Torque Coupling Update

smackaay — Mon, 24 Nov 2008 18:57:41 +0000

This update is a little bigger than usual since I want keep the images and text as a sort of record of what I did for future reference. For the viscometer project, I’ve discovered that the motor is far too unreliable to produce reliable results despite algorithmic compensation. So now I’ve been charged with the task of creating a torque coupling that fits on to the rotating shaft. Now, there is no problem building the torque sensor, however, what is a problem is making it small and making it send the signal back to the device.
Also, instead of using an Analog Devices AD7705B 16 bit serial out ADC. Frankly, I’ve never used one but the greater resolution should enable more useful measurements.
Anyways, here’s a picture of the torque coupling before I ravaged it with hot glue.

Torque Coupling

It’s pretty fucking ugly but it’ll work for the time being. I did have the ribs that sit under the sensors quite a bit thicker, but there wasn’t enough strain to be useful for measurement, I had to hacksaw the chunks underneath right off.Unfortunately, I believe the polyurethane glue I used has caused strain on the sensor as it cured, I don’t know of it will go any further.

So, I’ve started on the circuit as of yesterday. I have it set up to take the PICKIT2 interface so that I can hot-program it and I setup the serial out board so that I can output debug data. This works thus far. Soon, I’ll be setting up the ADC and attempting to interface with it.

Starting on the ADC circuit

Here is an image dealing with the read/write cycle on the AD7705, also to note is that the AD7705 is MSB first.

The timing for read/write on the AD7705

Here’s the site they came from http://www.protongeeks.com/index.php?option=com_content&task=view&id=63&Itemid=27

Anyways, I’m glad to have my equipment back and ready for whatever crap I decide to build. Here’s a picture for posterity:

My bench as of Nov, 2008

Anyways, I’ll attempt to update this as much as possible, for whoever is interested (or not).

Steve's Junk » ad7705

Torque Coupling Update