Showing posts with label Automotive Projects. Show all posts
Showing posts with label Automotive Projects. Show all posts

Car Interior Lights Delay

Most cars do not have delayed interior lights. The circuit presented can put this right. It switches the interior lights of a car on and off gradually. This makes it a lot easier, for instance, to find the ignition keyhole when the lights have gone off after the car door has been closed. Since the circuit must be operated by the door switch, a slight intervention in the wiring of this switch is unavoidable.
When the car door is opened, the door switch closes the lights circuit to earth. When the door is closed (and the switch is open), transistor T1, whose base is linked to the switch, cuts off T2, so that the interior light remains off. When the switch closes (when the door is opened), the base of T1 is at earth level and the transistor is off.
Circuit diagram:
http://www.ecircuitslab.com/2011/06/car-interior-lights-delay.html
Capacitor C1 is charged fairly rapidly via R3 and D1, whereupon T2 comes on so that the interior light is switched on. When the door is closed again, T1 conducts and stops the charging of C1. However, the capacitor is discharged fairly slowly via R5, so that T2 is not turned off immediately.
This ensures that the interior light remains on for a little while and then goes out slowly. The time delays may be varied quite substantially by altering the values of R3, R5, and C1. Circuit IC2 may be one of many types of n-channel power MOSFET, but it should be able to handle drain-source voltages greater than 50 V. In the proto-type, a BUZ74 is used which can handle D-S voltages of up to 500 V.
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Car Boot Lamp Warning (ICM7556)

On many cars, the boot light will not go out until the lid is properly closed. It is all too easy when unloading the car, to leave the lid ajar. If you are unlucky and the car remains unused for some time, the next time you try to start it, the lamp will have drained the battery and you will no doubt utter a few appropriate words. The circuit described here will give a warning of just such a situation. 

A mercury tilt switch is mounted in the boot so that as the lid is closed, its contacts close before the lid is completely shut. The supply for the circuit comes from the switched 12 V to the boot lamp and through the mercury switch. When the lid is properly closed, the boot lamp will go out and the supply to the circuit will go to zero. If however the lid is left ajar, the lamp will be on and the mercury switch will close the circuit. 

Car Boot Lamp Warning (ICM7556) Circuit Diagram

Automotive Circuit Projects

After 5 seconds, the alarm will start to sound, and unless the lid is shut, it will continue for 1 minute to remind you to close the boot properly. The 1-minute operating period will ensure that the alarm does not sound continuously if you are, for example, transporting bulky items and the boot will not fully close. The circuit consists of a dual CMOS timer type 7556 (the bipolar 556 version is unsuitable for this application).

When power is applied to the circuit (i.e. the boot lid is ajar) tantalum capacitors C1 and C2 will ensure that the outputs of the timers are high. After approximately 5 seconds, when the voltage across C2 rises to 2/3 of the supply voltage, timer IC1b will be triggered and its output will go low thereby causing the alarm to sound.

Meanwhile the voltage across C1 is rising much more slowly and after approximately 1 minute, it will have reached 2/3 of the supply voltage. IC1a will now trigger and this will reset IC1b. The alarm will be turned off. IC1a will remain in this state until the boot lid is either closed or opened wider at which point C1 and C2 will be discharged through R6 and the circuit will be ready to start again. 

To calculate the period of the timers use the formula: t = 1.1RC Please note that the capacitor type used in the circuit should be tantalum or electrolytic with a solid electrolyte. The buzzer must be a type suitable for use at D.C. (i.e. one with a built in driver). 


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Lights On!

This circuit ensures that you will never again forget to switch on the lights of your car. As soon as the engine is running, the dipped beams and the sidelights are automatically switched on. The circuit also causes the dipped beams to be extinguished as soon as the main beams are switched on. As you can see from the schematic diagram, no special components are needed.

When the engine is running, the alternator will generate a voltage of more than 14 V. Diode D1 reduces this voltage by 5.6 V and passes it to the base of T1 via R1. Due to the resulting current, T1 conducts. The amplified current flows via R3, the base of T3 and D3 to ground. This causes T3 to also conduct and energize relay Re1.

