38 VDC
-OPTOIN- measures ~0.02 VDC
-OPTOIN+ measures ~0.001 VDC

Here are voltage measurements with microsquirt powered up, hall effect sensor connected per “connection #3, magnet in the presence of the hall (VR1- to ground).
-VR1- measures 0.07 VDC
-VR1+ measures 1.29 VDC
-VR2- measures 2.36 VDC
-VR2+ measures 2.38 VDC
-OPTOIN- measures ~0.02 VDC
-OPTOIN+ measures ~0.001 VDC

Questions:
-Could I have damaged the microsquirt by applying +12v to OPTOIN+ (fused at 2A)?
-OR am I simply damaging my hall sensors by having it connected per “connection #2”? The second hall sensor was connected per connection #2 for a short duration.
-What voltage would you expect at the VR1-/+, VR2-/+, OPTOIN-/+ when powering up the microsquirt without any connections to these wires? I was surprised to find something other than zero volts here.
-If it should be ~0 volts on these wires, could I be backfeeding currentl through my hall sensor though its signal wire via voltage from VR1-?

I’m thinking about replacing the hall sensor one more time without every connecting per “connection #2” and only running it with “connection #3” to see if it fails again or not.

Thoughts?

[jsmcortina]

Connection #1 wasn't going to work. When using the Opto input you have to connect both OPTO+ and OPTO- to something - as you did with connection #2.

The small current draw of the OPTO isolator is VERY unlikely to damage the hall sensor.

What seems more likely perhaps is that you have a noisy 12V that is spiking above the maximum allowed voltage for the sensor. As a test you could perhaps try running that sensor off its own 9V battery. (e.g. PP9) and see if it works ok then.

James

[Kclement19]

Connection #1 wasn't going to work. When using the Opto input you have to connect both OPTO+ and OPTO- to something - as you did with connection #2.

The small current draw of the OPTO isolator is VERY unlikely to damage the hall sensor.

What seems more likely perhaps is that you have a noisy 12V that is spiking above the maximum allowed voltage for the sensor. As a test you could perhaps try running that sensor off its own 9V battery. (e.g. PP9) and see if it works ok then.

James

Thank you James. Do you think I could've damaged the OPTO/VR circuits by connecting a +12v feed to OPTO+ allowing more current to flow through the mircosquirt/hall sensor? Also, do you expect voltage greater than zero at the VR wires? As mentioned above, i see ~2.4 volts at VR-1 -/+ and VR-2 -/+ without sensors connected and with the microsquirt powered up?

Thanks,
Kelly

[jsmcortina]

Thank you James. Do you think I could've damaged the OPTO/VR circuits by connecting a +12v feed to OPTO+ allowing more current to flow through the mircosquirt/hall sensor?

No because that is a normal way to connect the OPTO+.

Also, do you expect voltage greater than zero at the VR wires? As mentioned above, i see ~2.4 volts at VR-1 -/+ and VR-2 -/+ without sensors connected and with the microsquirt powered up?

Yes, that's normal.

James