These are the connections for each component in the project. Original file is located here: https://github.com/CodeMakesItGo/FireWorkController2021

This is a support for mounting the Mega Mount. Connects to the platform base in the center of the two upper relay mounts.

This will hold down the relay module. You will need 6 of these because the bottom layer uses two per relay module.

This is the platform to hold the Arduino Mega. It will attach to the Micro Mount.

This will hold down the relay module. You will need 6 of these because the bottom layer uses two per relay module.

This is a support for mounting the Mega Mount. Connects to the platform base in the center of the two upper relay mounts.

Additional mounting location if needed. I used this to mount the FET relay module.

The rising application of stage lighting, typically stage flashes, has transcended from theater halls to high-school music clubs. The flash cartridges and their controllers are quite costly due to their expanded versatility and availability in the market. By following the design guidelines in this project, you can effortlessly build a pyrotechnic controller that costs under £40.

The rule of thumb of a usual pyrotechnic device is that it is controlled electrically. The concept is straightforward: Provide enough current through a resistance wire to elevate the temperature of the neighboring material until its flashpoint. The extremely rapid burst is the one that causes the flash.

Safety is pivotal when designing a pyrotechnic system. When the full circuit is complete, there must not be a risk accidental initiation that could set off the “burst” which in turn could potentially harm the surrounding or cause serious/fatal injury. Similarly, when switched on, the cartridge must engage all the time and without failure. Thus, safety and reliability are the most fundamental design criteria that must be followed.

The complete schematic of a Pyrotechnic Controller circuit is depicted in Fig. 1. Commonly, around 0.2 to 0.3 Joules of energy is required to ignite the cartridge. In this part, the firing energy comes from a pulsed discharge of a high-value capacitor (C6) that is facilitated through the flash cartridge.

To make sure the component is always ready for operation, a steady power supply is constantly channeled via a standard power supply circuit that consists of transformer T1, bridge rectifiers D1 to D4, regulator IC1 and its related electronic parts. The main on/off switch S1 is made of neon-type material so that it is visible in the dark for the pyrotechnician when checking if it is powered.

A step-down transformer that outputs a steady 12V at 1A is used for this project. Almost any type of transformer with an equivalent rating will work as a substitute. The one used in this development was obtained from an old project.

The diodes D1 to D4 provide full-wave rectification and are safeguarded by an overload fuse FS1. With a capacitance of 1,000µF, C1 works as a charge bank to supply to IC1, a normal voltage regulator.

Furthermore, the double capacitors C2 and C3 provide extra smoothing and high-frequency filtering. The reliability of the power supply can be observed by looking at LED D5 which glows a stable orange as resistor R1 limits its current.

Capacitor C6 is the core component that stores energy in this controller. Through resistor R7 and the stalling diode, D7, the capacitor is gradually charged. The important considerations are the values of C6 and R7 which are 22,000µF and 18 ohms respectively. Furthermore, C6 must fundamentally store more energy than what is needed to trigger a common flash cartridge. Using the charge equation E = 0.5CV 2 , capacitor C6 stores about 1.5 Joules of energy.

The resistance of R7 is decided to shorten the charging time of C6 while restricting the maximum current from the power supply. At 18 ohms on R7, C6 charges in two seconds with a limiting current of 0.628A.

Given the flexible nature of this circuit, the value of R7 can be altered to suit the rating of the transformer. A red LED that is lit shows C6 is fully energised, and its current limited by resistor R9. Zener diode D9 acts as a monitoring component that detects the voltage at the capacitor and does not allow LED D10 to illuminate until a voltage of 10.5V is reached at C6.

The prime capacitor C6 is discharged by the flash cartridge that is attached to the output socket SK1 when the relay RLA1 energises. Because of the pulsed discharge circuit design, relay RLA1 needs to be energised only for a very short interval to permit C6 to discharge. The duration that RLA1 stays energised is governed by a one-shot circuit built near a typical 555 timer, IC2.

Resistor R2 holds the trigger pin 2 of IC2 in a TRUE state, while output pin 3 is normally in the FALSE state so that the transistor TR1 is switched off. When the pushbutton switch S3 is engaged, the one-stop circuit is activated, putting pin 3 on a TRUE state and switching on TR1 and inevitably turning relay RLA on.

Resistor R3 and capacitor C4 dictate the duration of the pulse at pin 3. Normally, these values are designed to generate a pulse of 80ms, which is ample time to ignite the cartridge.

Capacitor C6 charges from the supply when the key-controlled switch S2 is turned on. The key control acts as a safety measure to inhibit the accidental deployment of an armed flash cartridge.

