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For my last part of this road test I'm looking at the stall guard function. This works by sensing the current through the motor coils so my first step was to look at the datasheet chapter 9 on sense resistors. Thanks to jancumps for reviewing the schematic earlier in the roadtest and identifying that the evaluation board uses a 0.06Ω resistor. Note that there are two sense resistors, one for each of the motor coils. The motor current can then be determined with the following calculation ...
The next test for the TMC5161 was positional accuracy. This is where my test rig came in. I fixed the motor to one bracket and attached the 3D printed drum. A waxed cotton thread was wrapped around the drum twice for grip and then fed around the idler at the far end of the test rig. The tension was provided with some rubber bands. Finally a card was added in the middle of the rig and the cord was marked with white paint. This time the position mode in the TMCL-IDE was used along with the pos ...
To test the accuracy of the stepper driver I am using a large test rig with a pointer to indicate the position. There is also an optical encoder mounted on the back of the stepper motor and the TMC5161 chip can read the pulses from this and make it's own conclusions about missed steps. So thought it would be good to wire up the encoder and see how it behaves.   Wiring the encoder  From the datasheet ABN Incremental Encoder Interface The TMC5161 is equipped with an incremental encoder ...
Before committing to my tests I thought I'd make sure I could make the motor turn. I wired up the motor and trio of boards. The screws were quite small so I had to use a jewellers driver. I connected up the power supply, set it to 9v with a 0.5A limit.   I fired up the IDE and it immediately reported the there was old firmware on the Eval board. I took the attitude of "what's the worst that can happen" and clicked on the Firmware update button. This asked me to select a file and I had a lo ...
Plan My road test of the TMC5161-EVAL-KIT by Trinamic is two fold. Firstly to confirm that the setup can accurately and repeatedly step to the required position. Secondly to look at the setup under stall conditions.   Accurate Stepping To measure accurate stepping the stepper motor will be used to raise a weight on a string. The position of the weight will be recorded and a sequence of steps run to move the weight up and down and to confirm it returns to the desired locations. This can be r ...
To some extent gloves are a harder challenge for a capacitive sensor than thick front panels as the sensor can't be calibrated up front for a specific pair of gloves. For my testing I picked 3 different gloves. The first are heavy duty PVC, the kind you might use when handling chemicals, the middle glove is a welding gauntlet with cotton lining and finally the last glove is a thin leather, typically used for TIG welding. The board boots into it's default configuration the settings I'd been us ...
The next part of my roadtest with the CapTIvate sensors is to see how they perform with different front panel materials. If you think of the basics a capacitor is two conductors separated by an insulator. If we put in thick insulator with different dialectric properties to air then we are going to have a significant effect on the sensor. I picked two thicker challenging materials and one that I might consider for a front panel.   The materials I had to hand were:   6mm Toughened Glas ...
As mentioned at the end of part 2, I've installed Code Composer Studio so that I can upload new code to the development board. following the workshop guide the first step is to generate some code from design studio and import it into CCS. This works fine as long as you don't generate your code into the CCS workstation folder as it will be making a copy of it there. You can then "Debug" the code to compile and upload it. This may take a few moments the first time as there are some libraries to ...
To use the development kit you need to download and install the "CapTIvate™ Design Center" GUI   CapTIvate_Design_Center 1_20_00_01 - TI.com   This allows you to see the outputs from the sensors and design new interfaces. The installation is very straightforward and simply requires you to confirm the license and select and installation directory.   The designer includes the samples mentioned in the getting started tutorials and these in turn contain handy annotations. & ...
MSP CapTIvate™ MCU Development Kit from TI   First impressions of this kit is that it exudes quality. A sturdy cardboard box is lined with high quality foam inserts. Each of the boards is wrapped in an anti-static bag, there are 6 in total. The boards are high quality too with small rubber feet, high spec connectors and a gloss black finish that would not be out of place on a top end stereo.   The boards in the kit are: the main MCU board, a programming adaptor, isolation boa ...
For me one of the nice features of the MBR3 chips is the I2C bus. This allows you to read the status of the switches from a microcontroller with just two wires. If you can spare a 3rd wire then you can also use the "host interrupt" feature to tell the microcontroller when something has changed with the state of the switches. This means that you can have a selection of debounced switches with status LEDs with the minimal of wiring and coding. The I2C bus can even be used to program the chip using ...
For my road test of the CapSense MBR3 I want to see how suitable these sensors are for a workshop environment. In my previous test I looked at different types of gloves, so for this test I am going to review different front panel materials and thicknesses. When I looked at what materials I had in the workshop I found the following: 2mm clear polystyrene 3mm polycarbonate 3mm acrylic 10mm acrylic I also found some toughened glass around the house in the form of a bathroom shelf 6mm and sc ...
For my road test of the CapSense MBR3 I want to see how suitable these sensors are for a workshop environment. For that reason I'm conducting two key tests. Firstly one using different types of gloves, and secondly one with different thicknesses of front panel.   Although I don't wear gloves for most of my workshop activity they are essential when welding or working with chemicals.   I configured the board so that each of the switches had a different sensitivity, the threshold was se ...
As mentioned in my previous post CapSense Evaluation Kit - First Impressions, I planned to run through the user guide to familiarise myself with the board. I was particularly interested in understanding the configuration of the switch sensitivity and the SmartSense auto-tuning feature. I'd effectively run through parts 1 and 2 already so I returned at section 3 Kit Operation. I ran through the setup instructions 3.1 - 3.3 with no issues.   It's worth mentioning the kit features:   Fo ...
I volunteered for this road test because I thought that capacitive switches could be a good solution for front panels for CNC or measuring equipment in a workshop environment. I particularly liked the idea that you could design your switches on a PCB and then connect to a microcontroller via I2C with things like debouncing and calibration handled by the MBR3 chip. Alternativelty the GPO pins can be configured using to provide signals directly. This also means less wiring and no mechanical parts ...

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