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Comments by Patrick
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Electrical characteristics of servos and introduction to the servo control interface
- 29 January 2020Hello, John.
Unfortunately, the comments for this blog post are not a good setting for troubleshooting like this. Instead, you might consider making a post on our forum:
https://forum.pololu.com/
However, it sounds like you might not be using any of our products. If that is the case then the help we can offer is probably limited, so you might have better luck posting to a hobby RC focused forum.
- Patrick
New product: G2 High-Power Motor Driver 24v13
- 27 January 2020Hello, Gary.
As Claire commented before, we do not release the schematic or components for these drivers, but we only expect the built-in current sensing on these drivers to be less precise at low currents. If you have an application where you need more precision, or where you expect to regularly need low-current measurements, then you might consider using an external current sensor like one of these:
https://www.pololu.com/category/118/current-sensors
The schematics and datasheets for the current sensors can be found under the "Resources" tab of their product pages.
- Patrick
New 5V step-up/step-down voltage regulator S9V11F5
- 14 January 2020Hello.
Performance-wise, the S9V11F5 is superior to the S7V7F5. Because it has components on both sides of the PCB, The S9V11F5 might be a tighter fit on the DRV8835 Dual Motor Driver if you plan on mounting it the same way shown on the driver's product page, but it should still be okay as long as you are paying attention to that when you are soldering.
- Patrick
Video: Setting the Current Limit on Pololu Stepper Motor Driver Carriers
- 6 January 2020Hello, Mike.
The current limit setting is one factor that will affect the maximum speed you can get out of your stepper motor, so to maximize that you should make set the current limit to the maximum allowed by your stepper motor or stepper motor driver, whichever is lower. You can also check out this forum post which lists some other things you can do to maximize the speed you can achieve with your stepper motor:
https://forum.pololu.com/t/increasing-the-speed-of-a-stepper-motor-using-the-a4988-and/5135/3
- Patrick
New adjustable voltage regulators with multi-turn fine adjustment
- 30 December 2019Hello, Simon.
Please refer to the "Setting the cutoff voltage" section of the product page, which answers both of your questions.
- Patrick
37D gearmotors: helical pinion gear, new 150:1 gear ratio, and performance graphs
- 21 October 2019Hello.
The inductance of our 37D Metal Gearmotors is about 2.3 mH.
You can estimate a motor's electrical resistance by dividing its rated voltage (12 V for the 37D motors) by the stall current (5.5 A for the 37D motors). So for the 37D motors, that gives you a value of about 2.2 Ω.
We have not characterized the rotor inertia for our motors yet, but you could approximate something for that by determining the moment of inertia for the output shaft. The shaft is made of stainless steel and its dimensions can be found in the dimension diagram (which can be found on any 37D motor's product page under the resources tab):
https://www.pololu.com/file/0J1704/37d-metal-gearmotors-dimension-diagram.pdf
By the way, I would expect the rotor inertia to become negligible once anything of substantial inertia is attached to your motor or once your motor is loaded in a real application.
You can determine a motor's viscous friction constant by dividing the no-load current by the no-load speed and then multiplying by the motor torque constant. The motor torque constant is the inverse of the inverse of the slope of the current-versus-torque line in the performance graphs.
- Patrick