Power Supply Circuit 12-15 Volt 20A

Output voltage of the power supply circuit is adjustable from fine potensiometer from 12V to 15v. It is suitable for all 12V power supply devices, or devices which are normally connected to a 12V battery or a vehicle with a 12V power supply system. This tension is usually 13.8 V.



For above reason, The Power Supply is also set to this tension, all right, however, any voltage from 12V to 14V. In this case, the tension is set somewhere around 13.6 V. To provide tension resistance in addition to voltage regulator 78S12. Instead potentiometer 100R inserted resistor 56R.



The scheme of the power supply is simple, but it is partly taken from some of the schemes taken up in the past. The material used is easily obtainable in electronic component shops, and this was the condition when I started to design this power supply.

ICL7107 Digital LED Voltmeter

This circuit is a digital voltmeter with LED display. It's ideal to use for measuring the output voltage of your DC power supply. It includes a 3.5-digit LED display with a negative voltage indicator. It measures DC voltages from 0 to 199.9V with a resolution of 0.1V. The voltmeter is based on single ICL7107 chip and may be fitted on a small 3cm x 7cm printed circuit board. The circuit should be supplied with a 5V voltage supply and consumes only around 25mA.



The use of 7805 5V voltage regulator is highly recommended to prevent the damage of ICL7107, 555 ICs and to extend the operating voltages.


Parts list of The Digital LED Voltmeter:

• R1 = 8K2 R1 = 8K2
• R2 = 47K / 470K R2 = 47k / 470K
• R3 = 100K R3 = 100K
• R4 = 2K R4 = 2K
• R5, R6 = 47K R5, R6 = 47k
• R7 = 0R / 4K7 R7 = 0R / 4K7
• R8 = 560R R8 = 560R
• C1,C5, C6, C8, C9 = 100n C1, C5, C6, C8, C9 = 100n
• C2 = 470n / 47n C2 = 470n / 47n
• C3 = 220n C3 = 220n
• C4 = 100p C4 = 100p
• C7 = 10-22u C7 = 10-22U
• D1, D2 = 1N4148 D1, D2 = 1N4148
• IC1 = ICL7107 IC1 = ICL7107
• IC2 = NE555 IC2 = NE555
• OPTO = CA 10 pin FTA = CA 10 pin

The digital LED voltmeter can also be configured to measure different voltage ranges and display higher voltage resolution.

Battery Low Voltage Beeper

This electronic circuit is an alarm circuit for low battery condition. It provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn of the impending loss of power. The circuit was designed for monitoring solar systems, but it could also be useful for automotive and other 12V applications.



How it works

U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED.




The beeper consists of U4, a tone generator, and U3, a low duty cycle pulse generator. The tone can be changed by adjusting R7, the beep rate can be changed by adjusting R5. A small amount of hysteresis is provided by R1 and the current through LED1 and the beeper, this separates the on and off points for the circuit.

U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED.

The beeper consists of U4, a tone generator, and U3, a low duty cycle pulse generator. The tone can be changed by adjusting R7, the beep rate can be changed by adjusting R5. A small amount of hysteresis is provided by R1 and the current through LED1 and the beeper, this separates the on and off points for the circuit.

Use of Battery Low Voltage Beeper

Connect the circuit to the 12V source that you wish to monitor. Turn S1 on, if the battery voltage is above the set point, nothing should happen.

As the battery voltage drops below the set point, the LED will light and a periodic beeping will come from the speaker. If the beeping becomes annoying, turn off S1. Be sure to charge the battery soon, excessive discharging will shorten the life of most rechargeable batteries.