Simple 3 Volts Car Adapter

This 3 volts Car Adapter circuit is based on a standard LT1074CT switching regulator IC. The schematic shows the LT1074CT used as a positive step-down or ‘buck’ converter. The ‘switcher’ is used to convert a +12-volt car battery voltage down to +3 volts for use with the personal hi-fi’s and handheld games for the author’s two boisterous children on long car journeys. Note at under ten years of age, children will rarely be hi-fi aficionado’s and are generally not concerned with any noise generated by the ‘switcher ‘circuit.

3 volts car adapter circuit diagram:

The circuit is connected to the car +12-V system via the cigarette lighter socket — is advisable to use a fused version of the cigarette lighter plug. The +12-V arrives on the board via screw- terminal block J2. Diode D2 provides a reverse voltage protection, while C3 decouples the input to the switcher IC.

The LT1074CT briskly switches the supply voltage on and off in response to the signal applied to its F/B input, to the extent that the average output voltage is at the required level. The values of potential divider resistors R1-R3 have been chosen to attenuate the output voltage so that there is 2.5 V at the F/B pin. The difference between the attenuated output voltage and the internal 2.5-V reference is used to control the modulation effect of the switcher.

Components R2 and C2 provide frequency stabilisation for the feedback loop. Inductor L1 along with the LT1074CT form the main switching components, while C1 provides decoupling for the output load. The 3-V output voltage is taken from screw terminal J1. With this circuit built, boxed up and installed in your car, you can look forward to possibly your first ‘quiet’ long car journey.

Author By: P. MARIAN

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USB DC Power Supply from Cigar Lighter Socket

The diagram shows the circuit of a versatile USB power socket that safely converts the 12V battery voltage into stable 5V. This circuit makes it possible to power/recharge any USB power-operated device, using in-dash board cigar lighter socket of your car.

The DC supply available from the cigar lighter socket is fed to an adjustable, three-pin regulator LM317L (IC1). Capacitor C1 buffers any disorder in the input supply. Resistors R1 and R2 regulate the output of IC1 to steady 5V, which is available at the ‘A’ type female USB socket. Red LED1 indicates the output status and zener diode ZD1 acts as a protector against high voltage.

USB Power Socket Circuit Diagram:

Assemble the circuit on a general-purpose PCB and enclose in a slim plastic cabinet along with the indicator and USB socket. While wiring the USB outlet, ensure correct polarity of the supply. For interconnection between the cigar plug pin and the device, use a long coil cord as shown in Fig. 2. Pin configuration of LM317L is shown in Fig. 3.

LM317 datasheet

Author by: P. MARIAN Source By: EFY

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Sealed Lead Acid Battery Charger Using LT3755

This Sealed Lead Acid Battery Charger is deigned using the LT3755 DC DC controller. The LT3755 is a DC DC controller designed to operate as a constant-current source and supports a wide input voltage range from 4.5 up to 40 volts and a can provide a maximum output voltage of 70 volts.

Sealed Lead Acid Battery Charger Circuit Diagram:

Also the LT3755 is a DC/DC controller can be used for any other applications where is needed a high efficiency ( like LED drivers ).

The main features of this Sealed Lead Acid (SLA) Battery Charger circuit are : adjustable frequency 100kHz to 1MHz ,low shutdown current:

The Sealed Lead Acid (SLA) Battery Charger based on the LT3755 require an input voltage between 8V to 40V and has VFLOAT = 13.5V and VCHARGE.

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Simple Battery Charger Controller Using UC3906

This UC3906 battery charger circuit controller contains all of the necessary circuitry to control the charge and hold cycle for sealed lead-acid batteries. The UC3906 battery charger circuit is specifically designed to provide the proper charging voltage and current determined by the temperature and state of charge of the battery.

Simple Battery Charger Controller Circuit Diagram:

The UC3906 battery charger circuit controller monitor and control both the output voltage and current of the charger through three separate charge states .

UC3906 has separate voltage loop and current limit amplifiers which regulate the output voltage and current levels in the charger by controlling the onboard driver.The charger circuit requires 18 to 22 volts DC input. Three optical ( LED ) indicators show the charge state . This IC is configured to provide three charge states:

• Bulk charge – the charger operates in a constant-current charge mode until the battery reaches the programmed full-charge voltage.
• Overcharge – when the voltage reaches the programmed full-charge voltage, the charger switches to overcharge mode to ‘top-off’ the battery.
• Float charge – when the current decreases to the minimum overcharge current, the charger enters the float charge mode.

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Universal Battery Charger Using by LM317

A very simple universal battery charger electronic project can be designed using the LM317 voltage regulator and some other electronic components . As you can see in this schematic circuit this charger has extreme few components , but is doing a very good job . When power is applied to the circuit the SCR1 is off, so there is no bias-current path to ground.