Lights On! Circuit Diagram
Electronic Lights Circuit Diagram

If the driver now switches on the main beams, a current flows through D2 and R2 into the base of T2, causing this transistor to conduct. As a result, the voltage on the base of T3 drops, causing T3 to cut off and the relay to drop out.

 When the main beams are switched off, the previous situation is restored, and the relay again engages. The dipped beams and the sidelights are switched by the contacts of relay Re1. Diodes D5 and D6 ensure that the sidelights are illuminated if either the dimmed beams or the main beams are switched on. In practice, this means that the sidelights will be on whenever the engine is running, regardless of whether the main beams are switched on.

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A Simple Fog Lamp Switch

n most countries it is now mandatory or at least recommended to have a rear fog light on a trailer with the additional requirement that, when the trailer is coupled to the car, the rear fog light of the towing car has to be off. The circuit shown here is eminently suitable for this application. The circuit is placed near the rear fog light of the car. The 12-V connection to the lamp has to be interrupted and is instead connected to relay contacts 30 and 87A (K1, K3). When the rear fog light is turned on it will continue to operate normally.

Circuit diagram:

Fog Lamp Switch Circuit Diagram

If a trailer with fog light is now connected to the trailer connector (7- or 13-way, K2), a current will flow through L1. L1 is a coil with about 8 turns, wound around reed contact S1. S1 will close because of the current through L1, which in turn energizes relay Re1 and the rear fog light of the car is switched off. The fog light of the trailer is on, obviously. The size of L1 depends on reed contact S1. The fog lamp is 21 W, so at 12 V there is a current of 1.75 A. L1 is sized for a current between 1.0 and 1.5 A, so that it is certain that the contact closes. The wire size has to be about 0.8 mm. The relay Re1 is an automotive relay that is capable of switching the lamp current. The voltage drop across L1 is negligible.
Author : J. Geene Copyright :Elektor Electronics 2008

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Car Fan Speed Controller Using Timer 555

Using this circuit you can control the speed of 12V DC fans used in cars. The circuit is built around timer 555, which is wired as an astable multivibrator. The output of the multivibrator is fed to IRF 540 MOSFET. The fan is connected between the positive terminal of the battery and drain (D) of MOSFET T1. Capacitor C1 is connected in parallel to the fan to stabilise its speed. Free-wheeling diode D1 protects the motor from back emf. A fuse is included for protection.

Fig. 1: Car Fan Speed Controller Circuit Diagram

Automotive Circuit Diagram

Potmeter VR1 is used to change the duty cycle of the multivibrator and hence the speed of the fan. If you feel that low/high level of the fan speed is not sufficient, increase/decrease the value of C2 (0.47 µF) to reduce/increase the speed of the fan.

 Fig. 2: Pin Configuration of IRF540

Circuit Diagram

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Fix the potmeter at the front side of the case, so that you can easily change the speed of the fan. Connect the battery to the fan using wires with suitable current-carrying capacities. Use red wire for positive terminal and black wire for negative terminal.

Author :P.V. Vinod Thekkumuri - Copyright: EFY

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3 Volts Car Adapter Based on LT1074CT

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.


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Simple Servo Driver

When it comes to driving a servo you typically have to send a PWM signal to the servo input. The frequency of this signal is about 50 Hz and the duty cycle is variable. The duty cycle is usually between about 5 and 10%, corresponding with a pulse width of about 1 to 2 ms. The conversion of a resistance value into a PWM signal is fairly straightforward when a variable RC time constant circuit is used. Converting a voltage into a PWM signal is a bit more difficult, but it does offer some useful advantages.

Simple Servo Driver Circuit Diagram


When the position of a servo can be controlled via a voltage, it can be implemented via a potentiometer acting as a voltage divider. However, you could also use the output of a sensor such as a Hall sensor, an LDR or an NTC. That way you could easily create a feed-back loop that takes account of the position, light intensity or the temperature, and use this to control the servo. This can in turn be used to open or close a gas or water valve, for example. The circuit can therefore be said to be reasonably versatile.

