DSM CAS Signal DAQ Measurement

[jsdevel]

I hooked my DSM CAS up to my MicroDAQ to test it's signal. I used analog inputs on the DAQ with the Crank and Cam inputs. The CAS was powered by a 2 AMP power supply.

Here is what the signal looked like:

dsm-cas-daq.png

I kept the speed constant with a drill.

To me it doesn't look very good. It is possible that I didn't acquire the signal properly. Would this signal be digital?

Update 03/28/2017

You can see it working properly at the end of this post http://www.msextra.com/forums/viewtopic ... 24#p498224

[jsmcortina]

Sounds like you missed out the necessary pullup resistors.

James

[jsdevel]

Doh! I certainly did. I hooked the crank/cam output wires directly to the DAQ. Would a resistor in parallel to ground keep the signal from floating? Do you have a circuit I could follow?

[prof315]

check the hardware manual about open collector hall /optical sensors and pull ups

[jsdevel]

I gather that I'll need to replicate the transistor/resistor circuit from 5.2.4 on a breadboard then?

[jsmcortina]

. Would a resistor in parallel to ground keep the signal from floating?

That pull-down would ensure the signal is ground permanently. Not what you want.

James

[jsmcortina]

The hardware manual covers cam inputs. See those sections.

James

[jsdevel]

Thanks James! Also, I realized that I connected the signal wires to analog inputs on my DAQ. Is the output of my CAS digital? (Sorry up front for being a noob)

[jsdevel]

I don't think I had the crank/cam signals attached to my DAQ properly. Also, I was powering my CAS with a PS while the DAQ was powered by my laptop (running off of batter). I believe this is the proper configuration that I should be using.

Screen Shot 2017-03-26 at 1.16.18 AM.png

[jsdevel]

For a noob like myself, I must say that Chapter 4 of this http://www.mccdaq.com/pdfs/DAQ-Signal-Connections.pdf manual is providing some excellent clarification and instruction

Screen Shot 2017-03-26 at 1.20.31 AM.png

[jsmcortina]

To get a signal from the CAS you need a pullup resistor as I said earlier. E.g. 1k 1/4W from signal line to 5V

James

[jsdevel]

I think I get it now. So an open collector switches to ground when on and is otherwise floating. That's why the pull up resistor to 5v is needed to keep the signal either 0v or 5v correct?

[jsdevel]

Success! Thanks for the help guys!

I was able to successfully measure the signal from my CAS and verify that it's working properly. Interestingly enough, I was able to acquire the signal without the pull-up resistors. Another oddity is that using a power drill completely skewed the reading (lots of missing teeth, false fires). I'm thinking the drill was a major source of EMI. Turning the disk by hand with a screwdriver made for a nice clean signal as you can see below.

Previously on my MS install I had been using the 12v source/ground for the CAS; however, powering the CAS with the 5v from the DAQ worked just fine. Would it be preferable to power the CAS from the 5v/ground pair on the megasquirt?

Here is how I had the CAS connected to my DAQ:

cas-daq-connection.jpg

Here's the signal I was able to capture with DAQami (using Channel A0 for Cam and B0 for Crank):

signal.png

[jsdevel]

Attaching my DAQami configuration used for this test.