Tag Archives: LM324

DIY SWR and Power Meter


diycrap.blogspot.com has build a SWR and power meter based on Arduino Nano and LCD display:

First of all, this SWR meter in this article is not exactly homebrew, as I based the circuit on the schematic in the excellent book Arduino Projects of Amateur Radio. Although I bought the book and respect the copyright of the authors I will share my own schematic here. Why? First, the design in the book is not completely original and is based on similar designs from others. One example here. Second, I changed a few things, removed some stuff, and added some other things, to my own liking, so the design is not identical anymore.

DIY SWR and Power Meter – [Link]

Simple temperature control system


A simple temperature control system for 3D print or other constant temperature control purpose by Xiang:

I plan to build a home-made 3D printer controlled by my Raspberry Pi, which, unfortunately, does not have any analog data acquisition pin. Therefore I decide to build a stand-alone temperature control system.
The idea is very simple. I use a power resistor as the heater and a thermistor as the temperature sensor. The system contains an LM324 quad op-amps chip. One op-amp is used as a comparator to compare the thermistor resistance with a nominal resistance and output LOW or HIGH as the comparison result. The other three op-amps inside the LM324 are used to perform some linear transformation and output a voltage that is proportional to the thermistor temperature. This voltage is applied to a 0-30V voltmeter so one can read the temperature. A N-Channel MOSFET transistor is used to control on/off of the heater.


Simple temperature control system – [Link]

Simple DIY ECG + Pulse Oximeter


Scott W Harden writes:

I re-vamped my DIY ECG project. This new project is fully documented and uses extremely common and cheap parts, all of which could be purchased at RadioShack. It serves at both an ECG *and* a pulse oximeter, depending on which leads are attached. It uses a single chip (LM324, a quad operational amplifier) with a virtual ground to eliminate the need for a negative voltage. As a pulse oximeter with a 12V supply it outputs clean 10V swings when pulses occur. It’s intentionally unsophisticated, and made to be easy to replicate by anyone interested in electronics. Although you could view its output on an oscilloscope, it’s designed to be output into a PC sound card for recording (if attenuated to microphone levels). I even describe how to spectrally process the data on the computer to clean it up, downsample it, and graph it in Excel or with a Python script.

Simple DIY ECG + Pulse Oximeter – [Link]


The LM324 Quad Op-Amp Line Follower Robot with Pulse Width Modulation

ermicro.com writes:

Designing a simple and yet functional Line Follower Robot (LFR) is always a fascinating and challenging subject to be learned, the LFR actually could be implemented in many ways start from a simple two transistors to a sophisticated PID (Proportional, Integrate and Differential) which take advantage of the programmable feature of microcontroller to calculate the PID equation to successfully navigate the black track line on a white background surface.

The LM324 Quad Op-Amp Line Follower Robot with Pulse Width Modulation – [Link]


Op-amp Line Follower Robot with PWM Motor Control

This project is a line follower robot built around the LM324 quad op-amp. It uses two of the amp circuits in a triangle generator. The other two amps operate as hi/lo comparators. They compare the voltage across the photoresistors with the triangle wave, and thus determine if the robot is moving over the line or the whitespace. [via]

Op-amp Line Follower Robot with PWM Motor Control – [Link]

10 LED VU Meter Project by LM3915 and LM324


VU (Voltage Unit) meters are often included in analog audio equipments to display a signal level in Visual Units. We are building a mono input VU meter in this project. You can build one more to use them in stereo mode. Input sensitivity is about 1 Volt rms, up to +6dB. You can adjust the amplitude of the input by using the multiturn 50k linear potentiometer (POT1).

10 LED VU Meter Project by LM3915 and LM324 – [Link]