Universal Battery Charger Circuit Diagram:

The LM317 is connected to the battery through diode D1, limiting resistor R1, and bias resistor R2. The D1 diode is used to prevent the battery from discharging through the LED and the SCR when power is removed from the circuit. When LED1 is on, the circuit is in the voltage-regulating mode and when LED1 is off, the circuit is in the current-regulating mode.

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Simple USB Cell Phone Charge

Now you can charge your Mobile Phone from the USB outlet of PC. This simple usb cellphone charger circuit can give regulated 4.7 volts for charging the mobile phone. USB outlet can give 5 volts DC and 100 mA current which is sufficient for the slow charging of mobile phones.

USB Cell Phone Charger Circuit Diagram:

Most of the Mobile Phone battery is rated 3.6 volts at 1000 to 1300 mAh. These battery packs have 3 NiMh or Lithium cells having 1.2 volt rating. Usually the battery pack requires 4.5 volts and 300-500 mA current for fast charging. But low current charging is better to increase the efficiency of the battery. The circuit described here provides 4.7 regulated voltage and sufficient current for the slow charging of the mobile phone.

Transistor T1 is used to give the regulated output. Any medium power NPN transistor like CL100, BD139, TIP122 can be used. Zener diode ZD controls the output voltage and D1 protects the polarity of the output supply. Front end of the circuit should be connected to a A type USB plug. Connect a red wire to pin1 and black wire to pin 4 of the plug for easy polarity identification. Connect the output to a suitable charger pin to connect it with the mobile phone. After assembling the circuit, insert the USB plug into the socket and measure the output from the circuit. If the output is OK and polarity is correct, connect it with the mobile phone.

Note: If the polarity is incorrect, it will destroy the cellphone battery. So take extreme care.

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Simple USB Charger Doctor Unboxed

Recently I bought a little gizmo called as “USB Charger Doctor” from an online store. The little usb bus powered device features a passthrough usb connection to connect the usb source port and usb device, and a 7-segment LED display driven by an on-board microcontroller to indicate the voltage and current. As usual, I have an irresistible temptation to know how this device works, and just after 3 days from its arrival, I tried out the circuit surgery!

System Overview

The USB Charger Doctor holds an OTP microcontroller, Voltage and Current Sensors, and one 7-segment LED display unit. The internal electronics is powered by an onboard voltage regulator, which regulates the usb bus power to a stable 2.5 volt dc supply. Here is the system diagram of the USB Charger Doctor for your quick reference:

Why an OTP MCU? As designers look for ways to reduce the cost of their embedded systems without compromising the availability of peripherals or system performance, a potential solution to explore is the option of using one-time programmable (OTP) microcontrollers (MCUs) in their designs. OTP-based MCUs often provide the same peripherals and functionality as those found on flash-based devices, but at a reduced cost, or they can exceed the performance and functionality of flash-based MCUs at the same cost!

In the device, a “USB A-Male” connector is used for plugging into the usb port, and a “USB A-Female” socket for plugging the usb device into. Three digits of the 7-segment/4-digit red LED display shows the measurement value, and the last digit indicates volts (U) or amps (A). These voltage and current reading automatically alternates (between U and V) every 3 seconds or so. The 16-pin MCU – re-marked as 00F015 – is probably an HT series OTP (from Holtek). The current sensing element (Isense) is a 0.05R/2W shunt resistor, and a 2-resistor network (voltage divider) is wired as the voltage sensor (Vsense). The voltage regulator (Vreg) is built around the popular 3-pin adjustable shunt regulator chip TL431.

The LED display unit is a 12-pin common cathode 7-segment/4-digit type with the following pins:
Pin 1: E, Pin 2: D, Pin 3: DP, Pin 4: C, Pin 5: G, Pin 6: d4
Pin 7: B, Pin 8: d3, Pin 9: d2, Pin 10: F, Pin 11: A, Pin 12: d1
Where A to G are Segments, and d1 to d4 are Digits (cathodes) of the LED display unit. DP denotes Decimal Point. Part number of this display is CL3641AH.

Inside Electronics

Here is the indicative schematic circuit diagram of the usb charger doctor, drawn by me. Voltage measured at various points, when powered by my lab power supply (dialed to 5.0 Vdc), is also included in the drawing as a ready reckoner for all interested guys.

All the pins except 3, 4, 5, 12 and 13 of the 16-pin MCU (U2) are routed to the LED display unit – Pin 1 drives B, Pin 2 drives d3, etc. Pin 3 of the MCU is connected to the Vsense circuit, and Pin 4 is connected to the Isense circuit. Pin 5 is the ground and pin 13 is the VDD of the MCU. Note that the output from the Vreg circuit is also attached to the decimal point (pin 3) of the LED display. Have a look at the MCU to DISPLAY wiring, clearly shown in the following table:

Obviously, at the heart of this design is a low voltage (2.5V or less) MCU with built-in ADC and internal clock oscillator. This great design work amazes me because I already designed/published many digital voltmeter/ammeter circuits based on popular 5v/3.3v microcontrollers like AVR and PIC, but never tried an OTP MCU that works on < 2.5v, till date! Backwash

One week after this circuit surgery, I found another usb charger doctor circuit built around the Holtek OTP MCU HT46R064B (Enhanced A/D Type 8-Bit OTP MCU), circuit board and circuit diagram of which is shown below. Here, the major difference I noticed is in the power supply connections of the MCU; its pin 12 is connected to the +2.5V supply (VDD) rail. Besides, total 12 pins of the MCU are fully reserved for the display unit.

