Over the last few videos I have highlighted helpful circuits. In this video, I highlight an active filter setup utilizing an operational amplifier. Filters are very helpful when working with analog signals. Often the range of frequencies needed are not across the entire band, therefore you need to filter out those that inhibit a clean […]
Building upon my last video, I’ve decided to make a simple circuit using some op-amps. One is the general op-amp LM741. The other is a specific op-amp, LM386, that is designed for audio amplification. This circuit can be used to amplify microphones or be used as a circuit sniffer depending on what you connect to […]
Infrared Pulse Sensor is the latest addition to our beginner-friendly series of Weekend Projects. Inspired by a photoresistor pulse sensor, MAKE’s Technical Editor Sean Michael Ragan built this IR-based pulse sensor using emitter and detector diodes, combined with an LM384 op-amp IC and an Arduino.
Scott Harden’s DIY electrocardiogram (ECG) uses a LED shining light through his finger into a photo transistor, with the resulting signal amplified with a LM324 quad op amp. The goal of this project is to generate an extremely cheap, functional ECG machine made from common parts, most of which can be found around your house. […]
On Make: Projects, Jason Poel Smith uses a pair of LM741 op amps to build an self-dimming night light that turns itself off after a period of time so you don’t waste electricity. The timer is made from a 741 op amp (operational amplifier) wired as a comparator. It compares the voltage across a capacitor […]
Instructables user diy_bloke built this op-amp controlled pump for his garden, using the classic 741 operational amplifier. He wrote a very detailed how-to including showing how to etch a PCB, as well as how to make a humidity sensor out of gypsum: The simplest form of a soil humidity sensor is made from two galvanized […]
Build an optical guitar using a common LM386 audio amp chip.
