Magnetic Guns

Description: IC1 is a 555 timer operating in astable mode, generating approximately 10 ms pulses for decade counter IC2. IC2 is continuously reset through resistor R3 until pin 15 is pulled low via the "Fire" button. Upon activation, IC2 sequences through outputs Q1 to Q7, powering transistors TR1 to TR4, which sequentially energize electromagnets L1 to L4. The secondary of transformer T1 provides 18 volts at 1 amp AC. Once rectified and smoothed, this voltage supplies 25.2 V DC to electromagnets L1 to L4. Resistor R4 reduces the voltage by 12 V to ensure that supply voltages for IC1 and IC2 are within acceptable limits. The electromagnets are constructed on a 25 cm long, 3 mm diameter copper tube, which can be sourced from hobby shops. Tin "stops" can be cut for each electromagnet, with approximately 500 turns of 30 SWG enamelled copper wire wound between them. The electromagnets should be mounted on a base of reversed sellotape for easy adjustment along the copper tube. A 3 cm long piece of 2 mm diameter galvanized wire serves as the slug, designed to slide loosely inside the copper tube. The effectiveness of the gun is significantly influenced by the adjustment of variable resistor VR1 and the positioning of electromagnets L1 to L4 on the copper tube; the provided values and measurements are merely guidelines. Initially, with L2 to L4 disconnected, VR1 should be adjusted and L1 positioned for optimal performance, using a wire inside the tube to gauge the slug's jump distance with L1. Following this, L2 should be connected and positioned for maximum effectiveness, allowing the slug to exit the tube. This process should be repeated for L3 and L4, as each electromagnet contributes to enhancing the gun's range. Future publications will detail methods for landing small projectiles on Mars.

The circuit utilizes a 555 timer (IC1) in astable mode to create a pulse-width modulation signal, which is critical for driving the subsequent decade counter (IC2). The frequency of the pulses generated by IC1 can be adjusted by modifying the resistors and capacitors connected to it, allowing for flexibility in the timing parameters of the system. The decade counter IC2 counts the pulses and provides outputs that enable the sequential activation of the power transistors (TR1 to TR4). These transistors act as switches that control the current flowing to the electromagnets.

The transformer (T1) steps down the mains voltage to a manageable level, and the rectification process converts the AC voltage to DC, which is then smoothed using capacitors to ensure a steady supply for the electromagnets. The design incorporates a resistor (R4) to further regulate the voltage supplied to the timing circuits, ensuring that the integrated circuits operate within their specified voltage ranges.

The construction of the electromagnets involves winding enamelled copper wire around a non-magnetic core, which enhances the magnetic field generated when current flows through the coil. The adjustable positioning of the electromagnets on the copper tube is a critical factor in optimizing the performance of the device, as it allows fine-tuning of the electromagnetic field strength and the effective distance the slug can travel.

The slug's design, using galvanized wire, ensures that it is lightweight yet sturdy enough to withstand the forces generated by the electromagnets. The overall assembly allows for rapid sequential firing of the electromagnets, creating a propulsion effect that launches the slug from the tube. This project demonstrates a practical application of basic electronic components and principles in creating an effective electromagnetic propulsion system.IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to TR4, which fire electromagnets L1 to L4 in rapid sequence. Transformer T1 secondary is 18 volts 1 amp A. C. When rectified and smoothed, this provides 25. 2 V D. C for electromagnets L1 to L4. Resistor R4 drops 12 V to obtain a supply voltage low enough for IC1 and IC2. The electromagnets are wound on a 25 cm long, 3 mm dia. copper tube (available at hobby shops). Two "stops" may be cut from tin for each electromagnet, and 500 turns of approx. 30 swg. enamelled copper wire wound between them. The electromagnets should be wound on a base of reversed sellotape, so that one may slide them on the copper tube. The slug (or "bullet") is a 3 cm long piece of 2 mm dia. galvanized wire, which should slide loosely inside the copper tube. Most crucial to the effectiveness of the gun are the setting of VR1 and the positions of electromagnets L1 to L4 on the copper tube (the values and measurements shown are merely a guide).

Firstly, with L2 to L4 disconnected, VR1 should be tuned and L1 positioned for optimum effectiveness (place a wire inside the tube to feel how far the slug jumps with L1). Then L2 (now connected) should be positioned for optimum effectiveness (the slug will now exit the tube).

Repeat with L3 and L4. Electromagnets L2 to L4 were each found to substantially increase the range of the gun. In a forthcoming edition of EPE, the author will describe how readers may land a small projectile on Mars.