Simple Auto Turn Off Battery Charger Circuit Diagram

This Auto Turn-Off Battery Charger Circuit Diagram for series-connected 4-cell AA batteries automatically disconnects from mains to stop charging when the batteries are fully charged. It can be used to charge partially discharged cells as well. The circuit is simple and can be divided into AC-to-DC converter, relay driver and charging sections. In the AC-to-DC converter section, transformer X1 steps down mains 230V AC to 9V AC at 750 mA, which is rectified by a full-wave rectifier comprising diodes D1 through D4 and filtered by capacitor C1. Regulator IC LM317 (IC1) provides the required 12V DC charging voltage.



 Auto Turn-Off Battery Charger Circuit Diagram

When you press switch S1 momentarily, the charger starts operating and the power-on LED1 glows to indicate that the charger is ‘on.’ The relay driver section uses pnp transistors T1, T2 and T3 (each BC558) to energise electromagnetic relay RL1. Relay RL1 is connected to the collector of transistor T1. Transistor T1 is driven by pnp transistor T2, which, in turn, is driven by pnp transistor T3. Resistor R4 (10-ohm, 0.5W) is connected between the emitter and base of transistor T3.

When a current of over 65 mA flows through the 12V line, it causes a voltage drop of about 650 mV across resistor R4 to drive transistor T3 and cut off transistor T2. This, in turn, turns transistor T1 ‘on’ to energise relay RL1.


Now even if the pushbutton is released, mains is still available to the primary of the transformer through its normally open (N/O) contacts.  In the charging section, regulator IC1 is biased to give about 7.35V. Preset VR1 is used for adjusting the bias voltage. Diode D6 connected between the output of IC1 and battery limits the output voltage to about 6.7V, which is used for charging the battery.  Pushing switch S1 latches relay RL1 and the battery cells start charging. As the voltage per cell increases beyond 1.3V, the voltage drop across resistor R4 starts decreasing. When it falls below 650 mV, transistor T3 cuts off to drive transistor T2 and, in turn, cuts off transistor T3.


As a result, relay RL1 de-energises to cut off the charger and red LED1 turns off.  You may determine the charging voltage depending on the NiCd cell specifications by the manufacturer. Here, we’ve set the charging voltage at 7.35V for four 1.5V cells. Nowadays, 700mAH cells are available in the market, which can be charged at 70 mA for 10 hours. The open-circuit voltage is about 1.3V. The shut-off voltage point is determined by charging the four cells fully (at 70 mA for 14 hours). After measuring the output voltage, add the diode drop (about 0.65V) and bias LM317 accordingly.

Author : Y.M. Anandavardhana

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Auto Anti Hijack Alarm Circuit Diagram

This Auto Anti-Hijack Alarm Circuit Diagram was designed primarily for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on - the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the Siren will sound.

Where it differs from the first two alarms - is in what happens next. Im obliged to Victor Montanez from the USA who suggested that the engine cut-out should not operate - until the vehicle comes to a stop. That way - the engine will not fail suddenly or unexpectedly. And the hijacker will retain control.

I havent been able to implement Victors excellent suggestion completely - because I couldnt think of a simple, reliable and universally applicable way of sensing when the vehicle has come to a stop.

Instead - I have postponed engine failure until the ignition is switched off. Once the thief turns off the ignition - the engine will not re-start. Clearly - there is no certainty as to when this will occur. But I think it will occur sooner rather than later. Because theres a strong possibility that the hijacker will turn off the ignition - in an attempt to silence the siren. 

 Auto Anti-Hijack Alarm Circuit Diagram

As well as acting as a Hijack Alarm - this circuit offers some added protection. Like the Enhanced Hijack Alarm - it incorporates Jeff Chias suggestion. That is - every time the ignition is switched on - the alarm will trip. So it will protect the vehicle whenever you leave it unattended with the ignition switched off - even overnight in your driveway.

Importance

Before fitting this or any other engine cut-out to your vehicle - carefully consider both the safety implications of its possible failure - and the legal consequences of installing a device that could cause an accident. If you decide to proceed - you will need to use the highest standards of materials and workmanship.

Notes

Youre going to trip this alarm unintentionally. When you do - the LED will light and the Buzzer will give a short beep. The length of the beep is determined by C4. Its purpose is to alert you to the need to push the reset button. When you push the button - the LED will switch-off. Its purpose is to reassure you that the alarm has in fact reset. 

If the reset button is not pressed then - about 3 minutes later - both the Siren and the Buzzer will sound continuously. The length of the delay is set by R8 & C5. For extra effect - fit a second siren inside the vehicle. With enough noise going on - you may feel that its unnecessary to fit the engine cut-out. In which case - you can leave out C7, D8, R12, R13, Ty1 & Ry2.