(pin notation of the display unit – CL3641AH)

OTP MCU Programming!

Flash MCUs are very familiar to us, but how to program a Holtek OTP MCU? It’s another question! The eWriterPro (from Holtek) can be used not only as a programming tool for all of Holtek’s OTP and Flash devices during the development stage but can also be used for small to medium volume production purposes. The eWriterPro must be used together with a corresponding eSocket according to the package type of the MCU that is to be programmed. Devices with the same package type require only a single eSocket, thus reducing the problem of changing different adaptors for different IC part numbers. More details: http://www.holtek.com/english/tech/tool/MainPage1.htm

Note: While every endeavor has been made to ensure accuracy of the contents of this article, some errors may exist. If you find any errors or if you have your own findings, please notify the author/site owner!

Author By: T.K. HAREENDRAN Source By: electroschematics.com

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General-Purpose NiCd Battery Charger

There is a wide variety of NiCd (nickel-cadmium) battery chargers on the market, but there are not many that can work from an in car 12 V cigar lighter. Such a charger would, for instance, be of interest to campers and caravanners who do not have a 230 V a.c. mains supply available. To satisfy the needs of these users, a charger could be designed for operation from the cigar lighter, but it is, of course, of far greater interest if it could also work from the domestic mains supply. Furthermore, it would also be very useful if a number of cells, say, 1 to 4, of different format could be charged simultaneously.

Lastly, another benefit would be if the charger would automatically switch off once the battery or cells have been charged fully. The charger described in this article does all that: it accommodates batteries or cells Type R6 and R14. Switching off after a period of 2 h 30 m, 5 h, or 10 h is arranged by 3-way switch S1. The 2 h 30 m period is for charging Type R6 batteries (1/2 charge), the 5 h period for fully charging Type R6 batteries or half charging Type R14 batteries, and the 10 h period for fully charging Type R14 batteries. Light-emitting diode D1 lights when charging is taking place. Charging after the set period has elapsed can be continued, if so desired, only by switching the supply off and then on again.

General-Purpose NiCd Battery Charger Circuit Diagram:

The time periods are determined by counters IC1 and IC2, Type 4060 and 4020 respectively. The 4060 has an integral oscillator, whose frequency is set to 932 Hz with preset P1 and the aid of a frequency meter. For various reasons, such as the values of the components used and parasitic elements, the oscillator itself operates at a slightly higher frequency – of the order of 1 kHz. The frequency of the signal at the wiper of P1 is divided by 214, so that the frequency of the signal at Q13 of IC1 is 0.056 Hz, equivalent to a pulse every 17.6 s. The signal at Q13 is applied to the input, pin 10, of IC2. When switch S1 is in position 2 h 5 m (output Q10 of IC2), the divisor should be 210 (1024).

However, contrary to what these figures indicate, the time period stops at half that at output Q10. To obtain a charging period of 2 h 30 m, that is, 9,000 seconds, which should correspond to half a period at output Q9 of IC2, the oscillator period must be 9000×2/16.7×106=1.073 ms, which corresponds to a frequency of 932 Hz as mentioned earlier. On power-on, only counter IC2 is reset, since an error of a few seconds that may arise in IC1 is of no significance. This arrangement simplifies the design. When the time set has elapsed, that is, charging is finished, diode D1 goes out.

The charging current is fixed by darlington transistor T3, which is a classical design of a current source with negative feedback. The transistor tends to hold its emitter potential at 1.3 V, but this requires the aid of a zener diode, D2. In this type of design, the thermal stability is, in fact, totally acceptable, because the temperature of the zener diode, in view of the small current this draws and its consequent low temperature rise, hardly affects the charging current Transistor T1 is either on or off and serves to power the on/off indicator LED. It is needed to prevent an overload on the output of counter IC1 if this would be required to absorb the total current (about 7mA) drawn by the diode.

Transistor T2 discontinues the charging when the time set by S1 has elapsed by earthing the base of darlington T3. Diodes D3–D14 are connected in threesomes across the terminals of the batteries to be charged: D3–D5 across those of battery Bt1, D6–D8 across those of Bt2, and so on. Diode D15 prevents the batteries to be charged from being discharged when the supply fails. When the charger is used in a vehicle, additional precautions should be taken to ensure that any spurious surges on the vehicle power lines do not adversely affect the charger’ s operation. The battery holder should be one that can accommodate four size R6 (AM3; MN1500; SP/HP7; mignon) or R14 AM2; MN1400; SP/HP11; baby) batteries.

