MicroSquirt.com read only forum (Jan.15,2018)

Aaron Silidker wrote:Just did some tests with a resistor mounted in series.

With 0 ohms I was just under 22 volts p-p at 400 RPM
With 1m ohm I was just over 12 volts p-p at 400 RPM
With 10m ohms I was just over 2 volts p-p at 400 RPM

The only other thing connected to the VR besides one series resister is the oscilloscope.

Thoughts on the above numbers?

Question - with zero ohms (a direct short), you are still getting 22 volts at 400RPM? Is this a shunt resistor or a series resistor?

The test was to shunt the VR sensor to see the voltage output vs various loading - do not hook it up to the VR circuit, just take the VR+ and VR- leads from the sensor and hook across the shunt resistor. With this shunt you know the load being applied to the VR sensor, measuring the voltage across the resistor will yield the current flow. And you need to do this with an oscope and look at the peak voltage.

- Bruce

Bruce Bowling wrote:

Aaron Silidker wrote:Just did some tests with a resistor mounted in series.

With 0 ohms I was just under 22 volts p-p at 400 RPM
With 1m ohm I was just over 12 volts p-p at 400 RPM
With 10m ohms I was just over 2 volts p-p at 400 RPM

The only other thing connected to the VR besides one series resister is the oscilloscope.

Thoughts on the above numbers?

Question - with zero ohms (a direct short), you are still getting 22 volts at 400RPM? Is this a shunt resistor or a series resistor?

The test was to shunt the VR sensor to see the voltage output vs various loading - do not hook it up to the VR circuit, just take the VR+ and VR- leads from the sensor and hook across the shunt resistor. With this shunt you know the load being applied to the VR sensor, measuring the voltage across the resistor will yield the current flow. And you need to do this with an oscope and look at the peak voltage.

- Bruce

I did not have the uS hooked up to the VR circuit. When I measured voltage across the resistor hooked from VR+ to VR- leads, I got the same ~22 volts I had with no resistor. When I had the resistor hooked in series with the scope, I got the voltages I listed a few posts ago, much lower than 22 volts.

Tell me this bruce, do I have to worry about anything? At this point I have been thoroughly confused. I was under the impression from your sticky that the Gen 1 boards need to be modified in order to work with a high voltage signal like mine. I am also under the impression from you that I need to have a 10k resistor mounted in series with the uS. A 10k resistor produced an insignificant voltage drop as I measured today I had to go to mega ohms to see a difference.

Just tell me what I need to do please to make this work. Electrical engineering and me do not get along! I just really want the bike to run so I can have fun tuning it and riding my new EFI toy.

Aaron Silidker wrote: Tell me this bruce, do I have to worry about anything? At this point I have been thoroughly confused. I was under the impression from your sticky that the Gen 1 boards need to be modified in order to work with a high voltage signal like mine. I am also under the impression from you that I need to have a 10k resistor mounted in series with the uS. A 10k resistor produced an insignificant voltage drop as I measured today I had to go to mega ohms to see a difference.

Just tell me what I need to do please to make this work. Electrical engineering and me do not get along! I just really want the bike to run so I can have fun tuning it and riding my new EFI toy.

All you have to do is perform the diode change and put in the 10K resistor - thats all you need to do. Install on the engine and try it out.

All of this other stuff was academic - you indicated you wanted to understand more of what was going on, hence the extra testing.

- Bruce

Fair enough bruce!

I do want to understand it, but I get frustrated rather easily with this kind of thing. Mechanical makes far far far more sense to me. Understanding electrical stuff is a hassle and takes a ton of work/luck for me.