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split13
08-18-2008, 08:37 PM
Hi, I'm looking for a way to read 5 quadrature encoder. I saw the phidget single encoder reader but I'm sure there is another way then use 5 usb slot. I also found us.digital 4 encoder reader but it's expensive. Is someone having another solution ?

ScuD
08-19-2008, 12:20 PM
A microcontroller perhaps ? You'd probably want one with multiple hardware counters with external input, since you don't want them to interfere with one another.

Another solution is to sacrifice accuracy for ease of use and speed, by reading one encoder after the other, but that would mean you'll drop 4 measurements in every 5 you'd read.

Hephaistos
08-19-2008, 12:51 PM
Hi, I'm looking for a way to read 5 quadrature encoder. I saw the phidget single encoder reader but I'm sure there is another way then use 5 usb slot. I also found us.digital 4 encoder reader but it's expensive. Is someone having another solution ?

I don't know of any inexpensive "drop-in" devices that allow you to easily read multiple encoders through one USB port (other than a USB hub : ) ... of course that doesn't mean they don't exist.

As far as what I could recommend, if you're handy with embedded devices, you could program a microcontroller to handle this and then write the code to interface the microcontroller to the PC. Of course this is a lot of work in and of itself to solve this one problem.

Alternatively, you could look at using U.S. Digital's absolute encoders (the MAE3 (http://www.usdigital.com/products/encoders/absolute/rotary/kit/mae3/)'s). They come in an analog version that you could plug directly into a Phidget 8/8/8. The only down-side to this approach is that it won't work well for fast-moving applications (because the Phidget isn't fast enough). But they work very well if you're connecting them to the end of the drive train (already geared down). I use them to provide feedback for large motors in a servo-operation, so my speed is low. The absolute encoding is also a huge benefit over an encoder's relative positioning. Whether this is an advantage in your application I cannot say.

Adrenalynn
08-19-2008, 02:09 PM
You can also get away from the Phidgets and move to a faster microcontroller. ;)

Hephaistos
08-19-2008, 03:03 PM
You can also get away from the Phidgets and move to a faster microcontroller. ;)

I know, I know...but it's hard to beat a little device that you can just plug into a USB port and start banging out C# code against. But really, the main problem I had was not the speed but was more that the place I had to connect it (to the back end of the motor spindle) made it spin more than 360 degrees. So at that point I lost my abosulte positionining. I ended up replacing it with one of those nifty rotary softpots (which I noticed Trossen recently started to carry, which is Awesome!).