Author Topic: MPU Magnetic Pick Up speed sensor as Plus One MCxxx input  (Read 658 times)

Offline flipper80

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MPU Magnetic Pick Up speed sensor as Plus One MCxxx input
« on: February 18, 2021, 09:45:37 AM »
Hello,
We would like to use MPU sensor (Magnetic 2 wires) similar as Danfoss SB100A as  rpm input with MC controler..
Cannot find how to configure / choose type of input...
Wiring Should we "load" circuit? (saw 1000 Ohms...)
Thanks,
DANIEL

Offline G30RG3

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Re: MPU Magnetic Pick Up speed sensor as Plus One MCxxx input
« Reply #1 on: February 19, 2021, 09:29:14 AM »
No load needed, but I hope your signal will be strong enough because the P/P voltages are very low. (and only sufficient at higher speeds)
You might be better of using a different sensor with a boosted signal or a "hall effect" signal.

Offline flipper80

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Re: MPU Magnetic Pick Up speed sensor as Plus One MCxxx input
« Reply #2 on: February 19, 2021, 01:57:44 PM »
Thanks, but we need to use existing MPU on our machine (BTW very robust and not too much gap dependant...)
What signal strenght is depending on?
In SB100A says 0,4 volt peak to peak "typical"
What type of MCxxx input should be used?
Saying "1000 Ohm load" what does that mean?
Can we adjust MCxxx threshold input?
Regards,
DANIEL.

Offline G30RG3

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Re: MPU Magnetic Pick Up speed sensor as Plus One MCxxx input
« Reply #3 on: February 19, 2021, 02:53:20 PM »
My personal opinion, based on little experience:

0.4V peak to peak with a 1 kOhm load means your peak voltage will be a bit higher with the MC MF input pin
This value is depending on the distance, form and speed of the speedring.

But the minimal threshold to a rising edge is 0.3V in the low voltage range. 
I don't know if all Microcontrollers support Frequency input in Low range
I am sure most controllers don't support frequency reading in high voltage range (experienced this the hard way...)
For a reliable .3 V rising edge detection, you would need about 0.7V-0.8V peak to peak voltage.

Good luck.