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Unread 07-19-2012, 09:37 AM
ryanm222 ryanm222 is offline
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EP4 frequency

Hi,
I am new to this site and new to encoders so bear with me. I am using the EP4-100-079-D-H-T-B single-ended encoder on a 200 RPM motor, and I am not getting the frequencies I expected. I hook one of the output channels to an oscilloscope and get a clear square wave except the frequency is about 1.5 kHz when I am running the motor at about 20 RPM when I excepted the frequency to be about 33 Hz. The encoder is hooked up to a 5V supply as specified. Am I getting the correct output or is something causing the frequency to be high? If that is the excepted frequency for 20 RPM, why is so much more than I excepted? Thank you for any help.

Ryan
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Unread 07-19-2012, 09:51 AM
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Re: EP4 frequency

Quote:
Originally Posted by ryanm222 View Post
Hi,
I am new to this site and new to encoders so bear with me. I am using the EP4-100-079-D-H-T-B single-ended encoder on a 200 RPM motor, and I am not getting the frequencies I expected. I hook one of the output channels to an oscilloscope and get a clear square wave except the frequency is about 1.5 kHz when I am running the motor at about 20 RPM when I excepted the frequency to be about 33 Hz. The encoder is hooked up to a 5V supply as specified. Am I getting the correct output or is something causing the frequency to be high? If that is the excepted frequency for 20 RPM, why is so much more than I excepted? Thank you for any help.

Ryan
Welcome!

Most encoders don't create one pulse per revolution, but rather offer a pulse every portion of a revolution, sometimes 128 or 256. This is referred to as Pulses Per Revolution (PPR). Another unit used is the CPR, or Cycles Per Revolution - almost always four pulses.

That's why you're seeing so many Hz. Just divide it by your encoder's PPR to get the encoder disc's RPS (Revolutions Per Second). You can then obviously multiply it by 60 to get the RPM.

The E4P encoder comes with PPRs between 400 and 1400, and CPRs between 100 and 360. I don't know your particular model's spec.
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Unread 07-19-2012, 09:58 AM
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Re: EP4 frequency

It is 100 CPR (400 PPR) I believe. But if I am only running the motor at about 20 RPM, so the expected frequency should be about 33 Hz for just the one channel I believe.
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Unread 07-19-2012, 09:05 PM
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Re: EP4 frequency

400 Pulses/rev * 200 Rev/minute = 8000 pulses/min, divide by 60 (seconds per minute) and you get 1333 pulses per second (Hz).

Make sense now?
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Unread 07-19-2012, 09:29 PM
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Re: EP4 frequency

Quote:
Originally Posted by DonRotolo View Post
400 Pulses/rev * 200 Rev/minute = 8000 pulses/min, divide by 60 (seconds per minute) and you get 1333 pulses per second (Hz).

Make sense now?
Two problems:

1) he said 20 rpm, not 200

2) he said he put the scope on one channel only. so that would be 200 PPR on one channel, not 400.


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Unread 07-27-2012, 03:38 PM
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Re: EP4 frequency

Quote:
Originally Posted by ryanm222 View Post
on a 200 RPM motor
1. This is what I was reading.
Quote:
Originally Posted by ryanm222 View Post
(400 PPR) I believe.
2. and this is what I was reading.

If those numbers are different, it will be easy to sub in the correct values and see what should happen.
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Unread 07-27-2012, 05:26 PM
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Re: EP4 frequency



The "100" in the part number EP4-100-079-D-H-T-B means 100 cycles per rev. In this context, a "cycle" means:

- a rising edge on Channel A, followed by
- a rising edge on Channel B, followed by
- a falling edge on Channel A, followed by
- a falling edge on Channel B

If only one channel is being displayed on the scope, there will be 100 rising and falling edges per rev, which is 100 cycles per rev.

So the math looks like this:

20 rev/min * (1/60) min/sec * 100 cycles/rev = 33 Hz

... which is what the OP calculated in post #1.


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