This article is from “Invention and Innovation” High School Edition, June 2023
Earlier this year, with the lifting of the firework ban, the community and streets are once again filled with “human fireworks.” Drones carrying fireworks are becoming increasingly popular. But how can we safely and effectively launch fireworks? Currently, the mainstream method is to ignite the fireworks on the ground and then let the drone take off urgently, but this method can easily lead to people being accidentally injured by fireworks or drones.
Is it possible to ignite them in the air? Looking at the self-made racing drone hanging on the wall, I had an idea—design an integrated reconnaissance drone.
According to its literal meaning, the integrated reconnaissance drone must have both the “reconnaissance” and “strike” functions, meaning it should have image acquisition and transmission capabilities, as well as a controllable ignition device that can carry explosives. The image acquisition and transmission system is already integrated into the aircraft, so the main consideration is the type of explosives and the controllable ignition device.
The fireworks available on the market that can be used as explosives include sparklers, sky rockets, firecrackers, and explosive-type fireworks. Sparklers have little power, while firecrackers and similar items may damage the drone. Considering all factors, I chose sky rockets as the onboard explosives.
The most important part of the ignition device is the heat source. According to the heating formula for conductors, the heating conductor must be chosen to have a much higher resistance than the wire to avoid overheating. According to Ohm’s law, the total resistance of the circuit cannot be too large to ensure that the main factor of heating—current—is sufficiently large. After analysis and calculation, I chose nickel-chromium alloy wire as the heating wire.
After selecting the material, the specifications of the alloy wire must be determined. I plan to use sanitary paper as the medium to ignite the fireworks fuse to improve the success rate. After researching, I found that to ignite sanitary paper, the heating power should not be less than 60 W. The cruising current of the racing drone is about 7 A, with an average standby voltage of about 16 V, and a cruising safety limit voltage of 12 V. The battery discharge rate is 100 C, with a capacity of 1550 mAh. After extensive theoretical analysis, I decided to use 2 cm long, 0.1 mm diameter alloy wire.
The flight control system of the previously self-made racing drone uses the Betaflight system, which is an open-source system. According to its open-source introduction, it supports servos. More importantly, this system supports outputting a PWM square wave signal with a 20 ms period. This means that the square wave signal can be used to drive a MOS integrated circuit, which in turn can drive a relay—serving as the driving part of the controllable ignition device.
Figure 1: Ignition Device Driver Circuit Board
Figure 2: Wiring Circuit Diagram
Figure 3: Physical Image
The ignition device is installed on the racing drone, and related channels are set, modifying the drone’s program. Since the heating element cannot be connected using traditional soldering methods, the wires must be fixed to the alloy wire using screws. The wires are made of high-temperature-resistant silicone to prevent damage from the tail flame.
Figure 4: Installation Effect Diagram
The testing effect of the integrated reconnaissance drone meets expectations, with good controllability and safety. Loading different fireworks can create many variations. For example, using the racing drone loaded with “Youth Interaction” fireworks for acrobatic flying can produce unique visual effects, adding joy to the festive atmosphere.
In addition, the airborne ignition setup enhances the safety of firework launches, avoiding the risk of ground ignition injuring people or causing fires.
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Source: “Invention and Innovation” High School Edition, June 2023
Editor: Qin Yinyin, Xia Yanhui
Reviewed by: Qin Yinyin
Final Review: Li Baichun