There are special purpose PWM modulator ICs available, but it’s just as easy to use a quad op amp such as an LM324. In the circuit op amp C is configured to output a bias signal of half the supply voltage. Op amp D is set up as a square-wave oscillator, with its frequency set to about 50 Hz, which is the frequency required by the servo. The duty cycle is fixed and set to a value slightly higher than the maximum 10%.

This is followed by an integrator that changes the waveform of the pulse into a triangular form. Op amp B is configured as a comparator that compares this triangular wave with the DC voltage Uin. The output of the comparator is a PWM signal that is suitable to drive the servo directly. The frequency is about 50 Hz and the duty cycle can be varied from just under 5% to a good 10% when Uin varies from 0.5 to 4 V. The servo, an RS-2 in our prototype, reacts to this with an angular rotation of about 200 degrees. The transfer function in this case is therefore 200 / (4–0.5) = 57 degrees per volt.

Author: Gert Baars - Copyright: Elektor


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Lights Control for Model Cars

The author gave his partner a radio controlled (RC) model car as a gif t. She found it a lot of fun, but thought that adding realistic lights would be a definite improvement. So the author went back to his shed, plugged in his soldering iron, and set to work equipping the car with realistic indicators, headlights, tail lights and brake lights.

Lights Control for Model Cars Circuit Diagram


The basic idea was to tap into the signal from the radio control receiver and, with a bit of help from a microcontroller, simulate indicators using flashing yellow LEDs and brake lights using red LEDs. Further red LEDs are used for the tail lights, and white LEDs for the headlights. Connectors JP4 and JP5 (channel 0) are wired in parallel, as are JP6 and JP7 (channel 1), allowing the circuit to be inserted into the servo control cables for the steering and drive motor respectively. The ATtiny45 micro-controller takes power from the radio receiver via diode D1. T1 and T2 buffer the servo signals to protect IC1’s inputs from damage. 

IC1 analyses the PWM servo signals and gen-erates suitable outputs to switch the LEDs via the driver transistors. T3 drives the two left indicators (yellow), T4 the two right indica-tors, and T5 the brake LEDs (red). The red tail lights (JP2-8 and JP2-8) and the white head-lights (JP2-9 and JP2-10) are lit continuously. The brake lights are driven with a full 20 mA, so that they are noticeably brighter than the tail lights, which only receive 5 mA. If you wish to combine the functions of tail light and brake light, saving t wo red LEDs, sim-ply connect pin 10 of JP2 to pin 14 and pin 12 to pin 16. Then connect the two combined brake/tail LEDs either at JP2-5 and JP2-6 or at JP2-7 and JP2-8.

JP3 is provided to allow the use of a separate lighting supply. This can either be connected to an additional four-cell battery pack or to the main supply for the drive motor. The val-ues given for resistors R8 to R17 are suitable for use with a 4.8 V supply. JP2 can take the form of a 2x10 header.

As usual the sof t ware is available as a free download from the Elektor web pages accom-panying this article[1], and ready-programmed microcontrollers are also available. The microcontroller must be taught what servo signals correspond to left and right turns, and to full throttle and full braking. First connect the fin-ished circuit to the radio control electronics in the car, making sure everything is switched of f. Fit jumper JP1 to enable configuration mode, switch on the radio control transmit-ter, set all proportional controls to their cen-tre positions, and then switch on the receiver. The indicator LEDs should first flash on both sides. Then the car will indicate left for 3 s: during this time quickly turn the steering on the radio control transmitter fully to the left and the throt tle to full reverse (maximum braking).

Hold the controls in this position until the car starts to indicate right. Then set the controls to their opposite extremes and hold them there until both sides flash again. Now, if the car has an internal combustion engine (and so cannot go in reverse), keep the throttle control on full; if the car has an electric motor, set the throttle to full reverse. Hold this position while both sides are flashing. Configuration is now complete and JP1 can be removed. If you make a mistake during the configuration process, start again from the beginning.

