Building an Inverted Pendulum System The Ups and Downs of Defying Gravity…

A friend with the proper equipment drilled all the holes in the aluminum bar and attached it to the rack gear.  Now I just need to pick it up.

Won the bid on the new encoder on ebay.  It was a bargain at $18 including shipping.  At this point, I am going to quit trying to get the broken encoder working.  It is still a possibility but not really worth pursuing unless I need a replacement encoder.

The LEDs came in today.  I soldered a resistor onto the positive lead of each LED so they would work properly with a 5 V power supply.  I connected each LED and tried waving it in front of the encoder sensor.  All of the LEDs managed to make the digital signal flicker, so it looks promising.  The problem is that none of them was consistent.  I couldn’t get a good steady signal on both A and B channels at the same time.  I suspect if I drilled a hole in the side of the encoder where the old LED is, I could put a new LED in the same spot and it might work.  The light would have space to spread out and go through the lens and be focused on the sensor.  Drilling through the side of the encoder would be a little risky, though.  I am leaning towards just getting a new encoder if I can get one at a reasonable price.  Most of the ones on ebay are priced higher than I am willing to pay.

Sigh.  Just found out that the sbRIO board from NI is not working and needs to be repaired.  That means it will be a while before I can start controlling the system.

Realized that the original bad encoder (#1) probably has a working LED, while the encoder I broke (#2) has everything but a working LED.  Thought maybe I could move all the working components from #2 to the case of #1.  Started by removing the retaining ring on #1, then pounding the shaft out of the bearings.  Managed to remove the shaft, then the two ball bearings supporting the shaft.  At this point, realized there was no way we could get the shaft with the glass encoder disk out of #2 and into #1 without destroying the glass, which is very thin.

Ordered several different infrared LEDs from Digikey for about $5.  Hoping one of them will work with the broken encoder.  Not sure if the light needs to go through the lens or if the LED can be close to the sensor.  This is a last ditch effort, but I really can’t lose for just $5.

Placed a bid on ebay for a DRC encoder that looks like it will replace the broken encoder.  Same size shaft and has the differential signals I need.

Encoders not quite as bad as I originally thought.  I decided if I could remove the circuit board, I could fix the solder beads on the back of the board and reassemble everything safely.  Started by scraping off all the glue around the edge of the circuit boards.  After a little trial and error with the original non-functioning encoder (and shattering the glass disk on it), I figured out how to pop out the circuit board.  Cleaned up the solder on the back of the boards and reassembled everything.  One encoder works fine now – it has good signals and turns smoothly.  The other encoder still doesn’t work.  It turns out that when I popped out the circuit board, I accidentally yanked one of the wires off the LED which is at the bottom of a deep, dark hole with a lens above it.  No way to possibly reattach that wire.  At least now I only need to buy one replacement encoder.

Today was a bad day.  I decided to replace the cables on the encoders today.  Heated up the soldering iron and got to work.  Removed all the wires from the first encoder, then attached the new wires.  After reassembling everything, I noticed it was very difficult to turn the encoder during about half of each revolution.  Since it was the one I tested with the motor, I thought maybe I had bent the shaft due to a misalignment of the gears or something.  Resigned myself to the possibility of needing to purchase a replacement encoder.  Started on the second encoder a little later in the day.  Removed all the old wires, then noticed it was difficult to turn the shaft on this encoder also.  What I hadn’t realized on the first one was that the glass disk for encoder is directly underneath the circuit board.  When the solder was heated up and melted, it formed a large bead on the back of the circuit board which is now rubbing against the encoder disk.  Both encoders are ruined unless I can find a way to fix them.