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Simple 9V Automatic Battery NiCd Charger

The only thing to do is connect the battery and press the 'Start' button. When the discharge cycle is finished the circuit switches over to charge for 15 hours. After the 15 hours the circuits maintains a trickle charge to keep the battery 'topped-up'.

Before I go into the schematic details I like to explain some of the component descriptions in the schematic. Jan Hamer lives in the Netherlands and so the circuit details are based on european standards.

9V Automatic Battery NiCd Charger Circuit Diagram:

120E, 150E, etc. The 'E' just stands for Ohms so 120 ohm, 150 ohm. The original circuit specified the HEF type of cmos IC's which are not readily available in most of Canada. So just get any other type of CMOS chip like the MC4011, MC4020, MC4047 from Motorola. Any other type will do fine too. The BC548B is replaceble by a NTE123AP (NOTE: make sure it is the 'AP' type, the regular NTE123A is a total different transistor), ECG123AP, and the 2N3904 will work also. Watch for the correct pin locations since the BCE may be reversed with this european type. The LM317T is a TO-220 type and replaceble with a ECG956 or NTE956. The LM339N can be replaced with a ECG834 or NTE834

Although this circuit looks quite impressive and maybe a bit difficult it is certainly not difficult to understand. The circuit needs to be hooked-up to a DC supply voltage of between 16.5 and max 17.5 volt, otherwise the CMOS IC's will go defective. Because I didn't feel like to design a seperate powersupply for this circuit I connected it to my fully adjustable bench top powersupply.

First we connect a 'to-be-charged' 9-volt nicad battery to the appropriate connections. Then hook it up to the powersupply. Upon connection the 1nF capacitor starts up the two RS Flip-Flops formed by IC1a, IC1b, IC1c, IC1d, and pulls pins 3 and 10 'high' and pins 4 and 11 'low'. The clock pulses are created by the free-running multivibrator IC4. IC4's frequency is determined by the 10uF capacitors, the 220K resistor and the 100K trimpot. The clock runs continuesly but the counter behind, IC5, is not counting yet because pin 11 (the master-reset) is kept high. When the 'START' button is pressed, output pin 4 from IC1a goes high and biases TR4, which is made visible by the Red LED (D9) which remains lit. The NiCad is now being discharged via this transistor and the 100 ohm resistor.

The 10K trimpot (at the right of the diagram) is adjusted in such a way that when the battery voltage dips below 7 volt, the output of IC3 goes LOW and the output pin 11 of IC1a HIGH. At hte same time the output pin 10 of IC1d goes LOW, and the red LED turns off.

Because output pin 11 went HIGH the green LED (D8) lights up and at the same time the voltage level rises causing the battery to be charged. The charge-current is determined by the 120 ohm, 150 ohm, and the trimpot of 1K, at the right side of IC2. Actually we could have used one resistor, but the output voltage of different brands for IC2 may differ, by about 1.25 volt.

Because the charging current is devided by value of the resistors, with the trimpot the current can be adjusted to the correct value of your own 9-volt NiCad. (In my case, the battery is a 140 mA type, so the charge current should be adjusted for 14 mA (c/0.1).

At the same time the LOW of output pin 10 from IC1d starts the counter of the clock. On pin 9 of IC5 appear pulses which light up the red LED. This is implemented for two reasons, the clock-frequency can, with the 100K trimpot, be adjusted to the correct value; the red LED has to come ON for 6.59 seconds and for the same duration going OFF and except for that fact the green LED, who indicates the charge current, can be checked if the total charge-time is correct.

When the counter has reached 8192 pulses ( x 6.59 = 53985.28 sec = 14.99 hours) the output pin 3 of IC5 goes high again, transistor Tr1 activates and resets the two flip-flops to the start position.

The charging process stops and goes over to trickle charge via the 10K resistor and the D2 diode and keeps the battery topped-up.

The adjustments of the project are really very simple and nothing to worry about. Turn the walker of the 10K pot in the direction of the 12K resistor, ground connection point of 10K resistor/diode D2, like the adjustment pin of IC2, apply a voltage of 7-volt to the battery connection terminals, switch the power ON and slowly turn the pot backward until the greeen LED starts to light up. Switch OFF the power and take away the connections you made to make the adjustment.

Insert an amp-meter between the battery and the output connection and again switch the power ON. The battery will, in case it is not completely empty, totally discharged (to a safe level) and as soon as the 7 volt margin is reached goes over to the charge cycle. The charge current is at this time adjusted via the 1K trimpot (which is connected in series with the 150 Ohm resistor and in parallel with the 120 ohm resistor) accurately to the desired value.

