BATTERY TESTER FOR 1.5 AND 9 V BASIC ELECTRONICS PROJECT

BATTERY TESTER FOR 1.5 AND 9 V PROJECT

This is a basic electronics project for a Battery Tested for 1.5 and 9 Volts batteries. Below is the schematic diagram.

Parts List:

R1 = 18K

R2 = 240 Ohm

R3 = 8.2K

R4 = 3K

R5 = 10 Ohm

M1 = Panel Meter (Anyone will work)

Design Considerations:You may have experiment with the values of R3 and R4 to get an accurate reading from the meter. Every meter is different, so a little bit of playing with the resistor values is required.Try using a variable resistor in place of R3 & R4 to get a value of resistance that works.

Try and enjoy this basic project.

LASER DIODES BASIC AND TUTORIALS

LASER DIODES BASIC INFORMATION
What Are Laser Diodes?

The laser diode is a further development upon the regular light-emitting diode, or LED. The term "laser" itself is actually an acronym, despite the fact it's often written in lower-case letters.

"Laser" stands for Light Amplification by Stimulated Emission of Radiation, and refers to another strange quantum process whereby characteristic light emitted by electrons transitioning from high-level to low-level energy states in a material stimulate other electrons in a substance to make similar "jumps," the result being a synchronized output of light from the material.


This synchronization extends to the actual phase of the emitted light, so that all light waves emitted from a "lasing" material are not just the same frequency (color), but also the same phase as each other, so that they reinforce one another and are able to travel in a very tightly-confined, nondispersing beam.

This is why laser light stays so remarkably focused over long distances: each and every light wave coming from the laser is in step with each other:

Incandescent lamps produce "white" (mixed-frequency, or mixed-color) light. Regular LEDs produce monochromatic light: same frequency (color), but different phases, resulting in similar beam dispersion.

 Laser LEDs produce coherent light : light that is both monochromatic (single-color) and monophasic (single phase), resulting in precise beam confinement.

Laser light finds wide application in the modern world: everything from surveying, where a straight and nondispersing light beam is very useful for precise sighting of measurement markers, to the reading and writing of optical disks, where only the narrowness of a focused laser beam is able to resolve the microscopic "pits" in the disk's surface comprising the binary 1's and 0's of digital information.

Some laser diodes require special high-power "pulsing" circuits to deliver large quantities of voltage and current in short bursts. Other laser diodes may be operated continuously at lower power.

In the latter case, laser action occurs only within a certain range of diode current, necessitating some form of current-regulator circuit. As laser diodes age, their power requirements may change (more current required for less output power), but it should be remembered that low-power laser diodes, like LEDs, are fairly long-lived devices, with typical service lives in the tens of thousands of hours.

DIODE RATINGS BASIC AND TUTORIALS

RATINGS OF DIODES BASIC INFORMATION
What Are The Ratings Of Diodes?

In addition to forward voltage drop (Vf ) and peak inverse voltage (PIV), there are many other ratings of diodes important to circuit design and component selection. Semiconductor manufacturers provide
detailed specifications on their products { diodes included { in publications known as datasheets.
Datasheets for a wide variety of semiconductor components may be found in reference books and on the internet. I personally prefer the internet as a source of component specifications because all the data obtained from manufacturer websites are up-to-date.

A typical diode datasheet will contain figures for the following parameters:

Maximum repetitive reverse voltage = VRRM, the maximum amount of voltage the diode can withstand in reverse-bias mode, in repeated pulses. Ideally, this figure would be infinite.

Maximum DC reverse voltage = VR or VDC, the maximum amount of voltage the diode can withstand in reverse-bias mode on a continual basis. Ideally, this figure would be infinite.

Maximum forward voltage = VF , usually specified at the diode's rated forward current. Ideally, this figure would be zero: the diode providing no opposition whatsoever to forward current. In reality, the forward voltage is described by the "diode equation."

Maximum (average) forward current = IF(AV ), the maximum average amount of current the
diode is able to conduct in forward bias mode. This is fundamentally a thermal limitation: how
much heat can the PN junction handle, given that dissipation power is equal to current (I) multiplied
by voltage (V or E) and forward voltage is dependent upon both current and junction temperature.
Ideally, this figure would be infinite.

Maximum (peak or surge) forward current = IFSM or if(surge), the maximum peak amount of current the diode is able to conduct in forward bias mode. Again, this rating is limited by the diode junction's thermal capacity, and is usually much higher than the average current rating due to thermal inertia (the fact that it takes a finite amount of time for the diode to reach maximum temperature for a given current). Ideally, this figure would be infinite.

Maximum total dissipation = PD, the amount of power (in watts) allowable for the diode to dissipate, given the dissipation (P=IE) of diode current multiplied by diode voltage drop, and also the dissipation (P=I2R) of diode current squared multiplied by bulk resistance. Fundamentally limited by the diode's thermal capacity (ability to tolerate high temperatures).

