Showing posts with label low. Show all posts
Showing posts with label low. Show all posts
Saturday, September 28, 2013
Low Drop 5V Regulator
A 4-cell pack is a convenient, popular battery size. Alkaline manganese batteries are sold in retail stores in packs of four, which usually provide sufficient energy to keep battery replacement frequency at a reasonable level. Generating 5 V from four batteries is, however, a bit tricky. A fresh set of four batteries has a terminal voltage of 6.4 V, but at the end of their life, this voltage is down to 3.2 V. Therefore, the voltage needs to be stepped up or down, depending on the state of the batteries. A flyback topology with a costly, custom designed transformer could be used, but the circuit in the diagram gets around the problem by using a flying capacitor together with a second inductor.
The circuit also isolates the input from the output, allowing the output to go to 0 V during shutdown. The circuit can be divided conceptually into boost and buck sections. Inductor L1 and switch IC1 comprise the boost or step-up section, and inductor L2, diode D1 and capacitor C3 form the buck or step-down section. Capacitor C2 is charged to the input voltage, Vin, and acts as a level shift between the two sections. The switch toggles between ground and Vin+Vout , while the junction of L2, C2 and D1 toggles between –Vin and Vout +Vd1. Efficiency is directly related to the quality of the capacitors and inductors used.
Better quality capacitors are more expensive. Better quality inductors need not cost more, but normally take up more space. The Sanyo capacitors used in the prototype (C1–C3) specify a maximum ESR (effective series resistance) of 0.045 ½ and a maximum ripple current rating of 2.1 A. The inductors used specify a maximum DCR (direct current resistance) of 0.058 ½. Worst-case r.m.s. current through capacitor C2 occurs at minimum input voltage, that is, 400 mA at full load with an input voltage of 3 V.
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The circuit also isolates the input from the output, allowing the output to go to 0 V during shutdown. The circuit can be divided conceptually into boost and buck sections. Inductor L1 and switch IC1 comprise the boost or step-up section, and inductor L2, diode D1 and capacitor C3 form the buck or step-down section. Capacitor C2 is charged to the input voltage, Vin, and acts as a level shift between the two sections. The switch toggles between ground and Vin+Vout , while the junction of L2, C2 and D1 toggles between –Vin and Vout +Vd1. Efficiency is directly related to the quality of the capacitors and inductors used.
Better quality capacitors are more expensive. Better quality inductors need not cost more, but normally take up more space. The Sanyo capacitors used in the prototype (C1–C3) specify a maximum ESR (effective series resistance) of 0.045 ½ and a maximum ripple current rating of 2.1 A. The inductors used specify a maximum DCR (direct current resistance) of 0.058 ½. Worst-case r.m.s. current through capacitor C2 occurs at minimum input voltage, that is, 400 mA at full load with an input voltage of 3 V.
Saturday, July 13, 2013
Simple Battery Low Voltage Beeper Circuit
Simple Battery Low Voltage Beeper circuit 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.
Specifications:
Specifications:
- Nominal operating voltage: 12V
- Idle current: 6ma
- Low Voltage Warning current: 15ma
Theory:
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.
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.
Battery Low Voltage Beeper Circuit
Simple Battery Low Voltage Beeper circuit board was made by printing the pattern (see below) onto Press-n-peel blue circuit board transfer film with a laser printer. Etch the board, drill the holes, and assemble the parts on the board as per the board photo. Be sure to correctly orient the diode, electrolytic capacitors, ICs, and transistor. The CA3160 op-amp may be difficult to find, other low power CMOS op-amps may be substituted. A standard 741 op-amp would also work, but the idle current will be higher.
Alignment:
Connect the circuit to an adjustable DC voltage source. Set the voltage source to 11V or wherever you would like the circuit to turn on. Turn on switch S1. Adjust VR1 until the point where LED1 just comes on and the beeping starts.
Use:
Connect the circuit to the 12V source that you wish to monitor. There should be a fuse somewhere between the battery and this circuit. 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.
Alignment:
Connect the circuit to an adjustable DC voltage source. Set the voltage source to 11V or wherever you would like the circuit to turn on. Turn on switch S1. Adjust VR1 until the point where LED1 just comes on and the beeping starts.
Use:
Connect the circuit to the 12V source that you wish to monitor. There should be a fuse somewhere between the battery and this circuit. 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.