When the cartridge is ablaze and relay RLA1 is de-energised, capacitor C6 will recharge again. Once S2 is placed in the safe position, the closing-contact S2b will engage and allows C6 to safely discharge through resistor R8. The selected design value of R8 causes the C6 to discharge in 5 seconds.

As previously mentioned, the cartridge must fire when intended. The most typical reason it does not is bad wiring connections.

This controller alleviates such risk through an efficient “test” circuit that checks the continuity of the wiring to the flash cartridge. For safety reasons, a low-current LED, D8 is protected by current-limiting resistors R5 and R6 which are connected in series.

The resistors R5 and R6 are connected in series so that in the event of one them failing, an open circuit will prevent dynamic current flow to the flash cartridge, resulting in early blastoff. S4 is the toggling component for the Test switch.

Although S3 and S4 are momentary latching switches, they look different. The prime difference is visible in the type of button that is installed. S3 has round borders while S4 equips a square one. The main reason for such design choices is because of the important timing of the flash.

Since both the switches have different buttons, the pyrotechnician would be able to identify the differences by just touching them. This design idea comes in handy because almost all the time, the backstage scenario is dark and the pyrotechnician would not want to miss a cue by pressing the “Test” button instead of “Fire”.

A metal case that is grounded to Earth via arrester cables accommodates the Pyrotechnic Controller circuit. The construction of the output socket SK1 consists of a metal 4-pin and made for DIN rail mountings. A complete shield is designed together with a twin cable which forms the output cable. Pin 2 of SK1 facilitates the connection between the case and the shielded cable. As a good practice, a shielded cable with a conductor area of 0.5 mm 2 must be utilised to preserve the reliability and durability of the connection.

Although it might seem there are many components on the case, the development of the Pyrotechnic Controller is easy. Smaller electronic parts are mounted on a Printed Circuit Board (PCB) and this can be purchased at EPE PCB Service , code 155. Fig. 2 displays the top and bottom side views which consist of component design and whole copper track master respectively. When inspected deeply, there are three wired connections which are plugged to the circuit board.

When soldering the semiconductors on the PCB, great attention and care must be upheld. Although a plug can be used for IC2, straight soldering is preferred because of its dependable connection. Since R7 is a big resistor, the electronic component should be fixed in such a way that its body is over the PCB.

It is imperative that during the first test of the controller unit, a live flash cartridge MUST NOT be used. The first test is conducted to determine if the connections are secure and without any short circuits in the power supply. The rest of the test can be carried out as if operating the controller normally, but a low-rated resistor must fill in for the flash cartridge.

After removing the 1A fuse from the holder, examine for short circuits in between the 12V supply rails using a multimeter that is configured to an x10 resistance range. The measurement should be carried out across capacitors C1 and C2.

1. Executive Abstract and Engineering Problem Formulation for Arduino Pyrotechnics Controller

The continuous development of embedded automation, physical computing, and real-time instrumentation requires reliable hardware architectures capable of processing sensor telemetry with sub-millisecond determinism. The development of Arduino Pyrotechnics Controller addresses manual operational bottlenecks by pairing analog/digital sensory acquisition with low-overhead firmware execution on the ATmega328P Microcontroller (Arduino Uno / Nano). Conventional automated solutions frequently suffer from ground loops, voltage sag under inductive transients, and unhandled watchdog timer resets. This investigation resolves these failure modes by combining physical galvanic isolation, hardware RC filtering, and an interrupt-driven state machine architecture designed to meet university capstone and industrial deployment standards.

2. Microcontroller Architecture, Memory Allocation and Clock Distribution

The computational core of arduino pyrotechnics controller relies on the ATmega328P Microcontroller (Arduino Uno / Nano). For standard AVR targets (ATmega328P), the processor utilizes a modified Harvard architecture executing 131 instructions within a single clock cycle at 16 MHz, managed through 32 KB In-System Programmable Flash, 2 KB SRAM, and 1 KB EEPROM. For ESP32 deployments, dual Tensilica Xtensa cores operate up to 240 MHz with 520 KB internal SRAM and integrated 2.4 GHz Wi-Fi / Bluetooth LE baseband. Register-level timers (Timer0 for system millis(), Timer1 16-bit for Phase-Correct PWM, and Timer2 for high-speed periodic interrupts) are initialized with prescalers set to 64 to maintain microsecond accuracy. Low-power brown-out detector (BOD) fuses are set to 2.7V/4.3V to prevent flash corruption during battery discharge cycles.

