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Merkle-Korff motor and tachometer

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andrey8

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Hello. I just purchased a Merkle-Korff DC motor(EY series) from a surplus store. It looks like it has a tachometer or encoder attached to it.
Here is a picture and some specs:
http://65.61.11.207/productpages/eyqm63264.htm

I found the specs for the motor on the Merkle-Korff website
http://www.merkle-korff.com/modeymatrix.htm , but couldn't find the specs for the tachometer. Has anyone used this type of a motor before? Can anyone suggest a spec sheet for the tachometer? Thanks.
 

ChrisP

Member
Specs are on the manufacturer's optional accessories page, available from the page you linked:

TACHOMETERS AND ENCODERS
Magnetic Tachometers • 16 pole AC tachometers (8 cycles/revolution) are available with motor models EYQM and CYMM • Tach voltage: EYQM 1.8 vrms per 1000 rpm typical • Tach voltage: CYMM 3.3 vrms per 1000 rpm typical • Addition of the tachometer will add approximately .50" (12.7 mm) to motor length on Model CYMM and up to .30" (7.6 mm) on Model EYQM
 

andrey8

New Member
Merkle-Korff Tach

Thanks for the reply. I saw those specs too, but that is not enough information. If you look at the picture, the motor has 4 leads. Two of the leads are red and black(I am assuming that these are the power and ground connections) and two of the leads are green and yellow. I need to know which of these leads is for the signal generated by the tach? Are both of them signal leads? Are the power and ground leads common to both the motor and the tach? Also I need to know what kind of a pulse is generated by the tach, a sine wave, a square wave? Is the signal conditioned with an internal Schmitt trigger?
 

andrey8

New Member
Here is a reply that I received from a Merkle-Korff rep regarding this, if anyone is interested:
"The black and red leadwires are for the motor and the green and yellow leadwires are for the tachometer. The green and yellow leadwires are the signal wires. The tach output is 5.5VAC min at 3,000 rpm."
 

ChrisP

Member
Re: Merkle-Korff Tach

andrey8 said:
Thanks for the reply. I saw those specs too, but that is not enough information. If you look at the picture, the motor has 4 leads. Two of the leads are red and black(I am assuming that these are the power and ground connections) and two of the leads are green and yellow. I need to know which of these leads is for the signal generated by the tach? Are both of them signal leads? Are the power and ground leads common to both the motor and the tach? Also I need to know what kind of a pulse is generated by the tach, a sine wave, a square wave? Is the signal conditioned with an internal Schmitt trigger?
The tach output is stated as being an AC signal -- without any other specificationas to waveform, it's a safe bet that it is a sine wave (or nearly so) output. As to lead assignments, the red is going to be +DC, the black is going to be -DC, and the yellow and green will both be used for tach signal. As an AC signal, it is non-polarized. Two leads are used as it is not using a common return (ground) lead.
 

andrey8

New Member
Ok, I checked it with a scope. The tach outputs a saw-tooth wave. Now the question is how do I interpret that with my microcontroller? Should I go through the A-to-D converter? I am using an HC12 board, the DP256 version.
 
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