Prototyping a Demo

This weekend we will be at the Parallax Robot Expo.  While Lon has already got a bunch of cool robot demos together, we will also be showcasing a big internal R&D project we have been working on:  a solar tracker.  We have the first pass mechanics done and I am responsible for the control electronics for the system.  For the demo, we will not be actually tracking the sun, instead a user will be able to “drive” the tracker using either dials or a keypad interface.  The cool thing about the initial electronics prototyping is that all of the “hard” stuff (motor control, user interface, etc) was made relatively easy with off the shelf components.

The rotation of the tracker is driven by a slew-drive motor from Kinematics Manufacturing.  The tilt of the tracker is driven with a linear actuator from Firgelli Automations.  The slewing drive runs at +24V and the linear actuator runs at +12V.  Because they are both highly geared they take less than 1A to move a large load.   The slew drive has quadrature encoder feedback, while the linear actuator has an analog potentiometer feedback.  With these basic requirements in hand I could start fleshing out the design.

Each of the motors can be controlled with a Synaptron micro single-axis motor controller.  The Synaptron micro has the power capability to drive the motors and functionality to interface directly to the different feedback mechanisms.  To make a demo, I needed an interface and some brains for the system.  For the brains I used an Arduino Uno; for the display a 2X16 serial display from Parallax; and a MEMKEY for user input.  To interface the Synaptron micros to the Arduino I used a Synaptron Micro Test Board for one and a Synaptron Micro Arduino Shield (AN2009).

From there, I was able to wire everything together in a big rat’s nest, as shown in the picture.  I wrote some code to control everything and now have a basic demo with all of the components shaken out.  For the show, I will put everything in a box to clean it up and make it a bit more robust. 

The next steps for the actual Solar Tracker are to specify the actual desired operation, move everything to a custom PCB, and write the real tracking software.  More on this in the next few weeks and months.

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