Tuesday, May 14, 2013
Low Voltage Cable Cross SectionMonday, May 13, 2013
Brightness controller for low power lamps
This is a circuit which can control the brightness.This circuit base on NE555 IC.This circuit can be used to control the speed of DC motors.
Notes.
* The switch S1 can be SPST ON/OFF switch.
* The lamp L1 can be a 6V / 200 mA lamp.
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Notes.
* The switch S1 can be SPST ON/OFF switch.
* The lamp L1 can be a 6V / 200 mA lamp.
Sunday, March 31, 2013
500W Low Cost 12V to 220V Inverter
Attention: This Circuit is using high voltage that is lethal. Please take appropriate precautions
Using this circuit you can convert the 12V dc in to the 220V Ac. In this circuit 4047 is use to generate the square wave of 50hz and amplify the current and then amplify the voltage by using the step transformer.
How to calculate transformer rating
The basic formula is P=VI and between input output of the transformer we have Power input = Power output
For example if we want a 220W output at 220V then we need 1A at the output. Then at the input we must have at least 18.3V at 12V because: 12V*18.3 = 220v*1
So you have to wind the step up transformer 12v to 220v but input winding must be capable to bear 20A.
readmore...
Using this circuit you can convert the 12V dc in to the 220V Ac. In this circuit 4047 is use to generate the square wave of 50hz and amplify the current and then amplify the voltage by using the step transformer.
How to calculate transformer rating
The basic formula is P=VI and between input output of the transformer we have Power input = Power output
For example if we want a 220W output at 220V then we need 1A at the output. Then at the input we must have at least 18.3V at 12V because: 12V*18.3 = 220v*1
So you have to wind the step up transformer 12v to 220v but input winding must be capable to bear 20A.
Friday, March 29, 2013
Ultra Low Power 5V Regulator
The current drain of the regulator is minute compared with that of, say, a 78L05: at an input voltage of 9 V and open-circuit output, it is just under 50 µA. The circuit consists of a straightforward bandgap reference based on T1 and IC1, followed by an amplifier formed by IC2 and T1. The reference voltage is about 1.22 V, which is raised by IC2 to 5 V. The output voltage can be set to exactly 5 V with P1. The input voltage may lie between 6.5 V and 30 V. The maximum output current with the present configuration and component values as specified is about 10mA.
For optimum performance, T1a and T1b need to be identical, which is why a dual transistor Type MAT02 is used. Other types that may be used are the MAT01, SSM2210 or LM394. In principle, two standard BC transistors may be used, provided they are selected for identical threshold voltage. Circuits IC1 and IC2 are programmable op amps Type OP22. In the case of IC2 this has the benefit that the peak output current can be set readily by altering the supply current to the op amp with R9. The level of the current may be between 500 nA and 400 µA.
Bear in mind that a larger output current requires the use of a more highly rated output transistor. Filter R6-C1 prevents any spurious pulses reaching the input of IC2. Capacitor C2 improves the stability of the regulator, particularly with maximum pulse loading. Note that the circuit has a high resistance, so that it is advisable to house it in a screened enclosure to prevent undesired magnetic and electromagnetic interference being coupled to the circuit. The regulator was tested with a direct load current of 1 mA on which was superimposed a square-wave current of 10mA. The test results are summarized in the table, in which Ig represents the current drawn by the circuit.
readmore...
For optimum performance, T1a and T1b need to be identical, which is why a dual transistor Type MAT02 is used. Other types that may be used are the MAT01, SSM2210 or LM394. In principle, two standard BC transistors may be used, provided they are selected for identical threshold voltage. Circuits IC1 and IC2 are programmable op amps Type OP22. In the case of IC2 this has the benefit that the peak output current can be set readily by altering the supply current to the op amp with R9. The level of the current may be between 500 nA and 400 µA.
Bear in mind that a larger output current requires the use of a more highly rated output transistor. Filter R6-C1 prevents any spurious pulses reaching the input of IC2. Capacitor C2 improves the stability of the regulator, particularly with maximum pulse loading. Note that the circuit has a high resistance, so that it is advisable to house it in a screened enclosure to prevent undesired magnetic and electromagnetic interference being coupled to the circuit. The regulator was tested with a direct load current of 1 mA on which was superimposed a square-wave current of 10mA. The test results are summarized in the table, in which Ig represents the current drawn by the circuit.
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