Addendum: It is strongly recommended to include small 100nF ceramic capacitors over the powersupply lines feeding EACH CMOS IC to keep possible interference to a negliable value.

Author: Jan Hamer

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Simple Solar Cell Array Charger with Regulator

The circuit consists of an oscillator, a DC-DC step-up or ‘boost’ converter and a regulator that pro-vides regulation of the output voltage.The oscillator is built around a hex Schmitt trigger inverter IC, the 40106B, one resistor, R1, inserted between the input and the output of one of the gates in the 40106 to supply charge to C3. Depending on the values of resistor R1 and capacitor C3 you’re using in the circuit, the oscillator will operate at different frequencies, but a frequency below 100 kHz is recommended.

Solar Cell Array Charger with Regulator circuit can be used to charge batteries from a solar cell array.

By consequence, the oscillator frequency should not exceed the maximum ripple frequency of capacitor C2 connected on the output. C2 should be an electrolytic capacitor with a DC working voltage larger than the desired output voltage. Besides, it should have a low ESR (equivalent series resistance).

Solar Cell Array Charger with Regulator Circuit Diagram:

IC1A is used as a buffer, ensuring that the oscillator sees a light, fairly constant load and so guaranteeing that the output frequency remains stable (within limits, of course). VCC of the Schmitt trigger can be connected directly to the battery charged, provided the charged batter y voltage does not exceed the max. or min. limits of the Schmitt trigger’s supply voltage. This ensures the Schmitt trigger can operate even if little power is obtained from the solar cell array.

When transistor T2 is turned on, (output from oscillator buffer IC1A is high), a collector current flows through inductor L1 which stores the energy as a magnetic field and creates a negative voltage VL1. When transistor T2 is switched off, (output from oscillator buffer IC1A is low), the negative voltage VL1 switches polarity and adds to the voltage from the solar cell array. Consequently, current will now flow trough the inductor coil L1 via diode D1 to the load (capacitor C2 and possibly the battery), irrespective of the output voltage level.

Capacitor C2 and/or the battery will then be charged. So, in the steady state the out-put voltage is higher than the input voltage and the coil voltage VL1 is negative, which leads to a linear drop in the current flowing through the coil. In this phase, energy is again transferred from the coils to the out-put. Transistor T2 is turned on again and the process is repeated. A type BC337 (or 2N2222) is suggested for T2 as it achieves a high switching frequency. Inductor L1 should have a saturation current larger than the peak current; have a core material like ferrite (i.e. high-frequency) and low-resistance. Diode D1 should be able to sustain a forward current larger than the maxi-mum anticipated current from the source. It should also exhibit a small forward drop and a reverse voltage spec that’s higher than the output voltage. If you can find an equivalent Schottky diode in the junk box, do feel free to use it.

The most important function of the shunt regulator around T1 is to protect the batteries from taking damage due to overcharging. Besides, it allows the output voltage to be regulated. Low-value resistor R3 is switched in parallel with the solar cell array by T1 so that the current from the solar cell array flows through it. Zener diode D2 is of course essential in this circuit as its zener voltage limits the output voltage when T1 should be turned on, connecting the solar cell array to ground via R3. In this way, there is no input voltage to the boost converter and the battery cannot be overcharged.

Sealed lead-acid (SLA) batteries with a liquid electrolyte produce gas when over-charged, which can ultimately result in damage to the battery. So, it’s important to choose the right value for zener diode D2. Special lead-acid batteries for solar use are available, with improved charge-discharge cycle reliability and lower self-discharge than commercially-available automotive batteries.

Finally, never measure directly on the out-put without a load connected the ripple current can damage your voltmeter (unless it’s a 1948 AVO mk2).

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Solar Battery Charger with LM317

This is a solar panel battery charger schematic for AA and AAA rechargeable batteries. A small solar panel would be very good as a source of voltage charger. Building a solar AA battery charger only requires a few components and a simple construction. Solar panels should be well adapted to the battery to be charged or the battery may be overcharged.

Solar Battery Charger with LM317 Circuit Diagram:

 
If you want to charge batteries with different capacities, then you need to change the solar panels. Since this is a simple solar battery charger that does not automatically turn off when the battery is full. So we need to maintain the charging current is low enough that will not damage the battery even when they are fully charged. An LM317T voltage regulator chip that can be used with a suitable resistor to regulate current. See solar AA battery charger.

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9V Automatic Battery NiCd Charger

The only thing to do is connect the battery and press the 'Start' button. When the discharge cycle is finished the circuit switches over to charge for 15 hours. After the 15 hours the circuits maintains a trickle charge to keep the battery 'topped-up.

 Before I go into the schematic details I like to explain some of the component descriptions in the schematic. Jan Hamer lives in the Netherlands and so the circuit details are based on european standards.