Operating junction temperature = TJ , the maximum allowable temperature for the diode's PN junction, usually given in degrees Celsius (oC). Heat is the "Achilles' heel" of semiconductor devices: they must be kept cool to function properly and give long service life.

Storage temperature range = TSTG, the range of allowable temperatures for storing a diode (un- powered). Sometimes given in conjunction with operating junction temperature (TJ ), because the maximum storage temperature and the maximum operating temperature ratings are often identical. If anything, though, maximum storage temperature rating will be greater than the maximum operating temperature rating.

Thermal resistance = R(£), the temperature difierence between junction and outside air (R(£)JA) or between junction and leads (R(£)JL) for a given power dissipation. Expressed in units of degrees Celsius per watt (oC/W).

Ideally, this figure would be zero, meaning that the diode package was a perfect thermal conductor and radiator, able to transfer all heat energy from the junction to the outside air (or to the leads) with no difierence in temperature across the thickness of the diode package.

A high thermal resistance means that the diode will build up excessive temperature at the junction (where it's critical) despite best efiorts at cooling the outside of the diode, and thus will limit its maximum power dissipation.

Maximum reverse current = IR, the amount of current through the diode in reverse-bias operation, with the maximum rated inverse voltage applied (VDC). Sometimes referred to as leakage current.

Ideally, this figure would be zero, as a perfect diode would block all current when reverse- biased. In reality, it is very small compared to the maximum forward current.

Typical junction capacitance = CJ , the typical amount of capacitance intrinsic to the junction, due to the depletion region acting as a dielectric separating the anode and cathode connections. This is usually a very small figure, measured in the range of picofarads (pF).

Reverse recovery time = trr, the amount of time it takes for a diode to "turn ofi" when the voltage across it alternates from forward-bias to reverse-bias polarity. Ideally, this figure would be zero: the diode halting conduction immediately upon polarity reversal.

For a typical rectifier diode, reverse recovery time is in the range of tens of microseconds; for a "fast switching" diode, it may only be a few nanoseconds.

Most of these parameters vary with temperature or other operating conditions, and so a single figure fails to fully describe any given rating. Therefore, manufacturers provide graphs of component ratings plotted against other variables (such as temperature), so that the circuit designer has a better idea of what the device is capable of.

MULTIMETER CHECK OF DIODES BASIC AND TUTORIALS

CHECKING DIODES USING METER BASIC INFORMATION
How To Check Diodes Using Multimeter Tutorials?

Being able to determine the polarity (cathode versus anode) and basic functionality of a diode is a very important skill for the electronics hobbyist or technician to have.

Since we know that a diode is essentially nothing more than a one-way valve for electricity, it makes sense we should be able to verify its one-way nature using a DC (battery-powered) ohmmeter.


Connected one way across the diode, the meter should show a very low resistance. Connected the other way across the diode, it should show a very high resistance ("OL" on some digital meter models):

Of course, in order to determine which end of the diode is the cathode and which is the anode, you must know with certainty which test lead of the meter is positive (+) and which is negative (-) when set to the "resistance" or "­" function.

With most digital multimeters I've seen, the red lead becomes positive and the black lead negative when set to measure resistance, in accordance with standard electronics color-code convention. However, this is not guaranteed for all meters.

Many analog multimeters, for example, actually make their black leads positive (+) and their red leads negative (-) when switched to the "resistance" function, because it is easier to manufacture it that way!

One problem with using an ohmmeter to check a diode is that the readings obtained only have qualitative value, not quantitative. In other words, an ohmmeter only tells you which way the diode conducts; the low-value resistance indication obtained while conducting is useless.

If an ohmmeter shows a value of "1.73 ohms" while forward-biasing a diode, that figure of 1.73 ­ doesn't represent any real-world quantity useful to us as technicians or circuit designers. It neither represents the forward voltage drop nor any "bulk" resistance in the semiconductor material of the diode itself, but rather is a figure dependent upon both quantities and will vary substantially with the particular ohmmeter used to take the reading.

For this reason, some digital multimeter manufacturers equip their meters with a special "diode check" function which displays the actual forward voltage drop of the diode in volts, rather than a "resistance" ¯gure in ohms. These meters work by forcing a small current through the diode and measuring the voltage dropped between the two test leads:

The forward voltage reading obtained with such a meter will typically be less than the "normal" drop of 0.7 volts for silicon and 0.3 volts for germanium, because the current provided by the meter is of trivial proportions. 

If a multimeter with diode-check function isn't available, or you would like to measure a diode's forward voltage drop at some non-trivial current, the following circuit may be constructed using nothing but a battery, resistor, and a normal voltmeter:

Connecting the diode backwards to this testing circuit will simply result in the voltmeter indi-

cating the full voltage of the battery.

If this circuit were designed so as to provide a constant or nearly constant current through the diode despite changes in forward voltage drop, it could be used as the basis of a temperature measurement instrument, the voltage measured across the diode being inversely proportional to diode junction temperature. 

