Fall Biped 2016- Updated Stall Current Motor Experiment

By: Alan Valles (Electronics and Control)
Approved by: Ijya Karki (Project Manager)

Introduction

The Purpose of this experiment is to measure the stall current of the Pololu 1117 motor. This will be done in order to compare it to its rated value of 800mA.

Introduction

A stall current experiment was performed in order to see the actual stall current produced by Pololu 1117, this was done at the recommendation of Project Manager and ENC Division manager. Stall Current was measured utilizing two Pololu 1117 130 motors. The motors were set up in a mini vise as shown. Two small electrical loads were applied, one 100Ohm and One 1Ohm. The currents into the driving motor and out of the receiving motor were measured. As discussed in ENC meeting this should give us our stall current. The stall Current for the Pololu 1117 is rated at 800mA on the Pololu website.

The first run of test result in really low output currents to the motor load. However, this was due to the shafts losing grip of each other because the electrical tape overheated and began to lose grip of the two shafts. Thus, the receiving motor did not spin at a strong frequency with the other motor. The tape was redone and the experiment current increased by about 60%. Thus, the measured stall current would be around 492 mA. However, the measured current from inside a Tamiya gearbox was about 500mA so this value does not make sense. However, if another device could be used to tightly grip both motor shafts in order to better sync their frequencies than the number may have been closer to the rated 800mA. However, the rated 800mA was for 6v DC but the motor will be operating at 5V DC. As shown in the experiment. Taking the maximum motor value of 335 and multiplying by two we get, 670mA. This value is less than the rated 800mA rated stall current. One can figure that the actual stall current will be under the rated 800mA

Electrical Load	Driving Motor Current	Load Motor Current
100Ohm	321	50
1Ohm	335	100
1Ohm Redo	328	164

 Conclusion

In conclusion an experiment was done to measure the stall current of the Pololu 1117. The results were not definitive. However, using worst case analysis, the stall current of the Pololu 1117 motor can be seen as less than the 6v rating of 800mA since we will be operating at 5v.

Reference

[1] http://arxterra.com/pathfinder-motor-stall-current-test/