 9V Automatic Battery NiCd Charger Circuit Diagram:

120E, 150E, etc. The 'E' just stands for Ohms so 120 ohm, 150 ohm. The original circuit specified the HEF type of cmos IC's which are not readily available in most of Canada. So just get any other type of CMOS chip like the MC4011, MC4020, MC4047 from Motorola. Any other type will do fine too. The BC548B is replaceble by a NTE123AP (NOTE: make sure it is the 'AP' type, the regular NTE123A is a total different transistor), ECG123AP, and the 2N3904 will work also. Watch for the correct pin locations since the BCE may be reversed with this european type. The LM317T is a TO-220 type and replaceble with a ECG956 or NTE956. The LM339N can be replaced with a ECG834 or NTE834

Although this circuit looks quite impressive and maybe a bit difficult it is certainly not difficult to understand. The circuit needs to be hooked-up to a DC supply voltage of between 16.5 and max 17.5 volt, otherwise the CMOS IC's will go defective. Because I didn't feel like to design a seperate powersupply for this circuit I connected it to my fully adjustable bench top powersupply.

First we connect a 'to-be-charged' 9-volt nicad battery to the appropriate connections. Then hook it up to the powersupply. Upon connection the 1nF capacitor starts up the two RS Flip-Flops formed by IC1a, IC1b, IC1c, IC1d, and pulls pins 3 and 10 'high' and pins 4 and 11 'low'. The clock pulses are created by the free-running multivibrator IC4. IC4's frequency is determined by the 10uF capacitors, the 220K resistor and the 100K trimpot. The clock runs continuesly but the counter behind, IC5, is not counting yet because pin 11 (the master-reset) is kept high. When the 'START' button is pressed, output pin 4 from IC1a goes high and biases TR4, which is made visible by the Red LED (D9) which remains lit. The NiCad is now being discharged via this transistor and the 100 ohm resistor.

The 10K trimpot (at the right of the diagram) is adjusted in such a way that when the battery voltage dips below 7 volt, the output of IC3 goes LOW and the output pin 11 of IC1a HIGH. At hte same time the output pin 10 of IC1d goes LOW, and the red LED turns off.

Because output pin 11 went HIGH the green LED (D8) lights up and at the same time the voltage level rises causing the battery to be charged. The charge-current is determined by the 120 ohm, 150 ohm, and the trimpot of 1K, at the right side of IC2. Actually we could have used one resistor, but the output voltage of different brands for IC2 may differ, by about 1.25 volt.

Because the charging current is devided by value of the resistors, with the trimpot the current can be adjusted to the correct value of your own 9-volt NiCad. (In my case, the battery is a 140 mA type, so the charge current should be adjusted for 14 mA (c/0.1).

At the same time the LOW of output pin 10 from IC1d starts the counter of the clock. On pin 9 of IC5 appear pulses which light up the red LED. This is implemented for two reasons, the clock-frequency can, with the 100K trimpot, be adjusted to the correct value; the red LED has to come ON for 6.59 seconds and for the same duration going OFF and except for that fact the green LED, who indicates the charge current, can be checked if the total charge-time is correct.

When the counter has reached 8192 pulses ( x 6.59 = 53985.28 sec = 14.99 hours) the output pin 3 of IC5 goes high again, transistor Tr1 activates and resets the two flip-flops to the start position.

The charging process stops and goes over to trickle charge via the 10K resistor and the D2 diode and keeps the battery topped-up.

The adjustments of the project are really very simple and nothing to worry about. Turn the walker of the 10K pot in the direction of the 12K resistor, ground connection point of 10K resistor/diode D2, like the adjustment pin of IC2, apply a voltage of 7-volt to the battery connection terminals, switch the power ON and slowly turn the pot backward until the greeen LED starts to light up. Switch OFF the power and take away the connections you made to make the adjustment.

Insert an amp-meter between the battery and the output connection and again switch the power ON. The battery will, in case it is not completely empty, totally discharged (to a safe level) and as soon as the 7 volt margin is reached goes over to the charge cycle. The charge current is at this time adjusted via the 1K trimpot (which is connected in series with the 150 Ohm resistor and in parallel with the 120 ohm resistor) accurately to the desired value.

Addendum: It is strongly recommended to include small 100nF ceramic capacitors over the powersupply lines feeding EACH CMOS IC to keep possible interference to a negliable value.

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Wind Charger Using LTC1042

It is very simple electronic circuit project of wind charger circuit using the LTC1042 monolithic CMOS window comparator, manufactured by Linear Technology INC. 

Wind Charger Using LTC1042 Circuit Diagram:

 
This Wind charger circuit electronic project use the wind power to produce the energy required to charge Ni-Cd or Lead Acid batteries. As you can see in the circuit diagram, you will need a 12 volts generator, a dc motor can be used (the output voltage is proportional to its rpm). As you can see in the circuit diagram, are connected two batteries: a 4.5 volts Ni-Cd and a 12 volts Lead Acid battery.

