Articulated Wheel

articulated_wheel

We’re messing around with the design and control of an articulated robot wheel.  We’re not even sure at this point what the end goal is, but initially we’ll be using Synaptron Micro motion controllers to control a multi-jointed wheel system.  This first bit of hardware is just designed to test weight limits and motion profiles.  In the end it would be nice to have a walking wheeled systems.  In the end we’ll have to do some more in-depth mechanical design to handle allowed movement ranges, weight limits, and wiring requirements, but for now this setup will be fun to flail around a bit.

Round 2 Goes To The Electrons

synaptron_mega_round2

Our never-ending quest to develop a powerful but tiny motion controller for DC motors continues.  In my second hardware iteration of the Synaptron Mega design I was flummoxed, flustered, flabbergasted, and then finally forged forward.  But the electrons gave me a run for the money on this one.

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Proportional Motor Control In A Microcontroller

pgain

Proportional motor control is useful in many applications.  Control theory describes

proportional control as…

Pout = Kp*error( t )

Where Pout is your drive signal, Kp is your proportional gain, and error( t ) is the error signal.  Here’s an example of how this translates to a microcontroller application that isn’t using floating point numbers.

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Mega-tronics

synapmega

A few weeks ago I began the process of re-designing our Syanptron Mega prototype.  This is a motion control module based on the Synaptron Micro product we currently sell.  The idea was to come up with something a little more powerful, but utilizing the same operating system.  We were also trying to keep the cost down, which in this case means frugal use of components and small size.

There’s kind an interesting backstory to this design.  We make another product called the Motion Mind 3, which is obviously in its 3rd iteration.  The Motion Mind 2 was a design I really liked, and not something I was keen on replacing.  However, we had supply issues with two key Infineon parts on the Motion Mind 2.  At the same time we had a  customer who wanted to use the Motion Mind 2 in an application but required that it be ROHS compliant (basically lead free).  The Infineon parts were not compliant.

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solar tracker fabrication

In a previous post, I started rambling on about the basic design of a scaled solar tracker we were building as a demonstration.  The Google Sketchup design ended up something like this…

solar tracker 4

Since mechanical fabrication is not our specialty, we cheated a bit and printed scaled “cut-outs” of various pieces to cut and drill.  Using SketchUp to do this saved quite a bit of time determining hole and edge layout during fabrication.

Here is a picture of the slewing drive used to rotate the panels.

slew drive

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Once more into the breach – Synaptron Mega

SMrev2

Work on the Synaptron Mega, based on our Synaptron Micro design, is moving forward.   You can see the first prototype in the post Synaptron Mega Enters Development Phase.   My initial tests focused on basic functionality and firmware modifications. The prototype performed well.  With minor hardware modifications I think we could have moved forward with a production version, but I felt a strong desire to make changes before completing my tests.  The image above is a first attempt at board layout for the changes, and is probably pretty close to actual size.  The pin-to-pin connections have not been made, and that constitutes another 4-8 hours of work.

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Joustbot– hit the brakes on skid steering

rcradios

I guess this is step 6 of the Joustbot epic assembly adventure.  At the end of step 5 I was waiting for some 9.6V batteries to arrive and was a little concerned about how the 12V motors would behave at less than 12V.  It turns out that that they run just fine, and the robots are fun to drive at this lower voltage.  Unfortunately, I did run into a problem that scuttled my grand plans of finishing this project last Friday.

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Synaptron Mega enters development phase

synaptron_mega

A couple of weeks ago I built the first prototype of our Synaptron Mega (the board with the red glow in the photo).  This is our Synaptron Micro operating system with a larger H-bridge.   The operating system is designed to run on Microchip’s dsPIC33FJ64MC802, and creates a very versatile and programmable motion controller.  It is designed to control brushed DC motors.

I hadn’t had a chance to test the board until this week. By the time I did get around to testing it there were problems.   Not “flame-on” kind of problems, but certainly things I wasn’t expecting.  First, every time I ran the microcontroller debugger the code would freeze.  This caused me to spend a  couple of hours troubleshooting the firmware.  It turns out I had missed changing a couple of settings related to the H-bridge drive signals, and was creating a shoot-through condition whenever the PWM output was turned on.  Shoot-through is when both the upper and lower side of H-bridge leg are turned on. Once that was sorted out, things started to go pretty smoothly.  The shoot-through actually turned out to be a blessing in disguise since it was essentially testing a short circuit.  The H-bridge  limited the load current to 11A, and after a second or two thermal shutdown reduced that to 1.5A.  No traces or surrounding components were lost.  It was kind of a nice upside to wasting time troubleshooting.

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Microchip’s MTS2916A Stepper Motor Controller

Microchip is carrying the MTS2916A stepper motor controller (or dual DC motor controller). I’ve run across this part before, but at the time it was sold by Allegro, and at a much higher price. Microchip’s budgetary pricing is $0.80US for 1000 unit quantities, and it can be purchased in small quantities from MicrochipDirect.com.

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