Auto Battery Charger

This auto battery charger uses no transformer, rectifier, or filter capacitors on the schematic. No reason why you cannot add these. This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the battery is fully charged, the circuit switches off and lights a LED, telling you that the cycle has finished.
Auto Battery Charger Schematic


A heatsink will be needed for this auto battery charger ( U1.)

Auto Battery Charger Parts List
Resistor
R1 500 Ohm 1/4 W
R2 3K 1/4 W
R3 1K 1/4 W
R4 15 Ohm 1/4 W
R5 230 Ohm 1/4 W
R6 15K 1/4 W
R7 0.2 Ohm 10 W
Capacitor
C1 0.1uF 25V Ceramic
C2 1uF 25V Electrolytic
C3 1000pF 25V Ceramic
Diode
D1 1N457
Transistor
Q1 2N2905 PNP
Regulator
U1 LM350
Op Amp
U2 LM301A
S1 Normally Open Push Button Switch
MISC Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output

To use the circuit, hook it up to a power supply/plug it in. Then, connect the battery to be charged to the output terminals. All you have to do now is push S1 (the “Start” switch), and wait for the circuit to finish


C1 6800uF 25V Electrolytic Capacitor
T1 3A 15V Transformer
BR1 5A 50V Bridge Rectifier 10A 50V Bridge Rectifier
S1 5A SPST Switch
F1 4A 250V Fuse

If you want to use the auto battery charger without having to provide an external power supply, use above circuit. The first time you use the circuit, you should check up on it every once and a while to make sure that it is working properly and the battery is not being over charged

Low Voltage monitor

This is a circuit which can be used to monitor batteries or other electric equipments current problems.Here that current will be indicated through the sound and through the LED.So you all can check your low volt equipments easily.

Parts:

U1 LM339 Voltage comparator IC
D1 1N5233B Zener Diode
D2 LED
R1, R3 1K 1/4W Resistor
R2 5K Pot
BZ1 Piezo Buzzer
MISC Board, wire, socket for IC

Note

# This circuit can be operated with 9v to 12v

High & Low voltage cut-off with delay& alarm

This straight forward circuit will protect electrical appliances from over voltage as well as under voltage.The circuit also produces an alarm when the power supply comes back.An ideal circuit for home to protect your valuable equipments from voltage fluctuations.The same circuit with some modifications can be used to make a automatic voltage stabilizer

When the mains voltage is in the normal level ,the voltage at the negative terminal of zener diode D4 will be less than 5.6 Volts.At this condition transistor T1 will not conduct.The same time voltage at the negative terminal of zener diode D5 will be greater than 5.6 and so the transistor T2 will be conducting.The relay will be activated and the green LED wil be glowing.

When the mains voltage is higher than the set limit the transistor T1 becomes conducting since the voltage at the negative terminal of D4 is greater than 5.6 V.At the same time transistor T2 will be non conducting which results in the deactivation of relay to cut the mains supply from load.When the mains voltage is less than the set limit transistors T1 & T2 becomes non conducting making the relay to de- activate and cut the load from mains.Ω

The timer NE555 is wired as a monostable multivibrator with a pulse width of 10ms.When the power comes back after a cut off a negative voltage is obtained at the trigger pin which triggers the IC NE555.The transistor T3 gets forward biased and it drives the buzzer to produce a beep as an indication of power resumption.Also the transistor T1 is made on which in turn makes T2 off.As a result the relay will remain de- activate for 10ms and this provides the sufficient delay and the equipment is protected from surge voltages.

Notes.

* To calibrate the circuit a autotransformer is needed.Connect the output of autotransformer to the transformer primary.
* Set the voltage to 260V and adjust VR1 to make the relay deactivated.
* Now set the autotransformer to 160V and adjust VR2 so that the relay is de-energized.
* VR3 can be used to vary the volume of buzzer.

li-on-battery-charger-via-usb

Description:

A USB port is a great power source for charging a single cell li-on battery. It is capable of supplying maximum 5.25V and 500 mA. The circuit above is a USB powered single cell li-on battery charger. LM3622 is used as the controller. This special purpose IC has a precise end-of-charge control and low battery leakage current about 200nA

Simple 5 Ampere Power Supply

Power supply is a must used circuits. Most of electronic devices which require DC voltage usually need a power supply. Some of them just need original power supply or battery, but some of circuits like Radio transmitter or amplifier needs high current output power supply.

