Using NPN Encoder Output

A encoder is normally used to provide position information and will normally provide a TTL level train of pulses on two channels. Such information can be used to "count" movements of the driven equipment.

As in 4096 counts on the encoder = 1 revolution of the encoder shaft x the mechanical advantage of the driven system = x number of degrees of rotation on the final driven output shaft.

Are you thinking the voltage level would be proportionate to the rate of change on the encoder? If so, I don't think it will do what you want. An encoder is a binary device, and it output channels are either "on" or "off". The rate of change of one channel relative to the other can indicate direction of rotation as well. Some encoders also have a "home" or "index" output as well.

I'm not sure why you would want this data with a VFD, is it a vector drive? Would not a tach feedback not be closer to what you need?

A little more info would be nice on the application...

hi kamathews, i am thinking you want to keep material at the same speed as the feed or

supply increases or decreases pac

some more info:

The encoder is an incremental encoder delivering a quadrature pulse train into a counter module of the VFD for use as speed feedback.

The variant of the encoder uses a transistor switch to provide voltage levels based on Vcc of 12-24 VDC. Omron (the manufacturer of the encoder) provides 2 variants - a PNP open-collector which pulls the signal high to Vcc or allows it to float to gnd.

Unfortunately a 3rd party supplier obtained the NPN variant that needs to be pulled high to Vcc by the encoder input channel. i.e. the input channel needs to source current. I'm wondering if I install an external resistor to pull-up to Vcc, is it likely to work - If I had the equipment in my shop - I'd just prove it out - unfortunately it's in Far East at the moment (and only partially).

I have also pushed request out to tech support at both Omron (encoder) and Siemens (VFD), but thought I'd pass it by the gang here as well.

Just for some clarity (I hope): The CWZ5B is what should have been ordered, 3rd party supplied CWZ6C, I'm hoping an external resistor will get to a CWZ3E equivalent.

It should work as you expect. Notice the "should". I have also flipped a NPN I/O device in this fashion when needed. Though I must admit it was normally done with a proximity switch feeding a PLC input module.

If I was sending this overseas... I'd get what it was I actually needed and I don't think I would rely on a jury rigged setup. Might be much more trouble then its worth.

That will drive the VFD OK, but the logic sense is reversed. When the encoder goes high, the ouput will go low, so you will be off by 1/2 pulse.

To make an equivilent of the proper unit, you need to also add a PNP transistor to flip the phase back to the correct state.

Yup...

but since the encoder is being used for speed information you really don't care about being 1/2 pulse off.