# Pulse Receiver Schematic Circuit Diagram

#### Versatile Circuit for Pulsed Fixed-Frequency Transmitters

This compact circuit, introduced here, is specifically designed for receiving signals from pulsed fixed-frequency transmitters. Notably, chest straps produced by reputable brands like Polar, Huger, Kettler, Crane, Outbreaker, and others, emit brief signal bursts at a frequency of 5.3 kHz. These signals are not only detectable but can also be harnessed for various personal projects, as demonstrated by the author on their website [1].

#### Signal Reception and Processing with Precision

In this circuit setup, a ferrite rod wound with 1000 turns of 0.2 mm enameled copper wire, in conjunction with a tuning capacitor, serves as the reception apparatus for the signals. The specific capacitor value chosen (22 nF) is tailored for optimal functionality at a frequency of approximately 5.3 kHz. However, it’s important to note that this value can be adjusted to accommodate different frequencies as needed. Once received, the signals undergo amplification courtesy of the operational amplifier IC1. Subsequently, a NAND gate (IC2) refines these signals, transforming them into a clean waveform characterized by sharp edges.

#### Flexible Power Supply Options

For power supply, the circuit is versatile and can be operated using any DC voltage source falling within the 9 to 18 V range. This adaptability ensures convenience in choosing suitable power sources based on specific project requirements. Additionally, there is a dedicated board layout accessible [2], which can be conveniently ordered through ThePCBShop [3], streamlining the construction process.

Web links

[1] http://www.elektor. com/080093

[2] www.thepcbshop.com

#### Understanding the NAND Gate: A Universal Logic Element

The NAND gate, derived from the combination of an AND gate and a NOT gate in series, is a fundamental logic component. Together with the NOR gate, NAND gates are often referred to as universal gates due to their versatility. These gates can be employed to execute any basic logic operation. Symbolically represented by a vertical bar or upwards arrow (A NAND B = A|B or A↑B), the NAND gate’s function is also known as the Sheffer Stroke Function.

#### Construction and Operational Principles of NAND Gates

NAND gates are constructed using transistors and junction diodes. According to De Morgan’s laws, the logic of a two-input NAND gate can be expressed as A • B = A + B. In essence, a NAND gate is equivalent to inverters followed by an OR gate. The truth table of a two-input NAND gate illustrates that the output is 1 when either A or B (or both) are at logic ‘0’. In other words, if both inputs, represented as A’ and B’, are 1, the output becomes 1. This property allows the NAND gate to perform the OR function by inverting the inputs.

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