When the ignition is switched on - C3 & R4 are responsible for tripping the alarm. By taking pin 1 low momentarily - they simulate the opening of a door. If you dont want the alarm to trip every time you turn on the ignition - simply leave out C3 & R4. 

Because the voltage on C3 may be reversed - the capacitor needs to be non-polarized. But connecting two regular 22uF capacitors back to back as shown - will work just as well. Because non-polarized capacitors are not widely available - the prototype was built using two polarized capacitors.

To reset the circuit you must - EITHER turn off the ignition - OR close all of the doors - before you press the reset button. While BOTH the ignition is on - AND a door remains open - the circuit will NOT reset.

The reset button carries virtually no current - so any small normally-open switch will do. Eric Vandel from Canada suggests using a reed-switch hidden behind (say) the dash - and operated by a magnet. I think this is an excellent idea. As Eric said in his email: - "... that should keep any thief guessing for a while."

Veroboard Layout

 

How you prevent the engine from starting is up to you. It should happen when Ry2 de-energizes. The contacts of Ry2 are too small to do the job themselves. So use them to switch the coil of a larger relay. Remember that the relay must be suitable for the current its required to carry. Choose one specifically designed for automobiles - it will be protected against the elements - and will give the best long-term reliability. You dont want it to let you down on a cold wet night - or worse still - in fast moving traffic!!! Remember also that you must fit a 1N4001 diode across YOUR relays coil - to prevent damage to the Cmos IC

YOUR relay should drop-out when Ry2 de-energizes. Wire YOUR relay so that when it drops-out the engine will not start. Because turning-off the ignition will cause both Ry2 and YOUR relay to de-energize - the standby current will be low - and the engine will be disabled while the vehicle is parked.

The circuit board must be protected from the elements. Dampness or condensation will cause malfunction. Fit a 1-amp in-line fuse AS CLOSE AS POSSIBLE to your power source. This is VERY IMPORTANT. The fuse is there to protect the wiring - not the components on the circuit board. Please note that I am UNABLE to help any further with either the choice of a suitable relay - or with advice on installation.

Both the Siren and the Buzzer will go on sounding until the alarm is reset. The circuit is designed to use an electronic Siren drawing up to about 500mA. Its not usually a good idea to use the vehicles own Horn because it can be easily located and disconnected. However, if you choose to use the Horn, remember that Ry1 is too small to carry the necessary current. Connect the coil of a suitably rated relay to the "Siren" output. This can then be used to sound the Horn.

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A Good Auto Sound System is a Requirement not a Luxury

How do you decide which auto sound system is best for you? This is a question that many consumers ask in the U. S. each and every day. The truth is that only you can decide what kind of sound you find enjoyable and what you are seeking in the sound system you will ultimately purchase. A good sound system will greatly improve how you feel about not only the vehicle you drive but also your disposition after your daily commute. It may seem like such a small thing, the changing of a sound system, but it does seem to have such a profound impact on how we start our days. Of course we all know that getting your day off to a good start sets the tone for the entire day and if that day is Monday it sets the tone for not only the day ahead but also the week to come.

Music affects almost every aspect of our lives. Most of us do not realize the impact that music has on our day-to-day lives and it is quite difficult because our world seems to be filled with it. It is much easier however, to explain the difference a good sound system makes. Its funny, I find myself in a hurry to get out of stores that have lousy sound systems and speakers that dribble out little more than static while I can shop for hours in a store that has tasteful music playing in the background over a good sound system. I prefer the volume lower and the music playing in the background rather than being the center of my attention.

Most of us find that soft music playing in the background is rather unobtrusive and allows us to get along with our thoughts and the mission at hand while loud music blaring over antiquated speakers does a great deal to disrupt our thought processes which will only serve to send us along to the next errand on our list. If youll notice it seems that clerks in the stores where the loud music blares along are often not as even tempered as those in stores that play music at respectful volumes and have very well kept sound systems. I think I would be cranky too after listening to music in a manner that music wasnt meant to be heard.

Im not a music snob by any means; I simply enjoy listening to music for the sake of actually hearing the music. Loud music is good sometimes but not when I have other things on my mind. I prefer that music remain in the background when Im running about taking care of errands, even in the car. The hallmark of a good auto sound system is that it sounds good even at low volumes. This means you can enjoy music in the background, hum along, or simply ignore the music in favor of the action taking place on the road.

The point Im trying to make is that even though you may not realize the impact that a good auto sound system has on music immediately, you will definitely feel the difference it makes over time. The better the sound system, the better the sound and music is after all, sound.

