[FTC]: Encoders on new Andymark motors.

[CougarRobot]

Interfacing the new AndyMark NeveRest Motor with the HiTechnic Motor Controller

We have tested the new AndyMark NeveRest Motor and it works well with the TETRIX/HiTechnic Motor Controller. Here's what you should expect and what you need to do to make it work the way you want on an FTC robot. We will use motorD as our motor in our examples.

First we need to agree on some terminology. The TETRIX shaft encoder used with the TETRIX motors is a US Digital e4P with a 360 degree encoder wheel. Model E4P-360-236-N-D-H-D-B. To use US Digital's terminology it produces 360 Cycles Per Rotation (CPR) or 1440 Pulses Per Rotation (PPR). It is a quadrature encoder producing 4 Pulses per Cycle. In FTC use, with ROBOTC, it will produce 1440 PPR, ticks, or a count of 1440 in nMotorEncoder[motorD] per revolution.

The AndyMark NeveRest motor's built in encoder produces 280 cycles per revolution (CPR). We tested it. As expected with 280 CPR, it outputs 1120 PPR, ticks, or a count of 1120 in nMotorEncoder[motorD] per revolution.

So, here's the only tricky bit. The NeveRest motor’s 1120 PPR is only approximately 78% of the TETRIX Motor’s 1440 PPR. You need to adjust your range when running under PIDControl from 0-100 down to 0-78.

The HiTechnic motor controller expects 1440 PPR and is "tuned" to drive a Tetrix motor at about 150 rpm when using PIDControl and a commanded speed of 100% motor[motorD]=100;. That is, the motor controller will up the power as necessary to try to achieve 3600 Pulses per second when commanded to run the motor at 100% speed, or at about 1800 Pulses per second when commanded to run the motor at a speed of 50%.

At full speed, 150 rpm, the NeveRest motor encoder will only produce 2800 Pulses per second. Using the 1440 PPR Tetrix motor with shaft encoder will produce 2800 ticks at 78% speed or 117 rpm. Since the motor controller will try to adjust power as necessary using the built in PID to achieve the correct speed, a speed setting of 78%, i.e. motor[motorD]=78; will achieve full speed on the NeveRest Motor. Likewise, a speed setting of 39, motor[motorD]=39; (½ of 78) will achieve approximately 50% speed on the NeveRest motor running under PIDControl. Any speed from 78% to 100% will cause the controller to run the motor at 100% speed. Please keep in mind that this only works this way under PIDControl and not under openLoop. Under openLoop mode you are just passing a percentage power to the motor controller and you will need to revert to using 0 through 100 for your power levels if you want to get full range & power out of the NeveRest motor.

[ftcTeam6389]

Thank you very much for this info @CougarRobot! Very helpful!

- - - -
Rachel
Team Captain
FTC Team #6389 - "The LazyBotts"

[Jay Clayton]

Team #7060 Fried Fuzes , would like to know if anyone using the NeveRest encoder cable, black end will not fit in the Motor Controller. With some trimming of the black plastic it will fit. BUT what is the proper direction in the MC ? Can anyone tell us what are the pin colors of the encoder port ? Yellow pin on the inside or outside , black end goes in MC both ways .

Thanx , Confused and Frustrated #7060

[PhilBot]

Hi

The Yellow wire is nearest to the outside of the Motor Controller.

Phil.

[Jay Clayton]

Originally Posted by PhilBot

Hi

The Yellow wire is nearest to the outside of the Motor Controller.

Phil.

Thanks for everyones help ��

[Sasha]

Image from AndyMark page

[dcribbs]

A couple of questions concerning using the AndyMark encoders on the NeveRest Motors with the new MRI controllers.

1.Which set of encoder wires work best (or with the least modification)?
a) am-2965 both ends white connectors
b) am-2992 one black, one white connector


2.What is the correct orientation for the encoder cables to plug into the new MRI controllers?

I read the above posts about the built in Hi-Technic controller. Has anyone had issues with the new MRI controllers? Any advice on using the encoders with autonomous?

Thanks for your help!