WonderCon was last weekend, and it was my first real test of Artoo since the rebuild. I’d mentioned that both Gerard and I had problems with our batteries. We’d figured it much be the carpet, but I hadn’t had the problem at Celebration 4 - and in the back of my mine I had a niggling theory what was causing it.

For Celebration 4 I’d used 3 7Ah 12V batteries, two dedicated to powering the NPC-2212 drive motors, and one for the body electronics like the sound system, dome drive and speed controllers. But during the rebuild before WonderCon I’d decided to consolidate all 3 batteries into one block to make charging easier. I’d had issues with power before, but thought the problem was resolved and I could consolidate my battery sub-system. Runtime at WonderCon was approx. 60 minutes vs 180+ minutes at C4 - which is a huge difference.

Unfortunately, while I was redesigning my electronics and adding the charging system, I’d forgotten that the RoboteQ speed controller really likes a solid 12V supply, so last weekend as my batteries ran down and when the NPC motors first start-up they were eventually pulling the supply well below the minimum 10.5V required by the controller. It’s “intelligent” and shuts down if it thinks it doesn’t have enough power to control the MOSFET drivers. It’s only for an instant, and starts back up almost immediately as power is cut to the motors - which resulted in the very slow and slightly jerky movement.

So today to prove my theory, I reinstalled the the “dead” batteries from last week without recharging them, and added a separate 12V battery to the Power Control lines on the RoboteQ - Bingo! Worked first time. The issue was totally gone.

I’m kinda embarrassed that I went through this, because I should have remember that there’s a know “design feature” with low batteries and high current draw on this type of speed controller.

I’m now confident that I can pretty much run Artoo for multiple hours on a single charge - but I will have to reconfigure my electronics system again - making it harder to charge batteries in place.

Related Posts:

• WonderCon 2008 Show Report
• Updated Charging System Circuit
• RoboteQ 3500 code 8 fixed
• Artoo’s First Steps

Not a whole lot going on. I did find a very cool surplus electronics store this week in Santa Clara called HSC. They carry a LOT of stuff at a fraction of the cost and the place is full of things that can be used on R2. I was hoping to find a slip ring to experiment with but I was out of luck. I did pick up a few bits though, including some red rectangular LEDs for the front slot on the periscope.

I did a quick test fitting on my aluminum periscope housing and they fit perfectly.

There’s very little published reference material for the periscope, but I have it on good authority that the front red light was made up of 6 of these LEDs.

I also worked a bit on my RoboteQ speed controller, adding a RS232 connection to the provided PWM cable to allow me to monitor things live from a tethered laptop. Basically I ran two wires (RxD/GND) from the 25-pin plug they provide to a 9-pin RS232 plug/housing.

The plug you see on the right may look like an RS232 connector, but it’s really used to connect just two PWM wires from the Vex receiver into the RoboteQ. It comes as standard with the controller, and they also provide a seperate RS232 cable to connect your computer. I really don’t understand why they don’t just provide one combine cable. Confused? Please see the RoboteQ manuals

Once the controller is connect to my computer I can use they’re monitoring software called roborun. It polls the speed controller and graphs live data like battery voltage, controller temperature, current being used, PWM data etc. It also allows me to exercise the motors without using my RC transmitter.

I’m back from C4 and R2 performed really well.

I was able to finish the basic structure, the dome, the electronics and he was fully RC’d and running around most all of the days at the con. As you can see I also fixed the dome and got most of the blue painting done. Battery life was excellent and the Roboteq AX3500 speed controller / NPC-2212 combo worked out great. I was in both races and the little guy far exceeded my expectations of what I thought I’d be able to do at C4.

This is me driving back to the hotel on the last evening ready for transport back to the Bay Area - Yes I drove him home 1/2 mile to the hotel without incident.

I still need to sort through my photos and upload them and post a full write-up, but wanted to post something other than having my dented dome as the top post in the blog

I also intend on going back and catch up with blog posts on all the building I did before I left.

Drive system jerkiness is all fixed. The problem was the AX3500 and not a Vex compatibility issue. The board had a dry joint on the main power control tab which was causing a short. The speed controller thought the battery was low which cause the fail safes to kick in and turn everything off to avoid damaging the Mosfetts.

I’d gone back and forth on the phone with RoboteQ for a few days, and finally they just overnighted me a new board which fixed the problem instantly. While I was removing the cables to send the old board back the tab connector popped off the board totally.

In the process of troubleshooting the problem, they also convinced me to reconfigure my batteries to have a dedicated 12V supply to the board rather than using a single shared 12V supply for everything. They explained that the symptoms I was seeing were very similar to a low battery problem due to the motors drawing too much current.

I’m probably going to keep the batteries separate for now, but will have to rethink the wiring and my fuse block as I was hoping to just get away with one battery feed which also made charging easier.

The real worrisome thing is he’s way too fast and really dangerous. He can zip around at lightning speeds and can plow through most obstacles because of his weight. I may need to have a fast/slow switch.