Author: Manfred Stratmann - Copyright : Elektor


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Car & Motorcycle Battery Tester


Going camping nowadays involves taking lots of electronic equipment whether for day to day running or for fun and entertainment. Most of the time a charged lead-acid battery and a power inverter would be used to ensure a smoothly organised holiday where ideally the missus and the children cheerfully use their electric and electronic gear!

With rechargeable lead-acid batteries it’s invariably useful if not essential to determine whether the power source you’re hauling along on your travels is losing capacity and needs to be topped up.  The same circuit would also come in handy when going on a car or motorbike trip as it can check the status of a 12 V (car) or a 6 V (motorcycle) battery.

Car & Motorcycle Battery Tester Circuit Diagram

Car and Motorcycle Battery Tester

Although the circuit draws so little power that it will not notice-ably load the battery under test, it should not be left connected permanently. The circuit employs the familiar LM3914 (IC1) to display the voltage level. The LED readout creates a battery status readout:  when the top LED lights, the battery is fully charged. When the bottom LED lights, the battery needs imminent charging!

Switch S1 selects between 12 V and 6 V operation. A series diode, D1, protects the bargraph driver from reverse supply volt-age. A colour coded display with individual LEDs could be used instead of the common anode bargraph display for better indication of the state of the battery.
 
Author: Joseph Zamnit - Copyright: Elektor
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Voltage Limiter for Guitar Amplifiers

Guitar amplifiers using output devices such as the TDA7293 (100 W) or LM3886 (68 W) are surprisingly of ten damaged as a result of excessive supply voltage in the quiescent state. The transformers are of ten used so close to their specification that this problem can even be caused by a high mains input voltage. In most countries the domestic AC outlet voltage is permitted to rise as high 10 % above the nominal (published) value. Since replacing the transformer is not an attractive proposition, the author developed a relatively simple electronic solution to the overvoltage problem: a voltage limiter for the symmetric supply to the amplifier.
The circuit is based on the classical voltage regulator arrangement of a Zener diode connected to the base of a pass transistor. However, in this version we replace the conventional bipolar transistor with a power MOSFET.The circuit is symmetrical with respect to the negative and positive supplies, and so we shall only describe the positive half.
Voltage Limiter for Guitar Amplifiers Circuit Diagram
Voltage-Limiter-for-Guitar-Amplifiers-Circuit diagram
The input voltage (at most 50 V) supplies the chain of Zener diodes D1, D2 and D3 via resistor R3. The resistor limits the current through the Zener diodes to about 5 mA. The series connection of Zener diodes has the advantage that their dissipation is divided among them, as well as giving more options for the total voltage drop by judicious selection of individual components. The sum of the diode voltages (39 V with the values given) must be greater than the desired limiting out-put voltage by the gate-source voltage of the MOSFET. C1 smooths the voltage across the Zener diode chain. The circuit therefore not only limits the voltage, but also reduces the ripple (hum component) on the supply. The gate of the HEXFET is driven via R1. In con-junction with C4, this prevents the FET from oscillating.
Without any load the output voltage is rather higher than expected. With a small load, such as that presented by the output stage in its quiescent state, it falls to the desired value. The circuit then does not provide regulation of the output voltage, but rather a stabilisation function.The operation of the negative half of the circuit is identical to that of the positive half apart from the polarity of the voltages, and hence a P-channel MOSFE T must be used there.
It is worth noting that there is a relatively large degree of variation (up to a few volts) in the gate-source voltage of the HE XFETs used. This can be compensated for by selecting the Zener diodes in the chain and the cur-rent through them, but for most applications the exact voltage at which limiting begins to occur will not be critical.
The HEXFETs must be provided with adequate cooling. If possible, they can be attached to the heatsink already present in the amplifier; other wise, a separate heatsink will be required. A thermal rating of 2.5 K/W will be suitable.
Author :Alfred Rosenkränze - Copyright: Elektor
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Electronic Car Horn

An LM556 dual oscillator/timer, U1, configured as a two-tone oscillator drives U2, a dual 4-watt amplifier. One of the oscillators, pins 1 to 6, contained in U1 produces the upper frequency signal of about 200 Hz, while the second oscillator, pins 8 to 13, provides the lower frequency signal of about 140Hz.

