Arduino and Electronic Building Blocks

Most Arduino and electronic projects are made up of one or more building blocks attached to each other. Below are a variety of building blocks I find useful:

Connecting a 5V motor to an Arduino with a transistor
Creating a single pulse when activated
Electret Microphone Pre-amplifier
Connecting a higher voltage motor to an Arduino with a transistor

Connecting a 5V motor to an Arduino with a transistor

Arduino can deliver at most 40mA, too little for almost all but the tiniest motors. By using a transistor, the 40mA of Arduino is amplified to control the much higher current of the motor.

Connecting a 5V motor to an Arduino using a transistor

Connecting a higher voltage motor to an Arduino with a transistor

Arduino is strictly a 5V device, but a transistor can be used to control a motor powered by a voltage higher than Arduino.

arduinoMotor_schemarduinoMotor_bb

Creating a single pulse when activated

oneShot

This circuit uses the popular 555 timer in a monostable configuration. The output (LED in this example) is normally off, until the switch is closed momentarily. The LED stays on for about 1 second, regardless of whether the switch is let go or not. After being on for a second, the LED will not light again until the switch is opened and closed again.

R3 and C2 determine the length of time the LED is on. The on time T(on) is:

T(on) = 1.1 * R3 * C2

Instead of the LED (and its resistor) a relay or transistor could be used to activate some other device

Electret Microphone Pre-amplifier

If you want to use an electret microphone with Arduino or with a power amplifier, you first need to magnify the signal 10-100 times. This circuit does that.  R5, the 100K potentiometer, controls the gain: The larger the value, the more gain. I’ve had good results with a fixed 10K resistor.

lm741MicPreamp_schem

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