Elektor Electronics 302 Circuits Pdf 14 «2024»

Duration: 3 hours Total marks: 100

Instructions:

Section A — Short answer and identification (20 marks)

Section B — Circuit analysis and calculations (30 marks) 6. (8 marks) A linear regulated power supply in the book uses a transformer, bridge rectifier, smoothing capacitor, and a 5 V regulator. Given: transformer secondary 12 VAC RMS unloaded, bridge diodes each drop 0.7 V, smoothing capacitor large enough to ignore ripple for DC estimate. Calculate the approximate DC voltage at the regulator input after rectification (show steps). State whether a 7805 regulator will have adequate headroom.
7. (8 marks) An audio preamplifier uses an op-amp with gain set by Rf and Rin. If the desired voltage gain is 20 (26 dB) and Rin = 10 kΩ, compute Rf. Also compute input and output impedances in the non-inverting configuration and note how to increase input impedance.
8. (8 marks) A transistor amplifier stage in one circuit uses an NPN BJT biased with a collector resistor RC = 4.7 kΩ and Vcc = 12 V. The design aims for collector quiescent voltage at half supply. Calculate collector current and choose an emitter resistor RE (approx) to set emitter at 1/10 of Vcc for thermal stability; assume β = 100 and design collector current equals collector-emitter quiescent current.
9. (6 marks) A timing circuit uses a 555 in astable mode. Given RA = 1 kΩ, RB = 47 kΩ, C = 10 µF: compute approximate frequency and duty cycle. Show formulas used. Elektor Electronics 302 Circuits Pdf 14

Section C — Design and application (30 marks) 10. (10 marks) Design a compact, battery-powered LED flasher (approx 1 Hz) based on a circuit concept from “302 Circuits”. Requirements: runs from a single 3.7 V Li-ion cell, drives a white LED (forward voltage 3.0 V) at 20 mA with suitable current-limited pulsed drive, uses minimal parts, includes a schematic and component list with values, and explains how you ensure safe battery discharge and LED current limiting. (Include a short PCB/component placement note.)
11. (8 marks) Modify a published tone-generator circuit (astable op-amp or NE555) to produce an adjustable square-to-sine-like audio output from 400 Hz to 4 kHz with amplitude suitable for feeding into a small power amp (line-level). Provide a block diagram, component choices, and explain how tone and waveform shaping are achieved.
12. (6 marks) Propose an EMI mitigation plan for a switching power-supply circuit found in the collection: list five practical measures (e.g., snubbers, layout changes, filtering) and briefly explain the purpose of each.
13. (6 marks) Select one project-type from the book (e.g., FM transmitter, logic trainer, measurement accessory). Describe enhancements to improve reliability and usability: three hardware changes and two documentation/user-interface improvements.

Section D — Troubleshooting and modification (20 marks) 14. (8 marks) You assemble a DC motor speed controller from the collection but find the motor judders and supply voltage drops under modest load. Provide a step-by-step troubleshooting checklist (8 key tests or checks), explain what each test reveals, and recommend likely component-level fixes.
15. (6 marks) A published audio amplifier produces audible hum at 50/60 Hz. List five probable causes and for each give one corrective action.
16. (6 marks) You want to adapt a circuit that uses an obsolete IC specified at ±12 V to work from a single 12 V supply with minimal redesign. Outline a practical approach (6 concise steps) including level shifting, virtual rails, or selecting modern equivalents.

Grading rubric (brief)

Supplementary materials (optional, not graded)

End.

The term "Pdf 14" often refers to the indexing of these books in digital archives. While having a digital backup is incredibly convenient for searching and printing PCB layouts, it comes with a challenge: component obsolescence. Duration: 3 hours Total marks: 100 Instructions:

If you decide to build a project from 302 Circuits, you will likely encounter components that are no longer manufactured. Specific transistors (like the BC547 or power MOSFETs of that era) or logic chips (4000 series CMOS) may require modern equivalents. However, this presents a final educational challenge—the ability to read a datasheet and find a modern substitute that matches the voltage and current characteristics of the original part.

If you landed here by searching that exact phrase, you are likely looking for a specific digital version. Let's break down what each part of the keyword implies:

Most plausibly, "14" refers to a specific scanned file in a sequence. If you have "parts 1-13" already, part 14 would contain circuits #281 to #302, or possibly the index and schematic corrections. Section A — Short answer and identification (20 marks)

Let’s say you successfully extracted the PDF and want to build Circuit #147: "Ultrasonic Motion Detector" (a classic).