circuit wiring: speed

Showing posts with label speed. Show all posts

Sunday, October 6, 2013

Speed Limit Alert

Wireless portable unit, Adaptable with most internal combustion engine vehicles

This circuit has been designed to alert the vehicle driver that he/she has reached the maximum fixed speed limit (i.e. in a motorway). It eliminates the necessity of looking at the tachometer and to be distracted from driving. There is a strict relation between engines RPM and vehicle speed, so this device controls RPM, starting to beep and flashing a LED once per second, when maximum fixed speed is reached. Its outstanding feature lies in the fact that no connection is required from circuit to engine.

Circuit operation:

IC1 forms a differential amplifier for the electromagnetic pulses generated by the engine sparking-plugs, picked-up by sensor coil L1. IC2A further amplifies the pulses and IC2B to IC2F inverters provide clean pulse squaring. The monostable multivibrator IC3A is used as a frequency discriminator, its pin 6 going firmly high when speed limit (settled by R11) is reached. IC3B, the transistors and associate components provide timings for the signaling part, formed by LED D5 and piezo sounder BZ1. D3 introduces a small amount of hysteresis.

Circuit diagram:

Speed-limit Alert Circuit Diagram

Parts:

R1,R2,R19_______1K 1/4W Resistors
R3-R6,R13,R17_100K 1/4W Resistors
R7,R15__________1M 1/4W Resistors
R8_____________50K 1/2W Trimmer Cermet
R9____________470R 1/4W Resistor
R10___________470K 1/4W Resistor
R11___________100K 1/2W Trimmer Cermet (see notes)
R12___________220K 1/4W Resistor (see notes)
R14,R16________68K 1/4W Resistors
R18____________22K 1/4W Resistor
R20___________150R 1/4W Resistor (see notes)
C1,C7_________100µF 25V Electrolytic Capacitors
C2,C3_________330nF 63V Polyester Capacitors
C4-C6___________4µ7 25V Electrolytic Capacitors
D1,D5______Red LEDs 3 or 5mm.
D2,D3________1N4148 75V 150mA Diodes
D4________BZX79C7V5 7.5V 500mW Zener Diode
IC1__________CA3140 or TL061 Op-amp IC
IC2____________4069 Hex Inverter IC
IC3____________4098 or 4528 Dual Monostable Multivibrator IC
Q1,Q2_________BC238 25V 100mA NPN Transistors
L1_____________10mH miniature Inductor (see notes)
BZ1___________Piezo sounder (incorporating 3KHz oscillator)
SW1____________SPST Slider Switch
B1_______________9V PP3 Battery (see notes) Clip for PP3 Battery

Notes:

D1 is necessary at set-up to monitor the sparking-plugs emission, thus allowing to find easily the best placement for the device on the dashboard or close to it. After the setting is done, D1 & R9 can be omitted or switched-off, with battery savings.
During the preceding operation R8 must be adjusted for better results. The best setting of this trimmer is usually obtained when its value lies between 10 and 20K.
You must do this first setting when the engine is on but the vehicle is stationary.
The final simplest setting can be made with the help of a second person. Drive the vehicle and reach the speed needed. The helper must adjust the trimmer R11 until the device operates the beeper and D5. Reducing vehicles speed the beep must stop.
L1 can be a 10mH small inductor usually sold in the form of a tiny rectangular plastic box. If you need an higher sensitivity you can build a special coil, winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Extract the coil from the former and tape it with insulating tape making thus a stand-alone coil.
Current drawing is about 10mA. If you intend to use the car 12V battery, you can connect the device to the lighter socket. In this case R20 must be 330R.
Depending on the engines cylinders number, R11 can be unable to set the device properly. In some cases you must use R11=200K and R12=100K or less.
If you need to set-up the device on the bench, a sine or square wave variable generator is required.
To calculate the frequency relation to RPM in a four strokes engine you can use the following formula: Hz= (Number of cylinders * RPM) / 120.
For a two strokes engine the formula is: Hz= (Number of cylinders * RPM) / 60.
Thus, for a car with a four strokes engine and four cylinders the resulting frequency @ 3000 RPM is 100Hz.
Temporarily disconnect C2 from IC1 pin 6. Connect the generator output across C2 and Ground. Set the generator frequency to e.g. 100Hz and trim R11 until you will hear the beeps and LED D5 will start flashing. Reducing the frequency to 99 or 98 Hz, beeping and flashing must stop.
Please note that this circuit is not suited to Diesel engines.

Source : www.redcircuits.com

Wednesday, March 20, 2013

A Constant Torque DC Motor Speed Controller Circuit Using IC556 Explained

this source from swagatam at http//homemadecircuitsandschematics.blogspot.com/2011/12/constant-torque-dc-motor-speed.html

Controlling or varying a DC motor speed may appear to be not so difficult and you may find plenty of circuits for it. However these circuits do not guarantee consistent torque levels at lower motor speeds, making the functioning quite inefficient. Moreover at very low speeds due to insufficient torque, the motor tends to stall. Another serious drawback is that, there’s no motor reversal feature included with these circuits. The proposed circuit is completely free from the above shortcomings and is able to generate and sustain high torque levels even at lowest possible speeds.

Circuit Description

Before we discuss the proposed circuit, we would want also to learn the simpler alternative which is not so efficient, yet may be considered reasonably good as long as the load over the motor is not high and as long as the speed is not reduced to minimum levels.

The figure shows how a single 555 IC can be employed for controlling DC motor speed, we won’t go into the details, the only notable drawback of this configuration is that the torque is directly proportional to the speed of the motor.

Coming back to our main design, here we have used two 555 ICs instead of one or rather a single IC 556 that contains two 555 ICs in one package.

Briefly the proposed DC motor controller includes the following interesting features:

Speed can be varied continuously right from zero to maximum, without stalling.

The torque is never affected by the speed levels and remains constant even at minimum speed levels.

The motor rotation can be flipped or reversed within a fraction of second.

The speed is variable in both the directions of the motor rotation.

The two 555 ICs are assigned with two separate functions. One sections is configures as an astable multivibrator generating 100 Hz square wave clocks which is fed to the preceding 555 section inside the package.

The above frequency is responsible for determining the frequency of the PWM.

The transistor BC 557 is used as a constant current source which keeps the adjoining capacitor at its collector arm charged.

This develops a saw-tooth voltage across the above capacitor, which is compared inside the 556 IC with the sample voltage applied externally over over the shown pin-out.

The sample voltage applies externally can be derived from a simple 0-12V variable voltage power supply circuit.

This varying voltage applied to the 556 IC is used to vary the PWM of the pulses at the output and which eventually is used for the speed regulation of the connected motor.

The switch S1 is used to instantly reverse the motor direction whenever required.

Parts List

R1, R2, R6 = 1K,

R3 = 150K,

R4, R5 = 150 Ohms,

R7, R8, R9, R10 = 470 Ohms,

C1 = 0.1uF,

C2, C3 = 0.01uF,

C4 = 1uF/25V

T1, T2 = TIP122,

T3, T4 = TIP127

T5 = BC557,

T6, T7 = BC547,

D1---D4 = 1N5408,

Z1 = 4V7 400mW

IC1 = 556,

S1 = SPDT toggle switch

The above circuit was inspired from the following circuit which was published long back in elecktor electronic India magazine.