OCR Engineering Programmable Systems Level 1/Level 2 Past Papers

Understanding electronic component functions is the foundation of this qualification. Resistors limit current flow — their value in ohms determines how much they restrict current (Ohm's Law: V = IR). LEDs require a current-limiting resistor in series to prevent burnout — calculate the required resistance as R = (Vsupply - VLED) / ILED. Capacitors store charge and release it — in circuits they can smooth voltage ripple (filter capacitors) or create timing delays (RC circuits). Transistors act as electronic switches controlled by a small base current — a small current into the base allows a larger current to flow from collector to emitter. Circuit fault-finding requires systematic thinking. Use a multimeter in voltage mode to trace the signal path: if the input has correct voltage but the output does not, the fault lies between those two test points. Short circuits (unexpected low resistance paths) can damage components — always check for shorts before powering a new circuit. Open circuits (broken connections) interrupt current flow — check all solder joints and component connections. For microcontroller programming, understand the distinction between digital inputs/outputs (two states: HIGH = 5V/3.3V, LOW = 0V) and analogue inputs (continuous range, typically 0–1023 on a 10-bit ADC). A simple program structure for a sensor-controlled output: (1) read sensor value; (2) compare against threshold; (3) set output HIGH or LOW. Document your programs with comments explaining each section — assessment rewards clear, well-documented code as much as functional code.