Part One of Phase Dock LIVE featuring Walker Archer for a wide-ranging conversation about RC robots, electric wheelchair bases, motor controllers, and “terrorizing children” at Faires and Halloween.
Walker is an systems engineer for the Ford Motor Company. He is an avid software programmer and recent electronics hobbyist. In 2014, he organized the Thunder Ops Makers as an informal “learn by doing” group that has displayed projects for years at Detroit-area Maker Faires.
It has been edited for length, clarity and readability.
We’ve split the transcription into two parts for readability. Occasional time stamps are shown in square brackets [4:52] so you can watch the action and animations as they are described in the video.
Watch the Video
CHRIS: Hi, friends—I’m Chris Lehenbauer, CTO and founder of Phase Dock.
Welcome to the fourth Phase Dock LIVE. We’re excited you are here.
If you are new to Phase Dock, we’re a manufacturing startup here in Raleigh, North Carolina. We focus on single-board computers like Raspberry Pi and microcontrollers like Arduino, BUT…we do more on the mechanical side and not so much the electronics. Because our main product is a prototyping platform, we get introduced to a lot of fascinating projects from some smart, interesting people—our customers. We realized that sharing some of these projects would make a great live stream, and here we are.
So, without further ado I would like to introduce our guest speaker today: Walker Archer. We met Walker in 2019 at the Detroit Maker Faire…held at the Henry Ford Museum in Dearborn Michigan. If you have any interest in automotive and transportation history or technology, the Henry Ford is a “must see” when they open back up again. And the Maker Faire is a great time to be there in the summer.
Walker is an associate architect for the Ford Motor Company. He is an avid Software Programmer and recent electronics hobbyist. In 2014, he organized the Thunder Ops Makers as an informal “learn by doing” group that has displayed projects for years at Detroit-area Maker Faires.
Our other guests are TARA and Lefty… but I’ll let Walker introduce them.
Welcome Walker! How are you today?
WALKER: I’m doing great, thanks! Good to be here!
CHRIS: Tell us a little about yourself, Thunder Ops and how you got into building TARA.
WALKER: I work at Ford Motor Company as you mentioned. I think System Engineer is my official title. It’s a great place to work and do a lot of technology.
Thunder Ops was a group of Makers. Pretty informal. Basically, it started out as a group of friends. We had a few people filter through who weren’t in that core group, but it was mostly just friends who wanted to work on fun things. They weren’t all technical. We had a really good woodworker, a financial analyst. But you know, “making” comes in so many different ways.
TARA and Lefty are fun projects that I did on wheelchair bases. TARA is… Compared to the people you’ve had on this program before, she is very simple. I’d even say she’s one of the dumbest projects that you’ve had on your show. [4:28 TARA enters the frame.]
TARA enters for the first time
I probably should have named her “Dumb-Bot”, she’s that dumb. She hangs out. Her fashion sense is terrible. I don’t know why the black all the time. I don’t know who cuts her hair. It’s ridiculous!
CHRIS: That’s a spectacular introduction.
WALKER: She’s right behind me, isn’t she?
CHRIS: She’s there, so be careful what you say.
We may have made her mad because she’s kind of stomping off.
WALKER: I’ll have to reset her later, I think. I have trouble with the demos.
CHRIS: We’ll talk about the technology for sure, but I’d like to start with how people interact with her. You show her off at the Maker Faire, where there are hundreds of thousands of people. How do people respond to her?
WALKER: It’s shocking how little detail you can put into the actual form of the bot and have people respond to it.
Spiderbot “chasing” a child
The first robot I built was for a friend. We called it “spider-bot.” [5:01] Terrorizing children is just another hobby of mine.
You can see, there’s nothing to it. It’s basically a big remote-controlled car with a Halloween spider stuck on top of it. There’s nothing else to it. But, although it is easy to see that it’s just a piece of plastic, people respond to it in kind of a visceral way.
But even that, you can add personality to it. [5:56]
Child hugging spiderbot
CHRIS: That is the most amazing thing. That little kid hugging the spider. I did not see that coming.