If generator voltage output is below 13.8V, the control circuit is active and the NiCad battery is charging through the LM334 current source (the lead acid battery is not being charged). If the generator voltage output is between 13.8V and 15.1V, the 12V lead acid battery is being charged at about a 1A/hour rate (limited by the power FET).

If generator voltage exceeds 15.1V (a condition caused by excessive wind speed or 12V battery being fully charged) then a fixed load is connected thus limiting the generator RPM to prevent damage.

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Step-Down Battery Charger From Solar Panel

This is very simple and low-cost Electronic Circuit Project of step-down battery charger from solar panel. Using the LT3652 step-down battery charger which operates over a wide range input voltage can be build a very simple solar charger. The LT3652 provides a constant-current constant-voltage charge characteristic with maximum charge current externally programmable up to 2A. The desired output voltage can be up to 14.4V, programmed with a resistor divider.

Step-Down Battery Charger From Solar Panel Circuit Diagram:

When the LT3652 is powered by a solar panel, the input regulation loop is used to maintain the panel at peak output power. The LT3652 can be configured to stop charging when charge current falls below 1/10 of the maximum programmed and an new charging cycle starts if the battery voltage falls 2.5% below the programmed float voltage. When the charging process is over the LT3652 enters in a low-current mode (85μA standby mode).

The LT3652 can be also programmed to stop the charging process after a desired time.

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Charger Extends Lead-Acid Battery Life

Here is simple electronic circuit project of charger extends lead-acid battery life.  The circuit furnishes an initial charging voltage of 2.5 V per cell at 25°C to rapidly charge a battery. The charging current decreases as the battery charges, and when the current drops to 180 mA, the charging circuit reduces the output voltage to 2.35 V per cell, floating the battery in a fully charged state.

Circuit Diagram:

This lower voltage prevents the battery from overcharging, which would shorten its life. The LM301A compares the voltage drop across R1 with an 18-mV reference set by R2. The comparator`s output controls the voltage regulator, forcing it to produce the lower float voltage when the battery-chaiging current passing through R1 drops below 180 mA. the 150-mV difference between the charge and float voltages is set by the ratio of R3 to R4. The LEDs show the state of the circuit.

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Low-cost L200 Charger

This circuit came about as the result of an  urgent need for a NiMH battery charger. No  suitable dedicated IC being immediately to  hand, the author pressed an L200 regulator and a 4.7 kΩ NTC thermistor into service.  Those components were enough to form the  basis of a charger with a cut-of f condition  based on cell temperature rise rather than  relying on the more common negative delta-V detection.

L200 Charger Circuit Diagram :

 
The circuit uses the L200 with the thermistor in the feedback loop. When ‘cold’ the  output volt age of the regulator is about 1.55 V per cell; when ‘warm’, at a cell temperature of about 35 °C to 40 °C, the out-put voltage is about 1.45 V per cell and the  thermistor has a resistance of about 3.3 kΩ.  This temperature sensing is enough to pre-vent the cells from being overcharged. P1  adjusts the charging voltage, and R2 limits  the charge current to 320 mA. The IC is fitted with a small 20 K/W heatsink as it dissipates around 1.2 watts in use.

The charger circuit can be connected permanently to the battery pa ck . Charging  starts when a ‘ wall wart ’ adaptor is connected to the input of the charger. The unregulated 12 V supply used by the author  delivered an open- circuit voltage of 18 V,  dropping to 14 V under load. Even though  the charge voltage is reduced when charging is complete, the cells should not be left  permanently on charge.

The author uses the circuit to charge the battery in a torch. After three years and some 150  charge cycles the cells are showing no signs of losing any capacity.

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Simple Fast Battery Charger Using LTC4012

Here is very simple but very fast battery charger electronic circuit diagram project, the  Linear Technology Corporation introduces the LTC4012, LTC4012-1 and LTC4012-2, fast-charge 4A capable high efficiency switchmode battery charger controllers for multiple battery chemistries. The LTC4012 supports Li-Ion Polymer, NiMH, NiCd and sealed lead acid battery chemistries in single and multicell configurations. The LTC4012 offers an adjustable battery termination voltage, while the LTC4012-1 and LTC4012-2 utilize a programmable internal resistor divider to charge from 1 to 4 series Lithium cells at multiples of 4.1V and 4.2V, respectively.

Circuit Diagram:

Main features of charger LTC4012 family chips are : Efficient 550kHz Synchronous Buck PWM Topology , ±0.5% Output Float Voltage Accuracy , Programmable Charge Current: 4% Accuracy , Programmable AC Adapter Current Limit , No Audible Noise with Ceramic Capacitors , INFET Low Loss Ideal Diode PowerPath™ Control , Wide Input Voltage Range: 6V to 28V , Wide Output Voltage Range: 2V to 28V , Indicator Outputs for AC Adapter Present, Charging,C/10 Current Detection and Input Current Limiting , Analog Charge Current Monitor , Micropower Shutdown .