Electronic Car Horn Circuit Diagram


Increase or decrease the frequencies by changing the values of C2 and C3. U1's outputs, pins 9 and 5, are connected to separate potentiometers to provide control over volume and balance. Each half of U2 produces 4W of audio that is delivered to two 8 ohms loudspeakers via capacitors C7 and C8.
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Automatic Wiper Control

A continuously working wiper is a big problem when it is raining slightly.The wiper control given here makes the wiper to sweep at rates from 1S to 10 S.

The circuit is build around an astable multivibrator using NE 555.Here the output at pin 3 remains high for a time period set by R2 ,and low for a time period set by R3.The low output pulse drives the transistor pair to drive the wiper motor to make one sweeping cycle and waits for next low pulse to arrive for next sweep.The high going pulse at pin 3 determines how many time should wiper should sweep in a given period of time.

Automatic Wiper Control Circuit Diagram:

Automatic-Wiper-Control-Circuit-Diagram

Notes:

  • Connect the circuit to 12V line from Vehicle and connect the wiper motor and wiper switch as shown in figure.
  • For setting the device first find out how much time it is required for the wiper to complete one sweep cycle.Now adjust
  • R3 such that wiper makes correct one sweep cycle.Fix R2 some where on the dash board.And now the system is ready to use.
  • You can adjust the sweep rate of the wiper using R2 according to the intensity of rain.

Source : Circuits today

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Low Cost Garage Stop Light

A novel use of solar cells makes positioning your car in the garage rather easier than old tyres, a mirror, or a chalk mark.The six solar cells in figure 1 serve as power supply and as proximity sensor. They are commercially available at relative low cost. The voltage developed across potentiometer Pi is mainly dependent on the intensity of the light falling onto the cells. The circuit is only actuated when the main beam of one of the car's headlights shines direct onto the cells from a distance of about 200 mm (8 inches). The distance can be varied somewhat with P,
Low Cost Garage Stop Light Circuit Diagram :
Low Cost Garage Stop Light-Circuit Diagram
Under those conditions, the voltage developed across C1 is about 3 V, which is sufficient to trigger relaxation oscillator Ni. The BC547B is then switched on via buffer N2 so that D3 begins to lfash. Diodes Di and D2 provide an additional in-crease in the threshold of the circuit. The total voltage drop of 1.2 V across them ensures that the potential at pin I of the 4093 is always 1.2 V below the voltage developed by the solar cells. As the trip level of Ni lies at about 50 per cent of the supply voltage, the oscillator will only start when the supply voltage is higher than 2.4 V.
The circuit, including the solar cells, is best constructed on a small veroboard as shown in figure 3, and then fitted in a translucent or transparent manmade fibre case. The case is fitted onto the garage wall in a position where one of the car's headlights shines direct onto it. The LED is fitted onto the same wall, but a little higher so that it is in easy view of the driver of the car. When you drive into the garage, you must, of course, remember to switch on the main beam of your headlights!
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Car Alarm Sound Booster

For car alarms, emphasis should be put on hearing the audible alert and identifying it as belonging to your ‘wheels’. Unfortunately, modern car alarm systems seem to have more or less the same alarm sound especially if they are from the same brand. Also, to comply with legal noise restrictions, the alarm sound is not always loud enough to be heard if the car is parked down the road.

The circuit shown here is designed to help boost the alarm sound by also activating the car’s horn(s) when the alarm goes off.Internally the car alarm system often provides a signal that activates the (optional) engine immobilizer and/or volume (ultrasound) sensors. This signal usually goes Low upon system triggering and high again when the alarm system is deactivated.

