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Motors & Sensors Setup 
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Joined: Sat Mar 19, 2011 2:32 am
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Post Motors & Sensors Setup
Which motor do you select in the Motors & Sensors Setup if you have a 393 high torque Y'd to a 296 for say the arm tower? Will selecting the wrong motor type create any bugs somewhere in your code? Also what does checking the Encoder box on that same screen do? Is it referring to the quadrature encoders or the IME encoders? Does it do anything other than notating it in the #pragma at the beginning of your code? Thanks. :?


Tue Aug 14, 2012 4:44 am
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Post Re: Motors & Sensors Setup
jokai wrote:
Which motor do you select in the Motors & Sensors Setup if you have a 393 high torque Y'd to a 296 for say the arm tower? Will selecting the wrong motor type create any bugs somewhere in your code? Also what does checking the Encoder box on that same screen do? Is it referring to the quadrature encoders or the IME encoders? Does it do anything other than notating it in the #pragma at the beginning of your code? Thanks. :?


Hello jokai,

When you say you have the motors Y'd together, do you mean you are running a cable splitter from one port to two motors? If so, I'd be a bit careful; running more than one motor from a port can create a higher current load on the fuses inside the Cortex (which can cause it to trip if overheated). Also, if you have two motors spliced into one port, it will send the same signal to both of them at the same time; so as you rotate one motor, the other will rotate as well.

Generally with Y splitters we recommend running two of the same motors for this very reason; you don't have to select in the code between the two. Since both are using the same PWM for speed control and the same voltage levels, you can safely pick either one in the Motors and Sensors setup window HOWEVER the selection ties the motors to specific encoders, which brings me to my next point.

The encoder box tells the microcontroller that there is a shaft encoder in use and which port it is in. If you plan on using encoders on both of your motors, you will want to give each motor its own port on the microcontroller and tie each one to an encoder in ROBOTC. You can select either quadrature encoder or I2C (IME) encoders and tell ROBOTC which port it is plugged into.

There is actually a good post on splitting the two motors on the VEX forums you might want to check out: http://www.vexforum.com/showthread.php?t=33472
We also have a informative programming guide for the IME's on our wiki: http://www.robotc.net/wiki/Tutorials/Pr ... er_Modules

Let us know if you have any other questions!

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Mon Aug 20, 2012 12:42 pm
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Joined: Sat Mar 19, 2011 2:32 am
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Post Re: Motors & Sensors Setup
John, we actually have a 3 wire motor (not 269, my error) and a 393 motor set for torque connected by a Y cable to one motor port on each side of our arm towers. In our own "fuzzy" logic, we figured having them Y'd would ensure that they were getting the same power. We haven't had any problems yet & the link you referred me to had team 254 saying that would be ok. However, we did not realize what you said about drawing more power that way. The rationale behind using the 3 wire motor was to avoid using 10 393 motors so we wouldn't trip any PTCs. We currently are using 8 393 motors else where with 2 3 wire motors on the arm towers geared together with a 393 motor. Which alternative would be safer, using 10 393 motors or 8 393 motors with 2 3 wire motors, as far as drawing too much current & tripping the PTCs?

Also, regarding the IMEs since they do not have 2 wires that you can interchange like the quad shaft encoders, how does it know which way is positive & which way is negative? Thanks for the help. joan


Sun Sep 30, 2012 11:21 pm
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Post Re: Motors & Sensors Setup
John, if it is better to use separate ports for each motor, I had read somewhere to avoid using ports 1 & 10 if possible. Would it be okay to use say port 1 & port 2 for the 2 motors geared together driving one side of the arm towers or is there a slight difference? Thanks.


Mon Oct 01, 2012 1:22 am
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Post Re: Motors & Sensors Setup
In my experience, avoiding tripping the PTC's isn't just about a combination of 8 393 motors vs 10. It really comes down to how much you're stalling the motors when you're lifting objects or pushing up against other robots. Imperfections in drivetrains, heavy robots, and high strain contribute as much or more than the number of motors used.

Based on your choice in the Motors and Sensors Setup, ROBOTC has a default direction for the IME's (positive or negative). A point of reference for positive would be if the motor was plugged into Ports 1 and 10 such that it was correctly plugged in according to the key/slot. The rest of the motors would plug in/connect to the Motor Controller 29's in the same direction.

There should be no problem in using Motor Ports 1 or 10.

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Mon Oct 01, 2012 2:23 pm
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