TB6612FNG Motor Control Board

Background

As part of a to-be-announced project I am working on, I ended up designing a new Toshiba TB6621FNG motor control board which is designed to be compatible with the Raspberry Pi. Before I began this design, the lab I am working in had been using controllers based on the Rohm BD6222HFP chip. This is a chip which is well suited to hefty 12V designs. However, we now need something more efficient and less expensive. The TB6612FNG chip is:

    • Less expensive (by ~$1 at single unit scale)
    • Requires more hobbyist friendly supply voltages ( 3-5.5V instead of 6-18V)
    • Provides similar output amperage compared to the Rohm chip.
    • Input current in standby (IIH) averages 35μA less.

    All this lead me to design around the new chip. Of course, breakouts from the usual suspects such as Sparkfun (seen here) and Adafruit (seen here) are available. Adafruit even provides an advanced version which is (in my opinion) over-specialized (see it here). So why did I reinvent the wheel in this case? Because the basic breakout boards are too limited and the advanced version is too limiting.

    Pi Woes

    The GPIO pins on the Raspberry Pi are a wonderful thing. They provide so much room for innovation. However, when you only need one or two specific pins, and those pins are scattered all over the GPIO, it is inconvenient and slightly expensive to design a board with the full 26 pin socket. Instead, selective use of 3-pin servo headers can be used at lower cost. The TB6612FNG motor control board I designed uses this type of design.

    Additionally, there is a problem unique to certain pins of our good ol’ GPIO friend. During boot, pins are not consistently pulled up or down. This can mean that a motor run by these pins may do strange things during boot. If one of those motors is controlling some sort expensive optics as in my case, this is to be avoided. There are a few work around options for this. It is possible to set up a cron job at boot which will set all of the pins to pull up or down, but this may be a challenge to a user with less bash experience. For my project, I need something that allows a user to run the device without worrying about the details. So I implemented a hardware solution. The GPIO pins are pulled down by 100k resistors on my TB6612FNG motor control board.

    An advanced setting was made available to divorce the chip ground from the motor power ground by way of a solder jumper.

    Schematics

    Pictured below is the schematic for my TB6612FNG motor control board. The project was designed with KiCAD.

    TB6612FNG motor control board schematics

    The picture below shows the layout of the board, omitting the back copper plane. I was able to fit all of the traces on one side of the board, so the B.Cu layer is mostly ground plane thermal relief.

    TB6612FNG motor control board copper layout

    Next week, I will show how I made the board.

Dissertation: Development and Applications of Chemical Sensors for the Detection of Atmospheric Carbon Dioxide and Methane

It is a new year, and my dissertation has finally made it past embargoes to publication. Allow me to present: Development and Applications of Chemical Sensors for the Detection of Atmospheric Carbon Dioxide and Methane. You can view the ProQuest entry here. There is a download link to the full text at the bottom of this entry.

Title

Development and Applications of Chemical Sensors for the Detection of Atmospheric Carbon Dioxide and Methane

Abstract

This is a description of the design of a low-power, low-cost networked array of sensors for the remote monitoring of carbon dioxide and methane. The goal was to create a scalable self-powered two-dimensional array for the detection of these gases in a large area. The sensor selection, electronic design, and data communication was studied and optimized to allow for multiple units to form a self-assembling network for acre-scale coverage with minimal human intervention. The final electronic design of the solar-powered units is flexible, providing a foundation for future field deployable remote monitoring devices. Sensors were selected for this application from commercially available models based on low-power, low-cost, market availability, detection range, and accuracy around the global baseline criteria. For environmental monitoring, carbon dioxide sensors are characterized near 400 ppm and methane from 2 to 200 ppm. For both gases, exertions up to several 1000 pm were examined to mimic large releases. An Xbee mesh network of radios was utilized to coordinate the individual units in the array, and the data was transferred in real-time over the cellular network to a dedicated server. The system was tested at a site north of the Oklahoma State campus, an unmanned airfield east of Stillwater, OK, and an injection well near Farnsworth, TX. Data collected from the Stillwater test sites show that the system is reliable for baseline gas levels. The gas injection well site was monitored as a potential source of carbon dioxide and methane leaks due to the carbon dioxide injection process undertaken there for carbon sequestration and enhanced oil recovery efforts. The sensors are shown to be effective at detecting gas concentration at the sites and few possible leak events are detected.

Reference Information

Subject Classification 0485: Chemistry
0486: Analytical chemistry
0494: Physical chemistry
Identifier / keyword Pure sciences
Carbon dioxide
Detection
Enhanced oil recovery
Methane
Remote monitoring
Sensing
Author Honeycutt, Wesley T.
Number of pages 196
Publication year 2017
Degree date 2017
ISBN 9780355396188
Dissertation/thesis number 10276467
ProQuest document ID 1965485293
Advisor Materer, Nicholas F.
Committee members Apblett, Allen W.
Fennell, Christopher J.
Ley, M. Tyler
White, Jeffrey L.
University/institution Oklahoma State University
Department Chemistry
University location United States — Oklahoma
Degree Ph.D.

Download

Here is a download link to the complete dissertation file: Dissertation.pdf

NOTE: This file is a 166.7MB PDF document. Since I am not a rich man, my website is hosted on a slow, inexpensive server. This download may take some time. It may be quicker to download from a library site, but I want to make sure the document is available to everyone.