Of course, diode current should be kept to a minimum to avoid self-heating (the diode dissipating substantial amounts of heat energy), which would interfere with temperature measurement.

Beware that some digital multimeters equipped with a "diode check" function may output a very low test voltage (less than 0.3 volts) when set to the regular "resistance" (­) function: too low to fully collapse the depletion region of a PN junction. 

The philosophy here is that the "diode check" function is to be used for testing semiconductor devices, and the "resistance" function for anything else. By using a very low test voltage to measure resistance, it is easier for a technician to measure the resistance of non-semiconductor components connected to semiconductor components, since the semiconductor component junctions will not become forward-biased with such low voltages.

Consider the example of a resistor and diode connected in parallel, soldered in place on a printed circuit board (PCB). Normally, one would have to unsolder the resistor from the circuit (disconnect it from all other components) before being able to measure its resistance, otherwise any parallel- connected components would affect the reading obtained. 

However, using a multimeter that outputs a very low test voltage to the probes in the "resistance" function mode, the diode's PN junction will not have enough voltage impressed across it to become forward-biased, and as such will pass negligible current. 

Consequently, the meter "sees" the diode as an open (no continuity), and only registers the resistor's resistance:

If such an ohmmeter were used to test a diode, it would indicate a very high resistance (many mega-ohms) even if connected to the diode in the "correct" (forward-biased) direction:

Reverse voltage strength of a diode is not as easily tested, because exceeding a normal diode's PIV usually results in destruction of the diode. There are special types of diodes, though, which are designed to "break down" in reverse-bias mode without damage (called Zener diodes), and they are best tested with the same type of voltage source / resistor / voltmeter circuit, provided that the voltage source is of high enough value to force the diode into its breakdown region.

ABSOLUTE dB SCALE BASICS AND TUTORIALS

ABSOLUTE dB SCALE BASIC INFORMATION
What Is The Absolute dB Scale?

It is also possible to use the decibel as a unit of absolute power, in addition to using it as an expression of power gain or loss. A common example of this is the use of decibels as a measurement of sound pressure intensity.

In cases like these, the measurement is made in reference to some standardized power level de¯ned as 0 dB. For measurements of sound pressure, 0 dB is loosely defined as the lower threshold of human hearing, objectively quanti¯ed as 1 picowatt of sound power per square meter of area.


A sound measuring 40 dB on the decibel sound scale would be 104 times greater than the threshold of hearing. A 100 dB sound would be 1010 (ten billion) times greater than the threshold of hearing.

Because the human ear is not equally sensitive to all frequencies of sound, variations of the decibel sound-power scale have been developed to represent physiologically equivalent sound intensities at different frequencies.

Some sound intensity instruments were equipped with filter networks to give disproportionate indications across the frequency scale, the intent of which to better represent the effects of sound on the human body.

Three ¯ltered scales became commonly known as the "A," "B," and "C" weighted scales. Decibel sound intensity indications measured through these respective filtering networks were given in units of dBA, dBB, and dBC.

Today, the "A-weighted scale" is most commonly used for expressing the equivalent physiological impact on the human body, and is especially useful for rating dangerously loud noise sources.

Another standard-referenced system of power measurement in the unit of decibels has been established for use in telecommunications systems. This is called the dBm scale. The reference point, 0 dBm, is de¯ned as 1 milliwatt of electrical power dissipated by a 600 ­ load.

According to this scale, 10 dBm is equal to 10 times the reference power, or 10 milliwatts; 20 dBm is equal to 100 times the reference power, or 100 milliwatts. Some AC voltmeters come equipped with a dBm range or scale (sometimes labeled "DB") intended for use in measuring AC signal power across a 600 ­ load.

0 dBm on this scale is, of course, elevated above zero because it represents something greater than 0 (actually, it represents 0.7746 volts across a 600 ­ load, voltage being equal to the square root of power times resistance; the square root of 0.001 multiplied by 600). When viewed on the face of an analog meter movement, this dBm scale appears compressed on the left side and expanded on the right in a manner not unlike a resistance scale, owing to its logarithmic nature.

An adaptation of the dBm scale for audio signal strength is used in studio recording and broadcast engineering for standardizing volume levels, and is called the VU scale. VU meters are frequently seen on electronic recording instruments to indicate whether or not the recorded signal exceeds the maximum signal level limit of the device, where signi¯cant distortion will occur.

This "volume indicator" scale is calibrated in according to the dBm scale, but does not directly indicate dBm for any signal other than steady sine-wave tones. The proper unit of measurement for a VU meter is volume units.

When relatively large signals are dealt with, and an absolute dB scale would be useful for representing signal level, specialized decibel scales are sometimes used with reference points greater than the 1mW used in dBm. Such is the case for the dBW scale, with a reference point of 0 dBW established at 1 watt. Another absolute measure of power called the dBk scale references 0 dBk at 1 kW, or 1000 watts.