The following DC Power supply circuit is a linear power supply (using transformer). The voltage output of 13.8V power supply is highly regulated, can be adjusted in the moderate range, at up to 20A continuous current. This power supply is suitable for use for amateur radio equipment. DC Power supply is easily constructed and suitable for heavy duty because it is very efficient, small and lightweight.

In the DC power supply presented here, the pass transistors are located in the negative rail and connected in common-emitter configuration rather than as emitter-followers. Thanks to this, the regulator’s minimum voltage drop is extremely low, only about 0.1V for the transistors plus 0.5V for the equalizing resistors.

The other advantage is that the collectors are directly connected to the negative pole of the power supply’s output, which in most applications is grounded. That means that no insulation is required between the transistors and the grounded power supply cabinet! This eases the cooling very considerably. Thanks to the low regulator drop, a low cost 25V filter capacitor can be used.

Some Notes of DC Power Supply Circuit

• Use a transformer for the primary voltage you need. The 3A fuse is for 220 or 240V primaries. If you use something in the neighborhood of 110V, use a 6A fuse.
• The rather high transformer rating of 35A accounts for the losses that occur due to the capacitive input filter. If your transformer is rated for capacitive input, then a 25A value is enough.
• Of course you can make up C1 by placing several smaller capacitors in parallel. Likewise, the 0.1 Ohm, 5 Watt resistors can be made up by several in parallel, for example by 5 resistors of 0.5 Ohm, 1 Watt each.
• The LM336Z-5.0 voltage reference IC should not be replaced by a zener diode. Zeners are not nearly as stable. A different voltage reference IC can of course be used, if R2 and R3 are modified for the different voltage.
• D1 and Q2 through Q6 need heatsinking. Only Q2 needs insulation. D1 dissipates up to 60W, Q2 up to 25W, while the pass transistors dissipate up to 30W each in normal use, but may reach a level of 130W during short circuit! Take this into account when choosing the heat sink!
• R5 exists only to make sure that the transistors can actually be driven off. The 741 is not a single-supply operational amplifier, so it cannot drive its output very low. If a true single-supply opamp is used, then R5 becomes unnecessary.
  

The audio system in our cars is an assortment of different parts. Each and every part in the system performs a specific function. It is with the co-ordination of all the parts, that you can hear the system play those fantastic tracks as you drive along. In the entire system, car audio capacitors have a significance of their own.

What are car audio capacitors?

Car audio capacitors are basically power storages in the car. These capacitors accumulate that power which is essential for the amplifier to produce great sounds. You can hear the booming bass sounds and songs with that much needed punch only because of audio capacitors. Car audio capacitors are also known as stiffening capacitors.

More on car audio capacitors

• Audio capacitors accumulate power whenever it is not required. This power is released when the demand for power exceeds the supply capacity of the power system of the car.

• Audio capacitors are necessary to supplement the regular power supply of the car in order to ensure the smooth functioning of the amplifier. Car audio capacitors usually range from 0.5 farads to 3 farads.

• You have to install a car audio capacitor that complements your amplifier. It is also necessary to place the capacitor as near as possible to the amplifier. For 500 RMS of power output, it is necessary to have an audio capacitor of 0.5 farads.

• There are also digital audio power capacitors. These can also be installed in cars. A digital audio capacitor (usually from 1.5 farads) consists of a turn on and turn off circuitry along with a 24-volt DC.

If you car lights dim when your car audio system produces a deep bass note, then your amp will be greatly helped with a car audio capacitor.

How do I know I need A Capacitor?

Before installation, its often difficult to predict whether or not a capacitor will be beneficial to you. Its generally best to install the audio equipment prior to making the determination, so that you can address which symptoms need to be remedied and assess the severity of the symptoms. This will not only help you decide whether or not you need a capacitor, but also how much capacitance would be beneficial.

The most common symptom in need of added capacitance is headlight dimming (and sometimes dimming of the interior/dash lights). Its caused by a drop in system voltage associated with excessive current draw. While there may indeed be several loads drawing substantial amounts of current from the electrical system (eg. heat, AC, and so forth), its usually the transient draws that best manifest themselves in noticeable dimming. This is partly because our visual systems are most sensitive to detecting rapidly changing intensity levels rather than steady absolute differences.

Once youve assessed whether or not the dimming is noticeable (and sufficiently annoying), you must decide whether a capacitor is warranted or if youd be better served by upgrading the alternator.After initially having your alternator and battery checked out (some places will do this for free), the choice should be based on the severity of the dimming.

A commonly-used estimate for determining the appropriate size capacitor is 1F/kW (one farad per kilowatt). For example, a system running at300W would need a 0.3F (or 300,000uF) capacitor. However, there are several variables at play here, including the capabilities of the vehicles electrical system (which generally varies from idle to higher RPMs), the efficiency of the amplifiers, and the listening habits of the user (ie. the tone controls and the type of music).

These factors should all be considered when making the determination. Moreover, the voltage drop can be so severe that added capacitance is nothing more than a band-aid. That is, even several Farads of capacitance would not be able to sustain the voltage for as long as the drop persists. This Is when an alternator upgrade may be in order.

How to wire a capacitor?

You can refer to a recent post on wiring Here

Already I have given you dark activated and Light activated alarm diagram.But this schema is totally different schema because this schema contains dark activated and light activated both parts.This schema should be given 9V power.You can select Dark activated or light activated mood according to s1 switch.




Note

# This schema operates with 9V power

# Use 8ohm speaker

# Build this on a PCB