This project is a simple and easy made 5 ampere power supply. To build this circuit, just follow the instruction below:

This is a fixed, but variable, power supply developed for ease of design and building. The power supply is capable of supplying almost 5A with the right components. The right components are a stable 5A transformer, bridge rectifier and a heatsink that can dissipate the excess power developed in this type of power supply. I have limited the current to just over 3A with a fuse, as I have found that, this in practice is about the maximum current that can be drawn before the system becomes too hot.

The circuit diagram is shown in Fig. 1, and as you can see, it really is a simple circuit.


Figure 2 show the diagramatic (pin side/inside view) view of IC1, and most of the other components, mounted on a large heatsink. It is important that the LM338K integrated circuit be insulated from the heatsink. No printed circuit board is needed as most of the components are mounted on the heatsink

The integrated circuit IC1, has all the active power supply control circuitry on board.
Output can be designed to be almost any value between 1.2V and the regulator’s limit of 35V. For the higher voltages, some changes would have to be made to the transformer, diode and filter capacitor circuitry.

Here is a small table to help you achieve the output voltage you need.

Vout New R1

1.5V 68 Ohm
3V 390 Ohm
4.5V 680 Ohm
6V 1K
7.2V 1.2K
9V 1.8K
12V 2.2K
15V 3K
20V 3.9K
24V 5.1K
28V 6K

This table is not meant to be highly accurate, but just to give an indication of the required resistance to replace R1. At higher output voltages, you may need to modify the resistance slightly to get a more accurate voltage output. Give this project a try, you will enjoy building and using it.

PARTS LIST:

Resistors:
1 X 270 ohm R2
1 X 470 ohm R3
1 X 2.7k ohm R1

Capacitors:
Mylar 160V
1 X 220n C3
Electolytic 25V
1 X 1uF C2
1 X 15000uF C1

Semiconductors:
1 X LM338K IC1
1 X Bridge Rectifier 5A

Miscellaneous:
1 X 100VA 15V transformer
1 X 3.15A fuse and fuse holder
1 X Red Led
Suitable Heatsink
Cabinet.

Info on some of the components used:




Enjoy building this simple but very effective 5 volt Power Supply.

Adjustable Power Supply with Charger Output

You can adjust the output voltage from 0V up to 12V with variable resistor R2. This circuit can handle a 1 ampere current. The 317 must have a heat sink. The charger output is 6V, you can use the charger to charge your mobile phone battery.
:

Electronic parts list:

Semiconductor:
LM 317 – 1pc
LED – 1pc
1N 4001 – 8pcs

Capacitors:
25V/470uF – 1pc
25V/10 uF – 1pc

Resistors:
1k, 1/2W – 1pc
220R, 1/2W – 1pc
5kR Potentiometer – 1pc

Others:
1Ampere, Multi-tap Transformer – 1pc
AC Chord – 1pc
Casing – 1pc
#22 Stranded Wire – 3m
Heatsink for TO220

Dual Regulated Power Supply

This power supply will stabilize the voltage, both the positive voltage and negative voltage. IC 7815 will stabilize positive voltage +15V and IC 7915 will stabilize the negative voltage -15V.

If you need stabilized 15 V output, you should choose transformer output around 18-24V AC and use IC 7815 and 7915. If you need stabilized 6V output, you sould choose transformer output arround 9V-15V and use IC 7806/7906.

High Current Power Supply

This power supply circuit can supply high current for your electronic project. Transistor 2N3055 is the main component which will increase the current level.

Part Total Qty. Description/Value
R1 1 680 Ohm 1/4 Watt Resistor
C1 1 20,000 – 50,000uF 20-40 Volt Capacitor
C2, C3 2 100uF 50 Volt Capacitor
C4 1 0.1uF 50 Volt Capacitor
C5 1 0.01uF 50 Volt Capacitor
D1 1 Zener Diode (See Notes)
Q1 1 2N3055 Or Other (See Notes)
T1 1 Transformer (See Notes)
BR1 1 Bridge Rectifier (See Notes)
S1 1 SPST 250 VAC 10 A Switch
MISC 1 Case, Line Cord, Heatsink For Q1, Binding Posts For Output

Notes:

1. D1 should be rated at about one volt higher than then desired output of the supply. A half watt diode will do.

2. Q1 can be a transistor similar to the 2N3055. I chose the 2N3055 for it’s availability and power handling (150 watts).