WALKER: Yeah. He hung around for the longest time. He was there probably thirty minutes. Even with all the things you can see at Maker Faire…all the entertaining things…he would keep coming back. He was scared at first. But eventually, he and his father were there and his father coaxed him to hug the spider. Yeah, that was fun.
CHRIS: We also saw TARA in that first video, right? You’ve got routines you do with TARA, don’t you?
WALKER: Yes. She went through three different phases and she’s on her fourth revision now.
In the first revision we tried to do remote controls. [7:11] This was her first version.
She was using WiFi at that point. The astute people out in the audience are probably already smacking their foreheads…as I did later on.
It was really cool. I liked the interface for this. I liked being able to use a tablet. The problem was, when we got her to Maker Faire, people started coming through with their phones, the bandwidth of the radio space was not enough and she became more and more difficult to control.
So, the second year, we abandoned that whole thing.
CHRIS: I do like that interface. It was pretty nice.
WALKER: Yeah, I wish I could go back to it. The beauty of it is that it’s a web page and it’s all being served from the bot itself. A full control surface. It was just a matter of web editing to make whatever features you wanted.
The first case with WiFi
So, this was the first case. [photo 8:44]
It’s a case from Lowe’s actually. I started stuffing it. I had a couple of buck converters and you can see the WiFi fob.
This is what it looked like inside. Not too bad. There’s a BeagleBone Black and an Arduino for some side features.
The buck converters were 9 volt and 5 volt power supplies for some of the peripherals.
Basically, there are two ways to control the wheelchair…well there are probably more than two ways…but one of the ways is to use the existing controller that is part of the chair when you get it. That’s what I did initially.
In phase two, it was hacking that controller. [9:53]
CHRIS: Tell us what we’re looking at here.
Original wheelchair motor controller
WALKER: That’s the wheelchair controller. Wheelchairs have a joystick for driving them around. This is the joystick cracked open and circuit board exposed. There is some charge circuitry on here but mainly controls.
These are soft buttons that you would hit with contacts that would do things like power on, power off, horn, turn the speed up and down. I was using some transistors to flip those.
Then the joystick itself, you can see the back of it here, [photo 10:43] had a nice ribbon cable. So, to hack it, I would just tap into this ribbon cable, and use voltage signals to simulate what the joystick would have done.
Wheelchairs come in a lot of different kinds. This is an old one and the older ones are easier to hack the controllers. The new ones use CAN bus, or a variant of CAN bus. The SharQ controllers for instance use a CAN bus that has special timing on it so they make it a little more difficult to do anything robotic with it.
You can see this cable here, a secondary cable that would be just running down to the case.
CHRIS: Is that a proprietary CAN bus documented enough that you can hack it?
WALKER: Not really. This equipment is medical equipment, so they are not real forthcoming with information that they consider proprietary, that a competitor could use.
CHRIS: The reason I asked that is because the wheelchair is such a beautiful Maker platform. You’re saying it can carry 350 pounds for ten miles or something, right?
WALKER: Yes. Some of the best wheelchairs can go ten miles on a charge. They are built to carry people who are sometimes quite large so 350 pounds is a pretty common weight limit. I actually tested the wheelchair on the shark by driving myself around our neighborhood…to my wife’s chagrin. I’d go at night, when it’s dark, so I could sneak around the neighborhood. It went six miles on a charge.
CHRIS: [13:04] My take-away from that was, if you can find and hack a wheelchair base I can see all kinds of possible applications for that.
WALKER: The advantage to hacking the existing controller is that it has a lot of safety features built in. It limits the amount of voltage you’re going to get through the wheels. That’s a plus and a minus. There are usually wheel brakes so they lock automatically when you remove the power. That’s so if someone is going up a long hill and the battery gives out, they will stop and not roll all the way back down.
CHRIS: If you keep the controller intact, you keep all those features and you can get at them?
WALKER: Yes. And that was my thought, starting out. It was safer. This is a hacker project. This is true “make” going in and trying to reuse things and learn the electronics that have already been built.
In the last revision, I have gotten rid of that. And the reason was, the signal from the radio controller (RC) had to go into a receiver and into the computer where the PWM signal from the receiver had to be interpreted. There were a few steps it had to go through, so there was always a bit of a lag in the control process.