Car Alarm Sound Booster Circuit Diagram :

Car Alarm Sound Booster-Circuit Diagram

The alarm activation signal is fed to the circuit through D1. When in idle state, T1’s gate is High and consequently the FET conducts, keeping power FET T2 firmly switched of f. When the system gets an active low signal, T1 switches of f allowing timing capacitor C2 to charge via R2. About 15 seconds later, when the voltage across C2 is high enough, T2 starts to conduct and relay RE1 is energized. This, in turn, provides the required path for the ‘lights flashing’ signal to energize RE2 and feed battery power to the car’s horn(s).

When the alarm system is turned off the activation signal returns to High. T1 starts to con-duct and rapidly discharges C2 via R3. T2 is then cut off and RE1 is de-energized. Diode D2 suppresses back EMF from RE1.The circuit draws less than 2 mA when idling. When activated the circuit’s current consumption is virtually that of the RE1 coil.RE1 is any simple SPST or SPDT relay, capable of switching about 0.5 A (at 12 V). The coil rating is for 12 VDC and a current requirement as low as you can find. Fuse F1 should be a slow blow type and rated about twice RE1’s coil current.

The BS170 in position T2 can sink a continuous current of about 0.5 A. However, a value of 1.2 A pulsed is specified by Fairchild for their devices. To keep the FET’s d-s current due to C2 discharging within safe limits, R2 may be increased, C2 decreased and R3 increased, all proportionally. A factor of 2 will keep the FET out of harm’s way with maybe a slight change in the 15-second delay and the sensitivity of the circuit.C1 is used as a smoothing capacitor and F2 should be rated in accordance with the horn(s) maximum current draw.

Caution.The installation and use of this circuit may be subject to legal restrictions in your country, state or area.

Author : Hagay Ben-Elie - Copyright : Elektor

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Automotive Ignition Coil Buzz Box

 

Automotive Ignition Coil Buzz Box Circuit Diagram :

Ignition-Coil-Buzz-Box-Circuit diagram

 

This picture is a circuit for a buzz coil using a standard car battery to create. Dual timer IC 556 is used to set the frequency and the duty cycle of the coil current to be determined. One of the timer is used as an oscillator for generating the rectangular waveform 200 Hz to control (IRF740 MOSFET), while the second timer is stopped and the oscillator switching points are opened and closed (closed = a). The result is a steady stream of sparks of the ignition coil a distance of about 5 milliseconds, while the switching points are closed. Operation: Pin 8 and 12 the trigger inputs, and a timer which are driven by the points and an inverted signal of the clock output (pin 9) to produce.

When the pin 9 is grounded points high, and vice versa. The signal on pin 9 controls the reset line (pin 4) of the second timer and keeps the output at pin 5 is low, while pin 4 and pin 8 is low and 12 high (still open). The 15K and 47K resistors and capacitors are 0.33uF synchronization components that the frequency and duty cycle of the second clock, which is about 4 milliseconds to 2 milliseconds apart to secure positive and negative. During the time interval is positive, the doors are always high MOSFET causing the coil to the current height of about 4 amps.

This equates to approximately 80 milli joules of energy in the coil is released in the spark plug when the clock output (pin 5) moves on the ground, turn off the MOSFET. A zener diode 12 volts is placed on the node 10 and 27 ohms for the MOSFET gate input is above or below 12 volts -0.7 volts. A Zener diode 200 volts / 5 W used for the drain voltage of the MOSFET 200 and limit the useful life of the spark to expand. The circuit must operate reliably with a jumper, but the circuit operation with no load applied (the son of candle down, etc.) may cause a malfunction, because most of the energy absorbed by the Zener. You can also use a transient voltage suppressor (TVS) as 1.5KE300A 1.5KE200A or instead of the zener. This is probably a good hand, but difficult to obtain.

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Car's Brake Lights Monitor Circuit

The circuit described below monitors your car's brake lights, and indicates by a light emiting diode 12V whether they both function correctly. In that sense, it can save you money by preventing your being fined for driving with defective brake lights, and it also leads to increasing road safety.