3. T1 should be about 5 volts higher than the desired output of the supply, and rated for about one amp more of current. The voltage overhead is required by the regulator section. The extra current is to keep the transformer from over heating.

4. The choice of BR1 will depend on the voltage and current of your transformer. The rectifier should be rated for 50 volts more than the transformer, and 5 amps more than the transformer.

5. The value of R1 will be smaller when supplying high currents. Expiriment until you get what you need.

6. Heatsink and fans are absolutely necessary!

12VDC to 240VDC Inverter circuit

Above circuit is an inverter circuit which will convert 12-14V DC to become 240V DC. For AC output, you need to remove the bridge diode and C5.

500w Low Cost 12v To 220v Inverter electronic circuit diagram

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.

2n3055 Power Amplifier 60w electronic circuit diagram

Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can build it almost of the components, which you find at home. The and transistors can be any NPN type power transistor, but do not use Darlington types... The output power is around 60W.

Some comments:

- capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequncies are getting louder.
- capacitor C2 regulates the higher frequencies (treble), as the capacitance grows, the higher frequencies are getting quiter.
- this is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500Ω trimmer resistor. As this current incrases, the sound of the amplifier gets better, but the end transistors are more heating. But if this current decrases, the transistors are not heating so much, but the sound gets worse...

USB Coin/Button Cell Battery Charger

USB Coin/Button Cell Battery Charger
I have designed many small footprint PIC projects (such as, pocket watches and wristwatches) but I cannot make them really portable. To make them portable, I need small power sources. Of course, Coin Cell battery would be the smallest DC source that I can buy. The problem is that a Lithium button cell provides 3 V. which is not enough to drive my projects. I thought about using DC-DC step-up converter to boost 3 V. to 5 V. However, it's a little bit complex to add DC-DC converter to the projects. Moreover, my projects consume a lot of power as they consist of many LEDs, a button battery will not last for a day. So, I stopped my think at that point.

Just recently, I have found a rechargeable coin cell battery at Sparkfun.com. It provides 3.7 V. at 200mAh. I don't know that my projects will work at 3.7 V. or not. But, I want to give it a try. For portability, I want to charge the battery from my computer's USB port. So, I designed a USB coin cell battery + charger breakout board. Like many simple battery charger, I use MAX 1555 as the controller of the charger

6v-to-12vdc-converter-schematic

This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages.

Parts
Part Total Qty. Description Substitutions
R1, R4 2 2.2K 1/4W Resistor
R2, R3 2 4.7K 1/4W Resistor
R5 1 1K 1/4W Resistor
R6 1 1.5K 1/4W Resistor
R7 1 33K 1/4W Resistor
R8 1 10K 1/4W Resistor
C1,C2 2 0.1uF Ceramic Disc Capacitor
C3 1 470uF 25V Electrolytic Capcitor
D1 1 1N914 Diode
D2 1 1N4004 Diode
D3 1 12V 400mW Zener Diode
Q1, Q2, Q4 3 BC547 NPN Transistor
Q3 1 BD679 NPN Transistor
L1 1 See Notes
MISC 1 Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

Notes

1. L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.

2. Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.

3. You can use a larger value for C3 to provide better filtering.

4. The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V

Switching Power Supply 13.8V 40A

Switching Power Supply 13.8V 40A


This power supply circuit produces 13.8V regulated to better than 1%, at a continuous load current of up to 40A. It has current limiting, making it appropriate for direct connection to a 12V backup battery. If the current limit potentiometer is turned up, the power supply can deliver up to 60A on an intermittent basis, while maintaining regulation. No minimum load is required. The ripple on the output is about 20mV, and the efficiency is 88%

Linear Power Supply 13.8V 20A

Linear Power Supply 13.8V 20A

This linear power supplycircuit has a transformer that steps down the line voltage to some voltage that is higher than what will be required at the regulated output. Then a rectifier and a filter capacitor transform the low voltage AC into a moderately filtered DC that still is unregulated and has some ripple. Finally, a regulating circuit "burns off" the excess voltage, leaving only the exact amount desired at the output, typically 13.8V for communication equipment.

Variable Power Supply 1-25V LM317

Variable Power Supply 1-25V LM317

This is a variable power supply circuit uses LM317. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It's ideal for just about any application. Since LM317 is protected against short-circuit, no fuse is necessary.