If you are a true lover of music and spend a great deal of your week or even any given day in your vehicle, doesnt it make sense to invest heavily in your auto sound system? I know for me that particular decision is a no brainer. I love music and it is an important part of not only my life but also the lives of my children. As a result we spend a lot of time listening to the radio in our SUV and singing along. Even when we arent listening to music, I enjoy listening talk radio and the news on NPR. These things are an important part of my day and I really enjoy all that each and every one adds to my life. Because of that, I find my investment in a good auto sound system to be a requirement rather than a luxury.

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The Importance of a Good Auto Sound System

If you spend a good deal of time in you car, and yes, the morning commute to work and the evening commute home each and every day definitely counts, you are probably more than slightly aware of the benefits of having a good auto sound system. Your sound system is your companion in your travels most of the time. Even those who have children often spend a great deal of time driving alone.

For those long and sometimes lonely miles your auto sound system is the voice of reason, the energetic beat, and the information that keeps you up on current events, weather forecasts, and what is going on in the world of the rich and famous. Even if you arent all that into music there is the wide and wonderful world of talk radio that keeps many of us informed and inflamed about issues that are important to us and causes which we feel passionately about.

The proper auto sound system affects the way we hear everything that comes through our radios. It doesnt really matter if you have the latest and greatest of subscription programs, XML programming, or even digital radio if your sound system is poor the quality of your programming will never reach your ears. Your sound system is the difference in standard sounds coming through your speakers and excellence making its way to your ears.

Contrary to popular belief however, you do not have to have the loudest sound system in order to have the best sound system. The truth of the matter is that once the music is so loud it ceases to sound like music and comes across to those inside and outside of your automobile more as noise than the wonderful music it may be in other circumstances. While there are many who enjoy the throbbing and jumping sounds that come from over emphasized bass, there is something to be said for an auto sound system that is well rounded and balanced. A good sound system will make all aspects of the music sound better and not just a certain few.

The important thing about sound systems arent the price that they command, the bass that they flaunt, or even the most minute details of the making and manufacturing of the sound system. The true beauty of a sound system lies in the fact that it should be music to your ears. You and you alone can choose the sound system that you like best as every person has different things they will listen for and enjoy in not only their music but also their sound systems. I love many different types of music and as a result will tend to listen to several different music genres as well as a stint of talk radio on several different systems and elect the one that sounds the best on the most of the music platforms and genres I prefer. I recommend a course of action similar to this to all who are interested in purchasing an auto sound system for their vehicle.

One thing that often gets overlooked is how much time we really spend in our vehicles in the course of a week. Most people pay very little time, money, or attention the particular stereos we put into our vehicles when in reality we spend nearly as much time each week listening to our auto sound systems as we do watching the televisions in our home. Music is all around us and it deeply affects and enhances our joys, our sorrows, even our romance. For those reasons, shouldnt we invest as much, if not more, time and energy in a great auto sound system as we do in a television for our homes?

By taking the time to get the perfect sound system for our vehicles when we first purchase our automobiles we will enjoy the maximum benefit our sound systems can provide. By enjoying our sound system, more people are willing to hang on to their vehicles longer which actually saves a great deal of money in the long run while also increasing your overall enjoyment of your time spent commuting to and from work each and every day.

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Auto Power Off

We are surrounded by battery operated equipment of all kinds, and this array is growing still. Manufacturers and designers lean over backwards to make sure that their equipment draws a small current and can thus be operated by a battery. This has its flip side, too. because even if the equipment in question draws only a small current, when it is not switched off, the battery is flat after a few days or weeks. The circuit presented here can prevent this happening. It may be added to all kinds of equipment operating from a 9 V battery and switches this off automatically one minute after a preset time has elapsed. The peak switching current is 20 mA, which is more than enough for most applications.
Circuit diagram:

Automatic Power Off Circuit Diagram

The switch is formed by a p-n-p darlington, T1, which is actuated by push-button switch S1. The very high amplification of the darlington enables it to be kept on fairly long with the aid of a relatively small-value capacitor, C1 (= 100 µF). Resistor R3 limits the charging current of C1 to ensure a long life of S1. Resistors R1 and R2, in conjunction with C1, determine the switch-on time. When this time has elapsed, R1 ensures that T1 is switched off. Since the darlington can handle a UBE of –10 V, a polarity protection diode is not needed.

Author:H. Bonekamp - Copyright: Elektor ELectronics

www.extremecircuits.net

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Auto Electrical Symbols

Auto Wiring Diagram Advanced Symbols.  for more complete information you can visit the automotive wiring schematic symbols

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