As his latest project, YouTuber Tom Stanton wanted to explore what it would take to create a DIY electromagnetic rail launcher system. While electric motors work by passing a current through a coil of wire within a ring of magnets to create rotational movement, a linear system propels a magnet forward by applying a current to a copper coil and then quickly removing that current when the magnet is at the halfway point to avoid a collision. With the theory figured out, Stanton moved onto building a very small prototype.
For a basic proof of concept, Stanton designed a simple system that utilizes a hall effect sensor to detect when the magnet both passes in front of it and leaves its detection range. Once the magnet is detected, current is applied, and once the magnet leaves, the coil's circuit is disconnected. A pair of spools were 3D-printed and screwed into an aluminum extrusion, with about 80 wire turns per coil.
And from here, Stanton ran a quick test and was able to launch a tiny sled that had magnets on either side, although the acceleration was not too impressive, so he had to significantly increase the number of coils along the sled's path.
Giving enough current at a fast speed was accomplished by wiring up a bank of supercapacitors that can supply up to 100A of current per coil. In order to deliver all of this power, there is a pair of copper strips along the underside of the aluminum extrusion, with one being the positive terminal and the other as the ground terminal. The positive side is permanently connected to the coils, whereas the ground side of the coils is connected to the drain pin of a MOSFET that closes the circuit with the source pin when the gate is toggled high. As one might envision, this MOSFET can get quite hot, so a custom heatsink was milled from aluminum and attached to both the MOSFET's surface and the extrusion.
The job of quickly switching the coils falls on a microcontroller which continually reads the state of the hall effect sensors and toggles the copper coils accordingly. One advantage of using an MCU is the ability to add extra safety mechanisms, including the ability to limit how long a coil can be active and an arming system to ensure the system can't be powered on by accident.
With all 20 coil pairs and hall effect sensors soldered in place, Stanton moved onto the process of testing his new creation. After playing around with launching a paper airplane, along with a few other things, from a table indoors, they took it outside to calculate the full capabilities of the system.
Stanton observed the sled was able to accelerate up to 11m/s in just under 1/10th of a second for a total of about eight Gs of acceleration. For a future project, he hopes to experiment with different magnet configurations and find out which one works the best.