A better way to power car audio in home

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Usually, car audio systems like CD player or cassette player have good audio amplifiers, with four channels (front L/R and rear L/R) of enough power for in home use. The radio tuner is also of high quality, with automatic best frequency selection and RDS information. Not all car audio systems have audio auxiliary inputs, although with a little tweaking, you can add audio line level inputs to a cassette player so you can use it as audio amplifier with any audio source.

There are plenty of how-to's about this subject online. Yet I couldn't find one that handles the memory loss problem. Car audios are designed to be continuously powered by the battery. Therefore, most don't have a permanent storage memory for settings. Upon disconnecting the power, the device loses all audio settings and stored radio stations.

This article will deal with the memory loss problem. Unless you will never unplug the DC adapter from the mains, you will need something similar to what follows if you want to use a car audio device in home. Let's start with the basics.

The proper way to power car audio in home - with backup battery

DC Motor Controller for PCB Drill

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This is a simple circuit that can be use to vary the speed of a DC motor. It is very useful for controlling a PCB drill, but it can be used for whatever applications you want. The speed can vary from full to complete stop. The circuit is versatile and can be used with motors of different currents and voltages.

This circuit is widespread on the internet. Here is an example. The PWM signal is generated by a 555 chip. The chip drives a MOS-FET transistor that will switch the motor on and off. The 555 is powered from a 7805 regulator. Therefore, the motor DC voltage can be between 8 and 35 V (the circuit can be powered by AC 7...26 V). The maximum current is limited by MOS-FET.
The circuit shown here is designed to be AC powered by a mains transformer. But you can power it from a DC adapter, battery or even a computer power supply if you remove the diode bridge and connect the power lines straight to ground and positive pads, where the output pins of the bridge would otherwise fit.
DC Motor Controller for PCB Drill 555