Rotary Encoder to a Laptop

[djw2k3]

Hi All,

I need to spec some components to price up and achieve the following; Get data from a Rotary encoder to a laptop for data gathering.

This will be a field device (picture someone setting up a stationary wheel that touches an oscillating plate) recording the linear motion via the encoder.

The specifying of the encoder is relatively straight forward; points per rev, IP protection, max RPM etc. The signal out and power supply could be the tricky part for me.

I am rather ignorant of magic boxes that do things for me as a mechanical engineer. So I imagine I will need some kind of converter to take the signal from the encoder and turn it into nice friendly RS232 which my laptops serial port can talk to.

Can anyone help me along the right path or done anything like this before.

Thanks for your time;

Dave

 

[VEBill]

Rotary encoders come in a few different flavours. If you need unidirectional sensing, then you can use the ACP and ARP (ACP=clock pulse and ARP=once-per-revolution reference pulse) interface. If you need two directions, then you'll need something like an I and Q (quadrature) interface. Some encoders provide various outputs covering all the bases.

There's optical encoders and often-less-reliable rotating contact type. I've seen them with as many as 12-bits per revolution (4096 counts).

Some encoders could be interfaced directly into a parallel port making it just a SW project. In the worst case, the OS might decide to wander off and check for Windows updates (or something equally stupid, ie. non-realtime) and thereby miss a few pulses and lose track of where it is. This could be more likely than you'd assume.

I can't help you with the off-the-shelf laptop interface. I'd expect that PCI card interfaces should be available and common (but I haven't checked). USB?

 

[VEBill]

Interesting links:

http://www.gurley.com/MC_Q2.htm#USB_compatible_Virtual_Absolute_Encoder_-_Model_7700

http://www.gurley.com/VH_Key_Features.pdf

There were tons of hits using the obvious search terms on Google: Rotary Encoder Interface USB

 

[nbucska]

as VF wrote, using the parallel port simplifies the hardware to connecting <<8 wires.

Power : from the port. If you need more, use a wall-mount
power supply.

SW: I would boot up and run from DOS,from the floppy
and write the result to a file.


Plesae read FAQ240-1032
My WEB: <

http://geocities.com/nbucska/>