Speed Limit Alarm Circuit

Labels: Alarm

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 engine's 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 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

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.

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 vehicle's 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 engine's 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

See Also: Instant Power Supply Circuit Diagram

100W Inverter Circuit

Labels: Inverter

Inverter changes direct current (DC) to alternating current (AC). This is inverter 100W circuit.

Circuit Diagram

Circuit Diagram Of 100W Inverter

IPS Circuit

Labels: IPS

Here is the circuit diagram of a simple IPS (Instant Power Supply). The circuit is simple low cost and can be even assembled on a veroboard.

IPS Circuit

Instant Power Supply Circuit Diagram

Backup depends on the ampere of your battery and how many machines (fans, lights etc) you are running. It also depends on Watt of IPS. A fan and three energy lights can be run by a 200W of IPS.
To get more backup time you have to increase your battery power. And if you want to run more than one fan or add other machine you also need to increase Watt of IPS. In order to maximize the watt of IPS you must increase the quantity of FET & Transformer value.

See Also: Speed Limit Alarm Circuit

Atoms and Their Structure

Labels: Intro

A basic understanding of the fundamental concept of current and voltage requires a degree of familiarity with the atom and its structure. The simplest of all atoms is the hydrogen atom, made up of two basic particles, the proton and the electron, in the relative positions shown in given screenshot.

Hydrogen atom

The nucleus of the hydrogen atom is the proton, a positively charged particle. The orbiting electron carries a negative charge that is equal in magnitude to the positive charge of the proton. In all other elements, the nucleus also contains neutrons, which are slightly heavier than protons and have no electrical charge. The helium atom, for example, has two neutrons in addition to two electrons and two protons, as shown in given picture.

Helium atom

In all neutral atoms the number of electrons is equal to the number of protons. The mass of the electron is 9.11x10^-28 g, and that of the proton and neutron is 1.672x10^-24 g. The mass of the proton (or neutron) is therefore approximately 1836 times that of the electron. The radii of the proton, neutron and electron are all of the order of magnitude of 2x10^-15 m

For the hydrogen atom, the radius of the smallest orbit followed by the electron is about 5x10¹¹ m. The radius of this orbit is approximately
25,000 times that of the radius of the electron, proton, or neutron. This is approximately equivalent to a sphere the size of a dime revolving about another sphere of the same size more than a quarter of a mile away.

Different atoms will have various numbers of electrons in the concentric shells about the nucleus. The first shell, which is closest to the nucleus, can contain only two electrons. If an atom should have three electrons, the third must go to the next shell. The second shell can contain a maximum of eight electrons; the third, 18; and the fourth, 32; as determined by the equation 2n², where n is the shell number. These shells are usually denoted by a number (n 1, 2, 3, . . .) or letter (n k, l, m, . . .).

Each shell is then broken down into subshells, where the first subshell can contain a maximum of two electrons; the second subshell, six electrons; the third, 10 electrons; and the fourth, 14; as shown in fig. given below.

Shells and subshells of the atomic structure

The subshells are usually denoted by the letters s, p, d, and f, in that order, outward from the nucleus. It has been determined by experimentation that unlike charges attract, and like charges repel. The force of attraction or repulsion between two charged bodies Q1 and Q2 can be determined by Coulomb’s law:

Eq: 2.1

Coulomb’s law

(newtons, N) where F is in newtons, k = a constant ϭ 9.0 x 10⁹ N⋅m² /C² , Q1 and Q2 are the charges in coulombs, and r is the distance in meters between the two charges. In particular, note the squared r term in the denominator, resulting in rapidly decreasing levels of F for increasing values of r.

In the atom, therefore, electrons will repel each other, and proton sand electrons will attract each other. Since the nucleus consists of many positive charges (protons), a strong attractive force exists for the electrons in orbits close to the nucleus [note the effects of a large charge Q and a small distance r
in Eq. (2.1)]. As the distance between the nucleus and the orbital electrons increases, the binding force diminishes until it reaches its lowest level at the outermost subshell (largest r). Due to the weaker binding forces, less energy must be expended to remove an electron from an outer subshell than from an inner subshell. Also, it is generally true that electrons are more readily removed from atoms having outer subshells that are incomplete and, in addition, possess fewelectrons. These properties of the atom that permit the removal of elec-trons under certain conditions are essential if motion of charge is to becreated. Without this motion, this text could venture no further—our basic quantities rely on it.

Copper is the most commonly used metal in the electrical/electronics industry. An examination of its atomic structure will help identify why it has such wide spread applications. The copper atom (Screenshot Below)has one more electron than needed to complete the ﬁrst three shells. This incomplete outermost subshell, possessing only one electron, and the distance between this electron and the nucleus reveal that the twenty-ninth electron is loosely bound to the copper atom. If this twenty-ninth electron gains sufﬁcient energy from the surrounding medium to leave its parent atom, it is called a free electron. In one cubic inch of copper at room temperature, there are approximately 1.4x10²⁴ free electrons. Other metals that exhibit the same properties as copper, but to a different degree, are silver, gold, aluminum, andtungsten. Additional discussion of conductors and their characteristics can be found in next article.

The copper atom