Car's Brake Lights Monitor Circuit Diagram :

Car's Brake Lights Monitor-Circuit Diagram

The monitor depends inevitably on the voltage drop across the supply lines to the two lamps. For the circuit to work correctly, that drop needs to be greater  than 0.6 V. If this is not so, the drop must be in- creased by adding a 5 V diode in series with each  lamp. Transistor Ti and T2 in figure 1 form a  Schmitt trigger, which reacts to the voltage drop  across the supply lines to the two brake lights. This  reaction manifests itself in Di lighting via T3. If  one of the brake lights is faulty, the switch-on cur- rent drawn by the other lamp will cause Di to light  briefly when the brake pedal is pressed. If both  brake lights are defective, Di will not light at all. All three possible states of the brake lights are thus indicated. sitivity of the circuit, can be adjusted within narrow limits with Pi. The preset is best adjusted with one lamp out of action in a manner which makes Di light briefly as described above.

If you find it disturbing that Di lights every time you brake, the operation can be reversed by replacing the BC557B in the T3 position by a BC547B  (n-p-n). The collector of T3 is then connected to the  positive supply line, and the emitter to R6. On the  printed circuit board this means that the flat edge  of T3 must be turned the other way. A second base  connection has also been provided on the PCB.

Note, however, that this configuration no longer makes it possible to ascertain whether one or both brake lights are faulty, i.e., when the LED lights, one or both lamps need replacing.

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Simple Car-Reversing Horn with Flasher

Here is a simple circuit that starts playing the car horn whenever your car is in reverse gear. The circuit (refer Fig. 1) employs dual timer NE556 to generate the sound. One of the timers is wired as an astable multivibrator to generate the tone and the other is wired as a monostable multivibrator.

Circuit diagram :

 Simple Car-Reversing Horn with Flasher- Circuit Daigram

Fig. 1: Car reverse horn Circuit Diagram

Working of the circuit is simple. When the car is in reverse gear, reverse-gear switch S1 of the car gets shorted and the monostable timer triggers to give a high output. As a result, the junction of diodes D1 and D2 goes high for a few seconds depending on the time period developed through resistor R4 and capacitor C4. At this point, the astable multivibrator is enabled to start oscillating. The output of the astable multivibrator is fed to the speaker through capacitor C6. The speaker, in turn, produces sound until the output of the monostable is high.

When the junction of diodes D1 and D2 is low, the astable multivibrator is disabled to stop oscillating. The output of the astable multivibrator is fed to the speaker through capacitor C6. The speaker, in turn, does not produce sound.

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Connect the circuit to the car reverse switch through two wires such that S1 shorts when the car gear is reversed and is open otherwise. To power the circuit, use the car battery.

The flasher circuit (shown in Fig. 2) is built around timer NE555, which is wired as an astable multivibrator that outputs square wave at its pin 3. A 10W auto bulb is used for flasher. The flashing rate of the bulb is decided by preset VR1.

Flasher-circuit diagram

Fig. 2: Flasher Circuit Diagram

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. The flasher bulb can be mounted at the car's rear side in a reflector or a narrow painted suitable enclosure.

EFY note. A higher-wattage bulb may reduce the intensity of the headlight. You can enclose both the car-reversing horn and flasher circuits together or separately in a cabinet in your car.

Author :

Ashok K. Doctor - Copyright : EFY

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Simple Garage Stop Light Circuit

A novel use of solar cells makes positioning your car in the garage rather easier than old tyres, a mirror, or a chalk mark. The six solar cells in figure 1 serve as power supply and as proximity sensor. They are commercially available at relative low cost. The voltage developed across potentiometer Pi is mainly dependent on the intensity of the light falling onto the cells. The circuit is only actuated when the main beam of one of the car's headlights shines direct onto the cells from a distance of about 200 mm (8 inches). The distance can be varied somewhat with P,

Simple Garage Stop Light Circuit Diagram :

Simple-Garage-Stop-Light-Circuit Diagram

 

Under those conditions, the voltage developed across C1 is about 3 V, which is sufficient to trigger relaxation oscillator Ni. The BC547B is then switched on via buffer N2 so that D3 begins to  lfash. Diodes Di and D2 provide an additional in- crease in the threshold of the circuit. The total voltage drop of 1.2 V across them ensures that the  potential at pin I of the 4093 is always 1.2 V below the voltage developed by the solar cells. As the trip  level of Ni lies at about 50 per cent of the supply  voltage, the oscillator will only start when the supply voltage is higher than 2.4 V.

