Velocity control with the Synaptron Micro

I spent a couple of days adding velocity control to our Synaptron Micro motion controller.  I should probably be more clear.  The product already has the ability to use the velocity measurement from a quadrature encoder as a feedback source.  Meaning you can operate a motor at a PID controlled velocity.  What you couldn’t do was operate as a position controller with a velocity limit applied to the movement.  Okay you could already do that too, but the methods were a little “complicated”.  The desire for a less complicated velocity control method  came about when working on the articulated robot wheel.   Laziness, the mother of invention.

For those not familiar with the Synaptron Micro the product is configured by modifying internal register settings.  For some applications, such as analog control of position, you only need to configure the device once.  For other modes such as serial control of position it is assumed you have a controller that is continuously in contact with the Synaptron Micro motion controller.

The video above shows the results of the velocity control that was added, while the remainder of this blog entry covers other methods of controlling motor speed during movement.  Here are the four ways you can now control a motor’s velocity while moving to a position…
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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


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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Using Radio Control Transmitters for Motor Control


Sometimes its useful to be able to control a motor’s speed or position with a radio controlled signal.  RC (car, airplane, boat) radio transmitter and receivers are readily available and relatively inexpensive. For example, I just picked up a 2.4GHz spread spectrum transmitter and receiver for about $60.  To use these devices with standard DC motors you just need to do a little numerical/hardware conversion.

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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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The Beginnings of a Solar Tracker

A while back, we were looking for a way of of demonstrating the capabilities of our new line of Synaptron motor controllers, and came up with the idea of building a scaled version of a solar tracker.  The two motors controlling azimuth and elevation would be controlled by a pair of Synaptron Micros.

After a bit of research, we decided to use a small slewing drive from Kinematics for rotation and a linear actuator from Firgelli Automation to adjust the tilt of the panels.  Slewing drives, and more specifically, slewing bearings are really interesting, as they are able to withstand large loads in both a radial and axial direction.  Much larger versions are used on cranes and excavators.

Next, we used Google SketchUp to come up with a basic drawing of the head unit.  Here’s a pic of the original design, sans the linear actuator.


solar tracker 4

The bottom unit is the slewing drive and is able to turn the entire mechanism, as well as stand up to heavy winds and torque loads.

The linear actuator (not shown) will connect at the end of the two arms and be able to adjust the top mounting bracket between 0 and 90 degrees.

Of course then we had to actually build it…  More on that later.

Solar Tracker Electronics Demo–Done (kinda)

We’ve been working on a solar tracker demo for the Parallax Robotics Expo.  As the expo starts today, we needed to get something finished yesterday.  We did get something finished.

It is a first pass demo to get our feet wet in this area.  We needed to hone-in our mechanical design abilities (we will have a few blog posts on that coming up) and I needed to use with the Synaptron Micro in  a full-sized demo.  I was able to get the previous rat’s nest prototype into an enclosure with a rudimentary user interface.   There were some last minute snafus – there always are – made tIMG_0407he more nerve-wracking because of the deadline pressure.  However, we now have a functioning demo, that expo guests can “drive”.

For the demo, you can drive the rotation and the lift of the solar panels in either analog mode (controlled directly with the Synaptron micros) or in serial mode (communication coming from an Arduino Uno).  The user is able to use the analog mode with the two silver-dialed potentiometers shown on the box.  For serial mode, the keypad is used.  The LCD and and LED combinations show the user what mode and what condition the solar panel is in.  All in all a pretty straight-forward approach to show-casing the Synaptron Micro’s capabilities.

So why is the demo “kinda” done?  As mentioned previously, this was just to get our feet wet.  Now that we see it can be done, we want to kick the demo up a notch.   Already we know that we want:

  • – A custom PCB
  • – A better case to display the Synaptron Micros while in operation
  • – An integrated power supply
  • – Better connections to the two motors
  • – Actual solar tracking (by date, location, and sensors)
  • – Absolute position tracking for the rotation, not just relative
  • – A bigger/better display to show off what is actually happening
  • – Professional looking graphics

We will also get some good feedback from the attendees of the the expo, so we should be able to add to the starter list.  Keep an eye out for more changes down the road.  See you at the expo.

Once more into the breach – Synaptron Mega


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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