New Member Tom-student & Motor Signal Confusion

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New Member Tom-student & Motor Signal Confusion

Postby Tom-Student » Sun Jan 27, 2013 4:35 pm

Hi to everyone on here

I am a student using a Pico Scope as part of a final year project based on a FORD TDCI engine that is fixed to an engine dyno. I have very little understanding of automotive electronics at this stage and I plan to use this forum to help me improve my understanding of the signals that I get from the engine.

So far, my project supervisor has shown me how set up the scope in order to record the signals of the crankshaft position sensor and a few other sensors.

During the testing we recorded the motor signal which controls the variable vanes on the turbo, the signal we were expecting was a Pulse width modulation signal. However we recorded a signal which appears to be an on/off positive and negative pulse. The signal appears to be at a frequency of 50 Hz, we are slightly concerned that this could be due to some interference from the mains.

Has anyone recorded a variable vane motor signal with similar results?
If anyone is able to shed any light on this It would really help move my project forward to the next stage.

Many Thanks

Tom
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Re: New Member Tom-student & Motor Signal Confusion

Postby Wally » Mon Jan 28, 2013 10:00 am

Hi Tom, I think you will find it will be a lot easier if you can post a screen shot or better still the PSD file so we can all see exactly what is going on, not only with the trace but the settings you are using to get the trace.

Welcome to the forum.

Wally
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Re: New Member Tom-student & Motor Signal Confusion

Postby Tom-Student » Mon Jan 28, 2013 12:17 pm

Hi Wally

Thank you for your reply

The file should be attached to this post

The probes were connected to the variable vane actuator for the turbo using the +ive and -ive connections. During the test, the engine speed was in a steady state causing no movement of the variable vanes. Manual force was applied to the actuator in order for a signal to counteract this action to be generated. This is what caused the signal that is shown in the file.

As for the settings, I'm not sure what you mean? I thought they are shown in the file, are you talking about the settings of the software?

Many Thanks

Tom
Attachments
motor signal with fiddling 20130124-0001.psdata
Vane actuator signal
(581.79 KiB) Downloaded 353 times
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Re: New Member Tom-student & Motor Signal Confusion

Postby Robski » Mon Jan 28, 2013 6:26 pm

Oh dear..........

Am i reading right that you are using -VE for ground at the actual actuator ?

Ground at the Batt - & probe the actuator -VE with the red probe & if you want to see the supply side deploy another channel.

I take it you're trying to see the PWM command ??
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Re: New Member Tom-student & Motor Signal Confusion

Postby Tom-Student » Thu Jan 31, 2013 12:56 pm

We were using the two wires attached to the motor to compare the voltage relative to each other.

Yes we were expecting to see a PWM command, that was based on my research that most automotive companies seem to be using PWM to control variable vane turbo motors .

Can anybody confirm whether the FORD tdci engine uses PWM for this? or whether my attached file to the previous post is an incorrect reading of the signal?

Many thanks

Tom
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