Although LM317 regulated IC is capable of delivering up to 37V, the circuit pictured here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink.

Regulated Power Supply 78xx

Regulated Power Supply 78xx

Here's an universal circuit of all the voltage regulator ICs, the 78xx family is by far the most established. Not surprisingly! It's difficult to get performance this good with so few outside components necessary.



The 78xx family just like the famous LM317, incorporates automatic shutdown in case of overheating. You can get up to 1.5A of current with a suitable heat sink. No fuse is required

24VDC Power Supply with maximum Current 5A

24 VDC Power Supply with maximum Current 5A

Here's a 24 VDC power supply circuit with voltage input 20-30 Vcc. This power supply produces voltage output 13.5 VDC maximum current 5A.

The features capability of this 24 VDC power supply are protection against short circuit current, over temperature, over output voltage, and inversion polarity.



See 24 VDC Power Supply schematic below.



Parts list of the 24 VDC Power Supply
C1 = 33uF 35V
C2 = 10 nf 50V
C3 = 10nF 50V
C4 = 33uF 35V
D1 = 1N5400
D2-D3 = 1N4004
D4 = Zener Diode 15V 5W
IC1 = IC2 = 7812
Fuse = 5A

Uninterruptible Alarm Power Supply

Uninterruptible Alarm Power Supply

Although this Power Supply was designed for the Modular Burglar Alarm - it has other applications. It provides an output of 12-volts - at a current of up to 1-amp. In the event of a mains failure - the back-up battery takes over immediately. And when mains power is restored - the battery recharges automatically.

The 7805 needs the larger heatsink because it has to dissipate a lot of energy - especially when called upon to recharge a flat battery. Its heatsink is at 9v1 - and must NOT be connected to ground. The 7812 never has to dissipate more than 2-watts - so its heatsink can be smaller.

Many of the components, which are shown lying flat on the board, are actually mounted standing upright. The links are bare copper wire on the component side of the board. The heatsinks are folded strips of aluminium, about 2mm thick. Use a well-insulated panel mounted fuse holder for the mains supply to the transformer - and fit it with a 1-amp fuse.

Use a genuine alarm type back-up battery. They are maintenance-free. Their terminals can be held at 13v8 for many years - with no apparent ill effects. They have a life expectancy of about five years. However, they tend not to recover from a very deep discharge. If you wish - you can use a smaller or larger capacity battery

Variable DC Power Supply 5-15V

Variable DC Power Supply 5-15V

This is a variable DC power supply that is similar I used to power my FM Transmitter. After suffering long problems with mains hum, this design using a pi filtered C-L-C approach. This circuit offers excellent ripple rejection.

See at the above schematic, the specific inductance of the ferrite (core)is important. A core should be chosen to work within the specific frequency as stated by the manufacturer. L1 is a powder core and has 32 turns of 0.75mm wire.

The transformer of this Variable DC Power Supply has a 240V primary and has a secondary rated 24V at 2A. The bridge rectifier contains 4 diodes, their current rating needs to be high with respect to the transformers output current; if not the current may damage the diodes. I used MR751 which is rated 6 amps, but another good choice is 1N5400. C1 is the mainfiltering capacitor, the supply is further smoothed by the combination of L1 and C3. C2 and C4 are decoupling capacitors; their action further reduce ripple factor.

The regulator, U1 utilizes the action of zener diode ZD1 which is in parallel with the potentiometer, R1. The tuning action of R1 produces a variable regulator output. The output voltage is variable from the regulator output to the regulator output plus the zener voltage. E.G. A 7805 regulator and 10V zener give an output adjustable from 5 to 15 Volts. The regulator may be changed to provide different output voltages as may the zener. the zener should be rated a minimum of 1.3 Watts. All the parts should be available at local electronic shops.

Parts List of the Variable DC Power Supply:
T1 Transformer 10:1 Secondary 24V @ 2A
BR1 Bridge Rectifier 50V PIV 2A rating
C1 4700u (35V)
C2 0.001u
C3 2200u (35V)
C4 0.001u
C5 4.7u (25)
C6 0.01u
R1 10k potentiometer
L1 see text
U1 7805 N.B. This may be changed for different output voltages e.g. 7812 for higher output voltage
ZD1 15V zener @ 1.3W