The circuit, including the solar cells, is best constructed on a small veroboard as shown in figure 3, and then fitted in a translucent or transparent man- made fibre case. The case is fitted onto the garage wall in a position where one of the car's headlights shines direct onto it. The LED is fitted onto the same wall, but a little higher so that it is in easy view of the driver of the car. When you drive into the garage, you must, of course, remember to switch on the main beam of your headlights!

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Brake Lights Monitor

The circuit described below monitors your car's  brake lights, and indicates by a light emiting diode  whether they both function correctly. In that sense, it can save you money by preventing your being fined for driving with defective brake lights, and it also leads to increasing road safety.

Circuit diagram :

Brake Lights Monitor-Circuit Diagram

Brake Lights Monitor Circuit Diagram

The monitor depends inevitably on the voltage drop across the supply lines to the two lamps. For the circuit to work correctly, that drop needs to be greater than 0.6 V. If this is not so, the drop must be increased by adding a 5 V diode in series with each lamp. Transistor Ti and T2 in figure 1 form a  Schmitt trigger, which reacts to the voltage drop across the supply lines to the two brake lights. This reaction manifests itself in Di lighting via T3. If  one of the brake lights is faulty, the switch-on cur- rent drawn by the other lamp will cause Di to light  briefly when the brake pedal is pressed. If both  brake lights are defective, Di will not light at all.  All three possible states of the brake lights are thus  indicated.

The hysteresis of the trigger, and, therefore, the sensitivity of the circuit, can be adjusted within narrow limits with Pi. The preset is best adjusted with one lamp out of action in a manner which makes Di light briefly as described above.

If you find it disturbing that Di lights every time  you brake, the operation can be reversed by replacing the BC557B in the T3 position by a BC547B  (n-p-n). The collector of T3 is then connected to the positive supply line, and the emitter to R6. On the printed circuit board this means that the flat edge  of T3 must be turned the other way. A second base  connection has also been provided on the PCB.  Note, however, that this configuration no longer makes it possible to ascertain whether one or both brake lights are faulty, i.e., when the LED lights, one or both lamps need replacing.

The printed circuit board is not available ready  made. In figure 1, Si is the brake pedal switch, and Lai and La2 are the brake lights.

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Car Cigar Lighter to USB Power Socket Circuit

Nowadays, almost all computer systems have logic blocks for working with a USB port. A USB port, in practice, is capable of supplying more than 100 mA of continuous electric current at 5V to the peripherals which are hooked up with the bus. So a USB port could be utilized, without having any problems, for powering 5V DC operated tiny electronic devices.

Cigar-Plug-USB-Power-Socket Circuit diagram

Today, a lot of handheld gadgets (for example, portable reading lamps) utilise this resource of the USB port to recharge their built-in battery pack using the support of an internal circuitry. Typically 5V DC, 100mA electric current is needed to satisfy the input electrical power demand.

The above diagram shows the circuit of a versatile USB power socket that properly converts the 12V battery voltage into stable 5V. This circuit can make it possible to power / recharge any USB power-operated device, working with in-dash board cigar lighter socket of the car.

 

usb qwe

The DC supply presented from the cigar lighter socket is fed to an adjustable, three-pin regulator LM317L (IC1).

Usb Pin 

Capacitor C1 buffers any disorder in the input supply. Resistors R1 and R2 regulate the output of IC1 to constant 5V, that is accessible at the ‘A’ type female USB socket. Red LED1 signifies the output condition and zener diode ZD1 acts as a protector against excessive voltage.

Assemble the circuit on a general purpose PCB and enclose inside a slim plastic cabinet as well as the indicator and USB socket. Whilst wiring the USB outlet, make sure proper polarity of the supply. For interconnection between the cigar plug pin as well as the device, use a long coil cord as shown in second image.

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