I stripped my first set of gears in a motor this weekend. I was goofing around on the driveway showing Artoo to some neighbors across the street when suddenly the dome stopped working. I heard this really bad crunching noise then a very quiet motor spinning.

I quickly pulled him into the workshop and the dome off to see what was up.

A couple of months ago I had lined the inside track of my dome bearing with some batting tape to help the dome wheel grip. It had been slipping and the resulting noise was very annoying. The tape seemed to be the perfect solution …… until the gearbox failed.

I think what had happened was I’d left R2 sitting in the van all day and when I finally unloaded him the glue on the tape had heated up and when I started to spin the dome it balled up – jamming the wheel and breaking the gearbox.

Gerard had a similar failure trying to fix the squeaky slipping wheel. He’d over tightened the tension spring which stopped the dome the moment the motor stopped – but again this put extra pressure on the gears in the Pittman motor causing them to fail.

So for now I’m back to having a squeaky dome.

The last couple of weeks I’ve been busy getting Artoo back together for a couple of important events. I’ve totally overhauled the electrical system (again) and I’m hoping this will be it for a while.

At the hospital visit on Saturday I ran Artoo for about 4-5 hours on the new system and the 18Ah batteries without any sign of slow down, and I continued to run him again the next day for few more hours on the same charge. I must admit that I didn’t do lots of long sprints, but I’m confident that my earlier battery problems are fixed.

With that said, here’s a summary of the electrical work and the new electrical system design.

The following schematic outlines the 3 main areas of my setup. The red area is the front charging port, flashing LEDs and the battery select/on/off switch. Yellow is the wiring harness/relays that does all the magic of switch batteries between charing mode or running the droid, and finally the blue on the right is the rear electrical panel containing the speed controllers, fuse block, battery monitor, and power distribution board. It also contains an additional relay/power jack to run the drive from 120VAC/12VDC adapter.

There’s also a PDF version that maybe easier for printing.

Here’s a photo of the battery select relay/wiring harness (yellow section of the schematic). It uses 3 automotive relays to do the battery switching for charging and to turn Artoo on and off.

I attached the wiring harness to the battery holder using a small bracket

And here’s the new batteries in place

This is the front charing port (red section on the schematic) you’ve probably seen before. The attaced board to the right is the PICAXE controller that flashes the lights when the front door opens, and the smaller board to the left just contains a 7805 5VDC regular to power the PICAXE. The wiring harness above connects to to the charging socket.

In addition to adding the extra relays to switch two sets of batteries, I replaced the large MAXI fuse block/voltage display with a much smaller ATO fuse block and a separate LED voltage meter display.

I mounted the voltage meter on the rear electrical panel, and instead of using one for each of the batteries I decided to use just one with a switch to flip between batteries. The board requires a separate 5VDC supply to operate and I got this from the power distribution board.

Here’s the new rear panel. Going clockwise, top left is the battery monitor, then the Vex Micro-controller and receiver, below that is the power distribution board, and below that the fuse block, to the left the RoboteQ AX3500 speed controller for the drive motors, and above that the Syren10 speed controller which turn the dome.

I also worked on getting the slip ring soldered up and installed.

And I made up little boards for it to plug into. 12VDC power is connected to the blue terminal block, and the control/servo cables on the 3 pin connectors.

There a very similar board in the dome, but with an additional 5VDC input from a 7805 regulator IC to power the servos.

Here’s a couple of new shots of me and Artoo

Artoo, myself and members of the Rebel Legion’s Endor Base visited Lucile Packard Children’s Hospital yesterday.

It was a great day and Artoo was a big hit with the children and adults alike. This is definitely something I want to do again.

Unfortunately we don’t have many photos as camera weren’t allowed around the children for privacy, but we did take this quick shot at the end of the afternoon.

Just a short video testing out the newly mounted slip ring. No power is being routed yet, but I wanted to see how it worked in place and if there was any pulling on the cable.

I really am building honest and Artoo is back on the workbench.

I’ve revised my battery charging system and in the process of making a new harness for the larger batteries. I’m also reworking my fuse system, so basically everything had to come out. This may look like a mess, but I know where everything goes back honest!

The new battery harness is designed it in such a way that I can mix my old 7ah batteries  and the newer 18ah. I added a little arm that folds out and holds the smaller battery when needed.

Here it is with mixed 18ah and 7ah batteries in place

Arm out of the way and two 18ah batteries this time

Tonite I’m hoping to finish up the re-wiring.

I cut the hole for the slip ring tonight.

Started off by marking the center lines and then using a hole cutter to score the 7/8″ outline where the slip ring body would sit.

I then marked off and drilled holes where the slot would go for the cable plug to pass through

I used a Dremel and a hand saw to join the holes up

You can still just see the outline of the circle I’d marked

I then took a file and made the small circle notches either side of the slot to accommodate the slip ring

Testing that ring slip ring fit and that the plug will pass through

Top view of the slip ring secured in place

Now to solder up the connectors

I started work on my test slip ring tonight and hope to get it installed in the next few days and report back on a new group order.

The sample slip ring has eighteen 2A circuits and I plan on grouping together 6 or 8 for the +/- 12VDC uplink to the dome, leaving ten circuits for PWM/servo signals. To save on circuits I’m not planning on routing the +/- 5VDC from each of the PWM pairs through the slip ring. As a result each RC channel will require just one wire allocated on the slip ring. I’ll just tap of the 12VDC in the dome and re-create a separate 5VDC supply for the servos.

Out of the box the slip ring wires are loose and really needed protecting.

I bought some braided expandable nylon wire wrap from a local surplus electronics store for less than a dollar.

I wrapped the ends in electrical tape to hold things in place.

Now that I have the wire wrap in place I can start soldering the wires to the connectors.

Here’s an overview video on how I plan to implement the wiring