Science Buddies: "Ask an Expert"

Posted on behalf of student
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I have been trying to follow one of the tutorials on your website for making a model mass driver: https://www.sciencebuddies.org/science- ... r#abstract.

I have been having an issue with having the current actually run through the coil. I have done some troubleshooting, such as directly connecting the coil to the battery and it works so I know it is not a problem with the power source. I've also tested the Hall Effect sensor and it seems to be in working condition.

The issue is that the MOSFET driver module does not light up when the program is run and I cannot figure out what might be causing the interruption in connection. Is there perhaps a clearer photo of the wiring set up and an explanation as to how the wires should be put into the MOSFET? So far I've had to unscrew and rescrew to hold the wires in place.

Additionally, I am using an R4 Arduino Uno rather than the R3 that is used in the video. Does this board require any different wiring?

Hi - a few things:

1) The UNO R4 and R3 should be interchangeable as far as this project is concerned, the wiring is not any different.
2) Please refer to Figure 6 in the project procedure for building the circuit, it shows all the proper Arduino pin connections and using a wiring diagram like this is much better than trying to use a picture or pausing the video.
3) To debug a complex system like this, it helps to isolate components and test them one at a time. This can require changing your code. For example, you could initially "hard-code" your program to turn the MOSFET driver on and off (using digitalWrite and delays, similar to what you would do to blink an LED), ignoring the input from the Hall effect sensors. This will help you make sure that your driver board is working. Separately, you could just read the input from your Hall effect sensors and hold a permanent magnet near them to activate them, using a serial print command to print out when a magnet is detected - this time, ignoring the outputs to the driver board. This helps you make sure that your inputs and outputs are working independently before you try getting them to work together.

This is an advanced, complex project, so if you are new to Arduino we strongly recommend going through at least the first 7 or so videos in our Arduino tutorial series before you proceed and attempt the troubleshooting steps above: https://www.sciencebuddies.org/science- ... an-arduino

Hope that helps,

Ben