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Battery Charger using LM317

This Battery Charger Electronic circuit Project An LM317 voltage regulator is configured as a constant-current source. It is used to supply the 50 mA charging current to S01-S06, an array of AA-cell battery holders. Each of the battery holders is wired in series with an LED and its associated shunt resistor.

Battery charger using LM317 Circuit Diagram:

When the battery holder contains a battery, the LED glows during charging. Each battery holder/LED combination is paralleled by a 5.1-volt Zener diode. If the battery holder is empty, the Zener conducts the current around the holder.

A timing circuit prevents overcharging. When power is applied to the circuit, timing is initiated by IC2, a CD4541 oscillator/programmable timer. The output of IC2 is fed to Ql. When that output is high, the transistor is on, and the charging circuit is completed. When the output is low, the transistor is off, and the path to ground is interrupted. 

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Simple but Automatic Battery Charger

Normally, chargers available in the market do not have any sort of control except for a ro-tary switch that can select different tap-pings on a rheostat, to vary the charging current. This type of control is not adequate because of the irregular fluctuations in the mains supply, rendering the control ineffective.  A simple circuit intended for automatic charging of lead-acid batteries is presented here. It is flexible enough to be used for large capacity inverter batteries. Only the rating of transformer and power transistor needs to be increased. 

 

The circuit has been basically designed for a car battery (about 40 Ah rating), which could be used for lighting two 40W tube lights. The circuit includes Schmitt trigger relay driver,float charger,and battery voltage monitor sections.  The Schmitt trigger is incorporated to avoid relay chattering. It is designed for a window of about 1V. During charging, when the battery voltage increases be-yond 13.64V, the relay cuts off and the float charging section continues to work. When battery voltage goes below 11.66V, the relay is turned on and direct (fast) charging of the battery takes place at around 3A.  In the Schmitt trigger circuit, resistors R1 and R2 are used as a simple voltage divider (divide-by-2) to provide battery voltage sample to the inverting input terminal of IC1. The non-invert-ing input terminal of IC1 is used for reference input derived from the output of IC2 (7806), using the potentiometer arrangement of resistors R3 (18 kilo-ohm) and R4 (1 kilo-ohm). 

Automatic Battery Charger Circuit Diagram:

 

 

LED1 is connected across relay to indicate fast charging mode. Diodes D3 and D6 in the common leads of IC2 and IC3 respectively provide added protecion to the regulators.  The float charging section, comprising regulator 7812, transistors T3 and T4, and few other discrete components, becomes active when the battery volt-age goes above 13.64V (such that the relay RL1 is deenergised). In the energised state of the relay, the emitter and collector of transistor T4 remain shorted, and hence the float charger is ineffective and direct charging of battery takes place.

The reference terminal of regulator (IC3) is kept at 3.9V using LED2, LED3, and diode D6 in the common lead of IC3 to obtain the required regulated output (15.9V), in excess of its rated output, which is needed for proper operation of the circuit. This output voltage is fed to the base of transistor T3 (BC548), which along with transistor T4 (2N3055) forms a Darlington pair. You get 14.5V output at the emitter of transistor T4, but because of a drop in diode D7 you effectively get 13.8V at the positive terminal of the battery. When Schmitt trigger switches ‘on’ relay RL1, charging is at high current rate (boost mode). The fast charging path, starting from transformer X2, comprises diode D5, N/O contacts of relay RL1, and diode D7.

The circuit built around IC4 and IC5 is the voltage monitoring section that provides visual display of battery voltage level in bar graph like fashion. Regulator 7805 is used for generating reference voltage. Preset VR1 (20 kilo-ohm) can be used to adjust voltage levels as indicated in the circuit. Here also a pot meter arrangement using resistors R7, R8, and R9 is used as ‘divide by 3’ circuit to sample the battery voltage. When voltage is below 10V, the buzzer sounds to indicate that the safe dis-charge limit has been exceeded. Link

 

 

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Solar Powered Lamp

This is a very simple Electronic circuit diagram project of solar lamp garden circuit (solar loading) is presented in this schematic circuit. Sunlamps uses solar cells to charge two 600 mAh NiCd accumulator. It charges the battery and light on the LED at dusk, and will be off during daylight.

Solar Powered Lamp Circuit Diagram:

Light use eight solar cell of 0.45 V, a solar panel which will provide ~ 3.6 V when illuminated. The amount of voltage supplied solar cells must be greater than the battery charge voltage (~ 3.1V, 2.8 V + 0.3 V for Schottky diode). Solar cells will provide about 50mA under the influence of the sun and if it will use some batteries 500mah at least they will not be affected by overload.

Transistor T1 with photoresistor (LDR light dependent resistor) is used for sensing the level of illumination. Solar Cells should be puted in the solar lamp housing so that it can be properly illuminated by sun . The solar lamp illumination can be used to illuminate the court or of places that have access to direct sunlight day.

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