He’s also shacking himself to pieces and has already dropped several screws.

I received my center foot on Friday and it was the last structural part that I needed to get R2 on all 3 feet. So, my goal for Saturday was to get him running around under his own steam by the end of the day. I still needed to wire in the RoboteQ AX3500 speed controller which controls the drive system.

I added a power strip to the inside of the back mounting plate to connect all the grounds to and set about wiring things up.

I then did some basic tests of the 3500 and noticed something strange. The motor would run for a second then stop for a split second then start again, like it had a slight tremor. Message code on the 3500 status panel flickered from motor direction information to an ‘8′ - which means under or over voltage. I suspect it’s a low battery. I hope it’s not a Vex/RoboteQ incompatibility problem. I suspect I may need to add a second battery dedicated to just controlling the 3500.

I then worked on trying to get the center foot assembled and attached to the frame. But there was a problem, I was missing the pack of hardware. A quick trip to Ace fixed it, but I couldn’t get the exact parts and had to improvise on the standoffs.

Like the outer legs and feet the new foot was a snug and it took some cajoling to get the pivot point to fit.

Now that the center foot/leg was attached I was excited to think I was close to getting him mobile.

However I really shouldn’t have rushed as much as I did. What followed was a bunch of silly mistakes which cost me a lot of time. Luckily no harm was done and I learned a lot in the process.

Even in my haste to get the legs on and the motors hooked up, I’d remembered that I needed to lock the legs somehow. I’m not going to be using the satellite motors to do 2-3-2 at this points, and one of they’re jobs in the design was to lock/hold the legs in place. So I knew I needed to figure something out, but I thought it wouldn’t hurt to skip this step just for now. Boy was I wrong!

At the same time I also had the drive wheels in the back of the feet, and they weren’t always touching the floor. I’d also forgotten to reverse the drive wires on one motor.

As you can imagine his first steps were not pretty to say the least and he jerked around because of the RoboteQ battery problem, and his legs went in opposite directions. It was a total shambles. Luckily I didn’t have the camera handy for a photo.

I also needed to tension the drive belts more which meant that I had to partially disassemble the feet again. I’m beginning to realize it’s a major pain to unscrew so many bits just to fix one thing.

After stripping him back down and fixing the problems and locking his legs back in 3 legged mode I gave him another spin and here he is. He’s super fast, but I really do need to figure out the battery/undervoltage problem that makes him stop/start/jerk.

Once I get the RoboteQ speed controller working correctly this thing is going to scream.

Another big step forward tonight and I’m not really sure where to start or if I can remember everything I did.

Maybe it’s easier to say where I’m at - I now have a lot of the electronics installed in the body, from fuse block and power distribution to the speed controllers and sound system. I can now control the dome and periscope from my Vex transmitter and trigger sounds with my RF remote.

There was a lot of stripping of wires, routing them, testing, and moving stuff around to make it all fit on the back panels. I also installed a second Vex in the dome to control the periscope, and eventually it’ll control some servos on the pie-panels.

From the photo it really doesn’t look like a lot but there’s a lot packed in there

I’m now realizing that it may not be a good idea to run R2 around naked / skin-less at C4. I could easily see someone pulling on the wires and frying something.

Here’s a quick demo video as well.

You’ll notice in the video that the periscope doesn’t run up and down smoothly and it chatters. Some of it is due to the speed the motors run at which I can limit in the Vex, but there’s also a lot of play in the lift mech screw system itself which I need to fix somehow.

I still need to wire in the RoboteQ speed controller which will drive the feet, but you can see it at the bottom of the frame.

One problem I noticed again is that the Vex in the dome has problems receiving a signal. This maybe a big show stopper unless I can route the antenna somewhere else.

The 12 channel RF Remote also has a “problem”. The new models have a little speaker/siren on them which makes this awful bleep every time you press a button on the remote - I’m sure for most applications this is fine, but for R2 it’s got to go. You’d think it could be disabled easily, but I can’t find anything. I’m going to have to fix it before it drives me nuts.

A couple of people have written and asked how I configured the SyRen10 Speed Controller and how I connected it to Vex Micro controller, so I thought it best to document it here for future reference.

Setup and wiring was very easy, and I simply went through the online SyRen setup wizard and picked logical answers.

As you can see all but dip switch one are set to ON.

And here’s how the controller is connected to the Vex

There’s only 4 other wires needed, 2 to the battery (V+/-) and 2 to the motor (M+/M-)

Big milestone for me tonight. I finally got around to wiring up my dome periscope lift mech to a speed controller and my VexLabs RC setup.

This is my first time wiring up anything like this, so I was a bit apprehensive. The good news is I didn’t pop anything and it worked first time.

I was really surprised on how fast the little motor spun the mech up and down. So fast that the threaded rod squeals a bit. I may have to program in limits on the controller to cap the max speed.

Here’s a quick photo of the test setup and a video

For the test I used a SyRen10 Speed Controller.