--- title: "Data logger and remote control block diagrams" subject: "Basic Electronics Engineering" chapter: 7 key: "semester_2/basic_electronics_engineering:data-logger-remote-control" source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/data-logger-remote-control site: BCT Engineering --- # Data logger and remote control block diagrams Basic Electronics Engineering · Chapter 7: Application of Electronic System - Asked in: 2069 Bhadra, 5+5 marks - Video: [data acquisition system | data acquisition system in hindi | block diagram | integration in iot |das](https://www.youtube.com/watch?v=MJ2PwmHxpv0) — Mind of Engineer - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/data-logger-remote-control - Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-7 ## Question Draw and explain the block diagram of data logger and remote control. ## Short answer A data logger samples sensors, conditions signals, multiplexes, holds, digitizes via ADC, and stores timestamped data using microcontroller and memory. A remote control uses an IR transmitter with a keypad, encoder, 38 kHz modulator, and IR LED; receiver uses an IR photodiode, amplifier, band-pass filter, demodulator, and decoder to execute commands. ## Answer #### Data logger (5 marks) A **data logger** automatically measures and records physical quantities over time. ```text Sensors -> Signal -> MUX -> S/H -> ADC -> Micro-controller conditioner | | | +--> Memory Real-time clock ----------+ +--> Display / PC ``` 1. Sensors convert temperature, pressure, voltage, etc. into electrical signals. 2. The signal conditioner amplifies and filters them. 3. The multiplexer selects one channel at a time, and the sample-and-hold keeps the value steady. 4. The ADC converts it into digital data. 5. The microcontroller adds a time stamp from the real-time clock, stores the data in memory, and shows it on a display or sends it to a computer. #### Remote control (5 marks) A **remote control** operates a device (TV, AC, fan) wirelessly from a distance, usually with infrared (IR) light, using a coded pulse train. ```text Transmitter: Keypad -> Encoder IC -> Modulator -> IR LED (38 kHz) ......... infrared light ......... Receiver: Photodiode -> Amplifier -> Band-pass -> Demodulator -> Decoder -> Controller (IR sensor) filter / device ``` **Transmitter:** pressing a key makes the encoder generate a unique binary code. This code modulates a 38 kHz carrier, and the IR LED sends it as light pulses. **Receiver:** the IR photodiode detects the light, and the amplifier and band-pass filter select the 38 kHz signal. (An integrated IR receiver module such as the TSOP1738 contains the photodiode, amplifier, filter and demodulator in one package.) The demodulator recovers the code, the decoder interprets it, and the controller carries out the command (channel change, volume). Advantages: convenient, low cost, no wires. Limitations: needs line of sight and has a short range (about 10 m). RF remote controls work without line of sight. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In the data logger, where does the microcontroller get the time stamp? A. From the ADC B. From the real-time clock C. From the memory D. From the sensor Answer: B. The real-time clock supplies the time that is stored with each reading. (Key point: Time stamp in data logger) 2. What happens in an IR remote transmitter when a key is pressed? A. The photodiode amplifies the light B. The decoder runs the device C. The encoder generates a unique binary code which modulates a 38 kHz carrier for the IR LED D. The IR LED sends steady light with no code Answer: C. The key code from the encoder modulates a 38 kHz carrier and the IR LED sends it as light pulses. (Key point: Remote transmitter) 3. How does the receiver recover the command? A. The LED detects it directly B. The photodiode detects the IR, the amplifier and band-pass select 38 kHz, the demodulator recovers the code and the decoder interprets it C. Through radio waves only D. The modulator removes the code Answer: B. After detection and filtering at 38 kHz, the demodulator recovers the code and the decoder passes the command to the controller. (Key point: Remote receiver) 4. What is a limitation of an IR remote control? A. Needs wires B. Works through walls C. Cannot send codes D. Needs line of sight and has short range (about 10 m) Answer: D. IR light needs a clear line of sight; RF remotes avoid this. 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