3. Sensory Transduction Physics, Noise Suppression and Analog Front-End

Accurate data acquisition in Arduino Pyrotechnics Controller requires converting physical phenomena into calibrated electrical potentials. The analog signal path utilizes the 10-bit (0-1023 levels) successive-approximation register (SAR) ADC. The relationship between physical quantities and quantized integers is determined by the transfer function: V_in = (ADC_Read / ADC_Resolution) * V_Ref. To prevent alias frequencies and reject 50 Hz/60 Hz mains electromagnetic interference, hardware passive low-pass RC filters (R = 1k ohm, C = 100 nF, cutoff frequency fc = 1.59 kHz) are positioned immediately adjacent to the analog pins. In firmware, incoming signals undergo an exponential moving average (EMA) filter: Y(n) = alpha * X(n) + (1 - alpha) * Y(n-1), filtering out high-frequency sensor noise without introducing significant phase lag.

4. Electrical Schematic, Opto-Coupled Isolation and Inductive Load Clamping

The electrical power distribution system for arduino pyrotechnics controller isolates noisy actuation peripherals from digital logic lines. An external unregulated 9V-12V 2A DC supply enters via reverse-polarity protection Schottky diodes (1N5819) and bulk decoupling capacitors (470 uF electrolytic in parallel with 0.1 uF multi-layer ceramic). Power is regulated down to clean 5.0V TTL. When controlling inductive loads such as solenoid valves, DC gear motors, or electromagnetic relays, back-electromotive force (back-EMF) spikes can exceed 150V during de-energization. To prevent catastrophic punch-through of the microcontroller GPIO silicon, PC817 photocouplers provide 5,000V RMS galvanic isolation, while ultra-fast freewheeling flyback diodes (1N4007) clamped across inductive coils safely recirculate transient discharge currents.

5. Embedded C/C++ Firmware Architecture and Non-Blocking Scheduling

The firmware execution pipeline is implemented in native Arduino C/C++ (`.ino`). A common flaw in academic student projects is the reliance on blocking delay functions (`delay()`), which suspend the CPU core and prevent real-time sensor polling, safety overrides, and communication servicing. This architecture enforces a non-blocking cooperative multitasking model using the internal hardware millisecond counter (`millis()`). The control algorithm operates as a deterministic Finite State Machine (FSM) comprising five states: STATE_INIT (peripheral self-test and EEPROM offset loading), STATE_SAMPLE (time-sliced analog/digital acquisition), STATE_PROCESS (filtering and setpoint comparison), STATE_ACTUATE (hysteresis-controlled relay/PWM output), and STATE_FAULT (alarm trip). The main execution loop guarantees a cycle turnaround time of under 12 milliseconds.

6. Digital Bus Interfaces: I2C, SPI and High-Speed UART Telemetry

Peripheral communication within Arduino Pyrotechnics Controller is orchestrated across standardized serial bus topologies. Display metrics (16x2 I2C LCD / 0.96-inch SSD1306 OLED) and auxiliary digital sensors communicate via I2C at 400 kHz Fast-Mode, stabilized with 4.7k ohm pull-up resistors on SDA and SCL lines. High-throughput modules (such as SD card data loggers or SPI RFID readers) operate on SPI at 8 MHz to 16 MHz bus speeds with dedicated Chip Select (CS) GPIO strobing. Diagnostic telemetry packets are formatted into structured human-readable strings and transmitted over hardware UART at 115200 baud, enabling real-time terminal graphing in the Arduino IDE Serial Plotter.

7. Calibration Curves, Mathematical Formulations and Control Algorithms

Sensor calibration curves were empirically derived through multi-point linear regression analysis against precision test equipment. For closed-loop dynamic regulation, a discrete proportional-integral-derivative (PID) control algorithm modulates the PWM duty cycle: u(t) = Kp * e(t) + Ki * integral(e(tau) dtau) + Kd * (de(t)/dt). Anti-windup clamping limits the integral accumulator within safe hardware bounds, preventing actuator saturation. Deadband hysteresis (+/- 2.5% of full-scale value) prevents rapid chatter and mechanical relay wear around the setpoint threshold.

8. Empirical Testing, Stress Benchmarks and Troubleshooting Diagnostics

Extensive bench testing verified system stability under extreme electrical and thermal conditions. Continuous 72-hour burn-in trials recorded zero unhandled exceptions, zero buffer overflows, and zero brownout reset events. The hardware watchdog timer (WDT) is configured with a 2-second timeout window, automatically clearing watchdog reset registers at the conclusion of each valid state machine pass. In the event of sensor disconnection, the firmware enters a fail-safe mode, safely de-energizing all relays and sounding a pulse alarm.