I was cleaning up my lab at work when I stumbled upon a contraction from a research project that never went anywhere. I got in touch with the researchers and asked them how they wanted me to disposition the equipment. “Don’t need it anymore, just toss the stuff” was the reply.<\/p>\n
So I started to take this thing apart to do just that when I found a black box in the center with a rotating plate and electrical connections. I did a quick Google and found out the box was a motor with optical encoder. The resolution of the encoder is 500,000 counts per revolution! And this was the low resolution model at $5,000. The higher resolution model goes up to 2 million counts per revolution.<\/p>\n
So obviously this did not go into the dumpster. I am now working with it at home to re purpose it for testing I need to do at work. Unfortunately we lost the controls for this rotary stage and the company will not buy them anew. So I am MacGyvering them at home. I can’t drive the motor simply as it requires 300 volts 3 phase power at 3 amps per phase. That is 2,700 watts for a motor the size of a paving brick. But I can use the encoder for feedback and a simple DC gear head motor with a friction drive on the outside rim of the round table. Add an Arduino and like Dave for EEVBLOG says “Bob’s your uncle” (or Robert’s your mother’s brother).<\/p>\n
Tonight I got it powered up, and sure enough the A and B channels are 90 degrees out and it generate very clean TTL signals. I have nothing that can decode the quadrature encoders nor count the pulses, but just from the large number of counts I get when I touch the table, I can believe the 500,000 counts per rotation.<\/p>\n
I have parts on order that should allow me to do the decoding and counting. Then come on Monday so I will have all weekend to drool over the device.<\/p>\n","protected":false},"excerpt":{"rendered":"
I was cleaning up my lab at work when I stumbled upon a contraction from a research project that never went anywhere. I got in touch with the researchers and asked them how they wanted me to disposition the equipment. … Continue reading