The Mobile Desk Chair Project

Parallax has recognized this project! The page is on their site, here: Mobile Desk Chair.

Back from school for the winter, and some new developments are underway.

I suspect that some drastic changes are going to have to be made to the 'black box' now. I just got two Motor Mind B motor controllers from DigiKey, and these are going to greatly simplify the entire relay/hack speed controller/second relay hookup that I've been fooling around with. I'll upload a picture of these soon.

My only concern is that the speed controllers are only rated at 4 amps of continuous current. I'm not sure how much the wheelchair motors pull, but I'm pretty sure it's hefty. The controllers might be underpowered. I figure at worst, however, I'll just have some underpowered motors. The gearboxes use worm gears, anyways, which I believe reduces the torque strain on the motors and might help alleviate their amp load.

So these next two weeks or so I'm going to be reworking the entire schematic and and black box assembly, which is going to require some more trips to RadioShack and some time on the bench.

I finished hooking everything up this morning. I think I've finalized the code for the BS2sx (I'll be posting that soon). All the connections were made, and I was ready to go.

I took my batteries that I had been charging overnight, plugged everything in, and... nothing happened. It turns out that the charger actually didn't charge the batteries for some reason or another. I'll have to check into that.

So aside from a cranky battery charger, I'm ready to get this chair motile. I hope that the pictures of the black box that the BS2sx is in have helped a bit.

The other side of the box, showing the power switch and the DC power jack that powers the glove.

A side view of the box showing the DC converter on the left, and the two relays on the right.

This is the black box that houses the BS2sx, the two speed controllers, the relays, and the DC converter and power switch.

Just a small update: I've finally finished the connections on the box. Everything is set to go; I just need to charge the battery and hope that nothing blows up. Pictures are coming.

Good news and developments:

I was busy this morning putting on some connectors and soldering some wires as I get closer to having this chair move. I finally got the battery connector onto the black box with the BS2sx. I hooked up the battery, turned on the stamp, and hoped for the best...

Which is what happened, sort of. I hooked up a voltmeter to see what was going on, and it turns out that all of my connections are working the way they are supposed to. What went wrong was that the battery was dead and wasn't putting out enough juice to even make a motor do one revolution. So the relays didn't toggle, because there wasn't enough power to switch them. But voltage was flowing, and so after I charge the battery it will work.

Right now I need to make an order from Digikey to get some more terminal plugs so that I can hook up the other motor. Right now I only have one motor connected to the box.

I know that all of this is horribly confusing without some pictures to help clear things up, so I will be posting a lot of pictures very soon.

Ok. It's been a little while since the last update. Here's what's new:

First off, the chair is still not running yet. Yes, I have been working on it. But it goes slowly. And there's a lot of stuff that I didn't think about before. I think I have one of the motors completely hooked up. I still need to do the other. And I know that there is a resistor that goes somewhere in the circuit, but I have to figure out where and put it in.

On a more positive note, this project recently got supported by Parallax. The project now has its own page under the Customer Applications section, at this page that explains the project. It also has a link to this page. As a bonus, I got $150 worth of free hardware. I used it on a CMUCam and a floating point coprocesser (that allows really high-level math operations).

So now I have a CMUCam, and a cool Noritake VFD display - similar to a graphic lcd display. So now I basically have everything I need to make the helmet for the chair, and to hook it up. All that's left now is to actually do it.

However, I'm going to be heading off to school for the year, and I can't bring the chair. I will be bringing the CMUCam and maybe the display, though, so I may still be able to do some work on this project while I'm there.

Ok, so the last post was a little ambitious. Maybe too ambitious.

But I've been thinking about the next step, because it's getting close. Right now, all that stands between me and a mobile chair is connecting the motors to the relays. Everything else is ready to go. Well, debug might take a little while - I still don't know exactly how this chair is going to react to the movement of the glove - but it's all manageable.

So I still like this idea of using the CMUCam to give the chair the ability to see what the driver sees. I think I'm going to scrap the idea of having a viewfinder for the driver. I've tried looking around, and that venue looks a lot harder than I first thought. So, to continue this idea of having a helmet (like a motorcycle helmet) for the driver, here's what I think:

• Have the CMUCam mounted somewhere on the helmet on some servos or something so it can move independently of the helmet if it needs to.


• Get another Stamp module from Parallax to read the camera and to interpret it. I'm thinking a BS2p or something else really good and fast.


• Now here's where the user will get to see some information from the camera: I want to have an LCD module or something (a black and white one - not video or full color) mounted inside the helmet or right on the visor so that it becomes a heads-up display. This will have information like the center of the object that the camera is tracking in relation to what the driver sees, the color of what it's tracking, and any other information I can get. In addition, I might have other LCD modules to display other info, like motor speeds, glove tilt, ambient temperature - anything else that's cool. I'm currently looking at displays from Noritake.


• In addition to all of the visual stuff, I'm thinking about incorporating an audio element as well. There are speech recognition and synthesization boards out there, and I could use them to do something really fancy (like audio control of the chair - "To the bathroom!"). Also, with both visual and audio components to the Stamps I could begin to give the chair some AI of it's own, thus having an intelligent mobile desk chair. That would be cool.

So I just thought I'd post my thoughts so far on what's happening in phase two. I'm really looking forward to this. It's going to be a lot less grudge work than getting the chair to work is.

I've been thinking about what to do next with the chair, and one idea that keeps on sticking in my mind is developing a head-mounted system (like on a helmet) with cameras and stuff like that so that the driver gets some sort of mediated-reality experience or something like that. The chair could also assist with various things - I don't know what yet - if it can see what the driver sees. I got this idea because I have been checking out the CMUCam from Parallax. It's a very neat little camera, with 'blob' tracking and lots of other really interesting functions. That, in addition to a regular CCD camera, mounted on a helmet, with a viewfinder that the driver sees everything through, would be really awesome. Nothing's set in stone yet, but I think that would be a very interesting path to take with the chair as soon as it can move.