CHRIS: Do you have a picture of how that evolved?
WALKER: Yes. [14:54 video of TARA surrounded by children] This was TARA at the Shell EcoMarathon at Detroit Mobile Hall, I don’t remember the year, but it’s an amazing event.
CHRIS: She’s drawing quite the crowd.
WALKER: Yes, she draws a big crowd. She had a voice at that point, but it wasn’t very good. The speakers were undersized. We didn’t have a big enough amp for it, so everybody had to crowd in to hear what she was saying.
CHRIS: Look at the faces on the people, particularly the kids. Everybody is smiling.
TARA and her fans
WALKER: Yup. Here’s another photo at the same event. [15:39]
You can kind of see how the controller is on the back.
Typically, when I take these robots out my goal is to have three at any event. Then, I’ll recruit drivers to take them around to different spots at the event. So, we’re running in different places.
[16:15] This is one of the drivers. He happens to be an electrical engineer at Ford as well. That was the “paddock” which is where they’ve got all the EcoMarathon vehicles.
WALKER: [16:37] This was her control box. [Shows two photos.] I don’t have a wide shot of this. But you can kind of see how, as things change, you change your idea about using WiFi. The whole project evolves over time, it just gets more and more crowded. That is what is happening here. I don’t even know what these two wires do anymore. They were for something I was working on.
Eventually I decided it was not a good idea to do WiFi. And I added better sound and an amplifier. Again it’s a fairly simple project, but we ended up with this. Let me share another camera. [17:32]
This is what happens when you run a project for too long.
CHRIS: That’s a fair amount of spaghetti, I’ll give it that.
WALKER: I had a clear plastic cover on this so that people could see inside. I’d often get people who wanted to see the electronics. I’d bring them over and show them this. Their faces would go blank and I would not get any more questions.
It was obvious that I had to do something with this.
When you came up at Maker Faire Detroit and showed me your product [the WorkBench 1107W inside a NEMA box], that was it.
CHRIS: I remember that moment. It’s still gratifying. That’s why we started the company…to solve problems. When it actually happens, it’s a good day.
WALKER: I’ll bring TARA over. I’m going to park her under the down camera.
That’s what it looks like now. [18:54]
TARA’s current controller
This wire runs power to TARA, but my goal is to get all of these cables managed a little bit better.
We’ve completely gotten rid of the original wheelchair controller now.
[19:20] This is a Basicmicro 2X15A [2 channel, 15 amp] motor controller. The RC goes direct to that. As you can tell by her movements today, the control is so much more responsive. A lot safer, I think, than having the lag times. Especially where she is around people all the time. You really need to have a good control over the motion of the robot.
This is a BeagleBone Green [19:54] One of the really nice things about the BeagleBone is that it is truly open source. You can download the Gerbers. You can send them to somebody to print. Populate it yourself or have them populate it.
Companies can download those Gerbers if they have something that they want to integrate. They can change the design. BeagleBone Green is produced by Seeed Studio. That’s a perfect example of that open consideration.
CHRIS: They do a good job. One of our collaborators has had some PCBs done by those folks and they do a really nice job.
I’ve known about BeagleBone for a while. We have one here, but I’ve honestly never used it because I do almost everything I do on Arduino.
But you explained to me that the BeagleBone is essentially a cross between an Arduino and a Raspberry Pi because it’s got both a general-purpose computer and microcontrollers.
WALKER: I want to say, I like the Raspberry Pi, too. I like having options and different tools. In my toolset, I have more than one screwdriver. They are good for different things.
I really like the BeagleBone for this project because this project takes a lot of vibration as it is rolling around. And this thing runs super cool. It just fits here.
But you are right. It has a main processor, which drives the Linux side of it. It also comes with two microcontrollers, called PRUs. Programmable Realtime Units.
They are sort of like an Arduino, but not as easy to program as an Arduino. There is definitely a learning curve to programming them. They are deterministic, so you can put things on them that require real-time processing. They are mostly to do things like program peripherals—driving serial ports or whatever. In this case, I’m going to use it to read the PWM from the remote-control unit. They are perfect for that.
END PART ONE: Read Part Two