Kuba Blog 5 - Motor Control

 Blog 5 - Motor Control

Introduction:

This week was concerned with getting the motors on the Swarm bots moving, using PWM signals sent from the PIC to the motor controller. This blog will outline the problems encountered, the connections made to get the motors to work, as well as videos and scope readings of the motors working.


Procedures:

Last week we investigated the PWM outputs from the PIC and verified their correctness. This meant that we know the signals were correct, so getting the motors working was a matter of setting the motor controller into its correct mode, and wiring everything correctly. First we decided to wire everything correctly. There is really only two main things we had to wire, i.e. the two PWM outputs from the PIC to the motor controller. The figure below from the Sabertooth 2x12 motor controller's datasheet shows the wiring of the two inputs. 



The way the bot was given to us this wiring was done incorrectly and left an open circuit, so we wired it up correctly and then connect the two PWM outputs from the PIC to these inputs. We used an oscilloscope to test which pins output the PWM signals. Once this was done we had to figure out the correct settings for the motor controller. The controller uses 6 switches to change certain aspects of its behaviour. Initially we saw an item in the datasheet that implied PWM inputs are used in analog mode, one of the three main operating modes, the others being R/C and Simplified Serial. This later turned out to be an incorrect assumption and somewhat a lack of clarity on the part of the datasheet. We later discovered that while R/C mode is mainly used for being controlled by a radio receiver, it also includes microcontroller mode. The figure from the datasheet below shows that setting switch 1 down and switch 2 up puts the controller into R/C mode.



Once this was done we had to decide how to set switch 3. The figure below shows the behaviour associated with switch 3.


Switch 3 essentially tells the controller what it is getting it's power from. In our case we set it to the up position since we aren't using lithium cells. Switch 4 has the same control regardless of mode. Essentially when it is up one input controls whether the motors are going forward or backward, and the other controls turning. When it is down each motor is controlled independently by the two different inputs, which is what we want so we put it down.

Switch 5 is also universal among modes, and it selects the response of the controller, choosing between a linear and exponential response:


Since we wanted a linear response we decided to set switch 5 to the up position. Finally, in R/C mode switch 6 decides between two modes within R/C mode. If the switch is up then we are in standard R/C mode, but when the switch is down the microcontroller goes to microcontroller mode and expects PWMs as input, as we want so that's what we set it to:


Results:

Finally, after some trial and error, and consulting the sometimes confusing datasheet, the correct switch positions were chosen. We programmed the PIC with the example PWM SM code from Jason, modifying one of the invalid PWM outputs (0.5ms) to a valid one. 

Comments

Post a Comment

Popular posts from this blog

 Hello All, Welcome to bin bot, Your first blog entry should contain the following, 1.0 Picture of yourself and some interesting background info 2.0 take about the an interesting post from one of the previous blogs..what you liked about it!!! 3.0 the Binbot see videos below, Have athink about cool stuff you think we could do with the bin bot..share videos idesa pictures 4.0 state machine diagrams the best thing ever !! history, your drawio diagram cool example projects that used state machines diagrams eg mars rover "good night oppy" good luck
Read more

Blog 1 - Igor Kapusniak

Image
Blog 1 - Igor Kapusniak    About Me My name is Igor Kapusniak, I am currently in my 4th year of studying Applied Computing in S.E.T.U. with a specialisation in Internet of Things and Automotive. My hobbies include running, 3d modelling and 3d printing, and reading books on astronomy/physics.      Bin Bot Project Ideas  Fullness Tracking Track how full the Bin Bot is using ultrasonic sensors and display the information on a dashboard. Audio from the microbit could play when certain fullness thresholds are reached. This could also include automatic notifications when the bin is ready to be emptied. Remote Control Control the Bin Bot remotely from any where using microbits, MQTT, and a dashboard. The Bin Bot could be made to look in a specific direction and make a facial expression using its eyebrows. Text to Speech Implement a text to speech system that allows the Bin Bot to give audio updates or warnings. For example, it could say: I’m almost full, Thank...
Read more

Blog 5 - Bin Bot Project - Davin Barron

Image
 Blog 5 - Bin Bot Project - Davin Barron Introduction The core objective of the Bin Bot project is to develop an intelligent, automated smart bin utilising an MQTT network. During the initial design phases, our primary focus was simply identifying what smart features were technically viable, practical to implement, and well-aligned with the bin's overall functionality. Following plenty of collaborative team discussions, we decided to center Bin Bot around Ireland's deposit return scheme, specifically tailoring the user experience for primary school classrooms. By gamifying the recycling process, our goal is to teach children the vital importance of sustainability through a fun, engaging, and interactive activity. Now that we are in the final sprint, we can really see how the Bin Bot's IoT capabilities are starting to take root and the entire system is finally taking shape. In this blog, I’m going to talk about my specific technical contributions to the project, as well as m...
Read more