There has been many developments of Arduino based motor controller boards and shields. They work great with most low power motors but when you need to do more serious motor driven project, then you find that most of those shields aren’t capable to drive bigger motors. Arc Robotics decided to change situation by offering affordable 43Amp Arduino motor shield.
They are running kickstarter campaign. They designed controller to be flexible, powerful and easy to use. Arc-Controller can run as standalone motor driver because there is an Atmega328 Arduino compatible microcontroller. Controller can also be attached to another Arduino or other board as slave device and accept commands. It is able to drive single stepper motor up to 43Amps or couple DC motors. Controller has all necessary fail-safes installed like reverse polarity, over temperature and over current protection. Seems to be great choice if you seriously thing diving in to robotics.
One day Davide found that his pool cleaning robot was dead. Damage was caused by chlorine which cut through gasket and shorted circuits. Official repairing wasn’t an option because new electronics would cost more than robot itself. So he thought that in reality cleaning robot doesn’t do much – moves around and sucks water through the filter. He can build his own control circuit based on his microcontroller of choice.
He built a circuit which is actually a count down timer. Robot works in periods that can be selected with five buttons. Settings are stored in to microcontrollers internal EEPROM so once set it always works as programmed. Status LEDs indicate robot working conditions. Green shows that robot is working, while RED indicates over/under current detection. Robot moving motor is BLDC, so he used hobby ESC Mistery FM30A to drive motor with PWM generated from Atmega. That’s it solved and robot continues its work.
Hobbyists love Linux powered development boards, because they give lots of flexibility, network connectivity and other benefits OS can give. Linux driven development boards are great, because they already have I/O pins to interface physical world and build project at different level. Market already have over dozen great Linux-based development boards and sometimes you may get stuck thinking which is best to start with. We all are familiar with Raspberry Pi, but don’t get excited, and think your needs first before purchase.
Tony Dicola, recently have made a comparison of four common Linux-based development boards: Arduino Yun, Beaglebone Black, Intel Galileo and Raspberry pi. He listed most of their parameters in to table so you could clearly compare them side by side. Then he takes to next part – performance test. He runs nbench tool, which was developed to measure performance of Pentium class computers. It is obvious even from parameter list that Beaglebone black and Raspberry Pi takes leading positions. Also he measures power usage when idling and running benchmark Raspberry Pi model A leads by maxing at 150mA. While Intel Galileo stands between 500 – 600mA. Other test include CPU temperature measurement, where Raspberry Pi shows best results and Galileo worst. Hardware is worthless without software support and tools, Tony goes through available packages, and support. After comparison it is always hard to tell which one is generally best. Each board brings some value to the bucket. For instance Arduino Yun is great for Arduino compatibility and WiFi, Raspbery Pi is great for learning Linux as it has large community and is cheapest board from the list. Beagle bone gives more I/O and gives more real-time control.
Programmable dummy load is great device for testing power supplies, batteries. It is up to you how you want to set load behave – like constant resistance or constant current or constant power. Wigman27 wrote extensive instructable on how he built his own version of dummy load. He used sandard technique that is used in most cases – MOSFET act as variable resistor controlled through op amp. Microcontroller takes care of reading and setting voltages to sustain selected level.
Current flow is controlled with BUK954R8 – 60E MOSFET. MOSFET gate is driven by LM324 Op-Amp which accepts DAC (MCP4922) control voltage. Microcontroller reads sense voltage from MCP3204 ADC. There is also a temperature sensor on heatsink which keeps an eye and turns fan if things get hot. Key parameters of load are:
max Voltage input – 24V;
max load current – 8A;
max dissipated power – 50W;
min load current – 15mA;
load current error – 3mA.
Project explanation is really great even for novice. If you are not going to built power load, then material may serve as refreshing course of basic electronics.