Robotics Education & Competition Foundation
Online Challenges

Amperage / Voltage Meter


Entry ID #: 3191
Created: Mon, Jan 9, 2017 9:23 PM


What is it?

This year for the Make It Real CAD Engineering Challenge our team, Freezing Code, designed an amperage and voltage meter. The purpose of this part is to be able to monitor the voltage of the battery, and more importantly the current draw of a connected motor. This would help teams diagnose problems with drawing more amperage than the motor, cortex, or power expander can handle. This would help teams balance amperage consumption across the available circuit breakers in order to maximize their robots operable time.

Final Report

A common problem that often arises in our team, as well as in other teams, are motors drawing too much current. When this happens the motors can cause a circuit breaker to be tripped because at times they can draw more than four amps. This results in an entire bank of motors to perform suboptimally or not at all. A solution to this problem would be to balance the current load across the three available four amp circuit breakers, two in the Cortex and one in the power expander. This is difficult to do however because there is not an easy way to determine how much current each motor is drawing. So our part design is an amperage and voltage meter, this would allow teams to monitor how much current individual motors are drawing. This would be very useful when trying to determine the best way to balance amperage consumption. This would allow teams to ensure that their robot does not draw more than four amps on each breaker. This would also allow teams to monitor the voltage of their batteries to ensure the best possible performance.

Our part can be attached to an existing robot by using up to four standard VEX bolts and nuts. The hole pattern in our part uses half inch increments to ensure compatibility with the VEX EDR mounting system. The voltmeter is connected in parallel with the positive and negative leads, and the ammeter is connected in series with the positive lead. The data wire is left as a pass through so that the meter can be connected before the motor controller. The meter would then be connected in line with the Cortex or power expander and a motor controller or in line with a motor controller and a motor. Teams could then use the meter to monitor the voltage and amperage of the robot. By utilizing this part in a completed robot, teams can optimize their robots power consumption, and diagnose problems concerning voltage and amperage draw.

Our team used Autodesk Inventor Professional 2017 when modeling this part. It allowed us to create an enclosure for the electronic components that would be compatible with other VEX EDR components. Utilizing this software allowed us to ensure that the two piece enclosure would fit together while maintaining manufacturing tolerances. We could now use this model created in Inventor to 3D print our part in order to test the real world functionality. Our team will continue to use Inventor in the future because it allows us to model our robot before fabrication, this reduces the cost of building a robot because we know ahead of time what parts and fabrication we will need. Using this software will benefit many of our members in the future because most of our members are seeking careers in engineering, which uses a lot of CAD software in order to fabricate parts and mechanical systems.

After creating this part our team was able to diagnose problems we were having with circuit breakers tripping off, and were able to solve the problem. Without this ammeter and voltmeter, it would have taken our team a lot longer to diagnose and fix the problem, this is because we would have had to guess and check to see which motors were drawing the most current. This meter made it much easier to be able to distribute our robots amperage consumption across the three circuit breakers, which allowed our robot to be operable for a much greater amount of time. This shows that our part offers tangible benefits for all teams seeking to fix and optimize their robots electrical consumption.