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If you have an electrical malfunction on your hands, there is only one way to determine its source with maximum efficiency, and that is to use a multimeter. Multimeters measure various electrical properties, including current, resistance and both AC and DC voltage. These instruments can be used by both professional electricians and the general public, and if you choose a Fluke multimeter, you can rest assured that you're using the very same tool that the pros rely on. Whether you invest in a brand new multimeter or find a discount Fluke multimeter online or at a bargain electronics retailer, you're going to need to know how to use it effectively - and safely. Here are some hints:

• Measuring Voltage: Begin by plugging the probes into the corresponding jacks on the multimeter; keep in mind that black is negative and the red should go only to the volt/ohm/temp jack. If you're measuring AC voltage, simply turn the dial to the "V" with a wavy line over it; to measure DC voltage, turn the dial to the "V" with a solid and a broken line over it. Finally, touch the probes to the outlet or wire you wish to monitor.
• Measuring Resistance: Start the same way as you would to measure voltage, but turn the dial to the "Ohm" sign. Then touch the probe tips together and read the resistance of the leads. You should be aware of the fact that the measured value of a resistor can differ from its rated value, usually by 0.1% to 0.2%.
• Measuring Current: Of the three uses for your Fluke multimeter, measuring current is the one that carries the greatest potential for danger. Before attempting this measurement, make sure to take all necessary safety precautions in order to avoid electrocution or serious damage to the meter. First, never attempt to make a measurement if the open-circuit potential to earth is greater than 1000 volts. Always check the fuses on your meter before beginning your measurement, and take care to use the proper terminals, function and range. Finally, never place the probes parallel to any circuit or component. Once these safety measures have been carried out, you're ready to begin! Turn off the power to the circuit and discharge high voltage capacitors. Then, insert the black lead into the COM terminal for currents between 6 mA and 400 mA, or insert the red lead into the A terminal for currents above 400 mA.

Follow these instructions and you can look forward to many years of safe and accurate readings from your Fluke digital multimeter.

Realizing computerized incubator with the aid of real-time technology

Realizing computerized incubator with the aid of real-time technology

1James Agajo, 2 A Sylvester Ezewele  3Awolo C. I.

Department of Electrical/Electronics

                   Federal Polytechnic, Auchi

Edo State ,Nigeria

Email:  agajojul@yahoo.com

Phone: +2348053312732

Abstract:- Realizing computerized incubator with the aid of real-time technology  , describe the design and implementation of an intelligent temperature controller based on fuzzy logic technology, the problem of precision in temperature control and monitoring was analyzed., microcontroller was programmed with the aid of EPROM programmer in realizing its automation.

Keywords: EPROM, Fuzzy logic, Real-Time, Control, Interface, microcontroller.

 

 

1.0 INTRODUCTION

Computerized incubator is an apparatus in which environmental conditions, such as temperature and humidity, can be controlled, often used for growing bacterial cultures, hatching eggs artificially, or providing suitable conditions for a chemical or biological reaction with the aid of real-time integrated system. They are special warm enclosure for keeping fertilized eggs to ensure satisfactory development of embryos inside them into normal birds.

Incubation of fowl eggs usually lasts for 21 days. The stage, eggs incubation is the most delicate stage in poultry husbandry because the proper care of eggs at this stage of developments has a decisive influence on the number of birds to be hatched and health of the hatched birds.

 

Fundamental elements of incubation are: the provision of heat, humidity, ventilation and turning of the eggs. The efficient combination of these factors determines the level of biological and physiological development and mortality of the embryo.

1.1 Incubating Conditions

Poor results are most commonly produced with improper control of temperature and humidity. Improper control means that the temperature or humidity is too high or too low for a sufficient length of time that it interferes with the normal growth and development of the embryo. Poor results also occur from improper ventilation, egg turning and sanitation of the machines or eggs. Obtain the best hatch by keeping the temperature at 100 degrees F. throughout the entire incubation period when using a forced-air incubator. Minor fluctuations (less than ½ degree) above or below 100 degrees are tolerated, but do not let the temperatures vary more than a total of 1 degree. Prolonged periods of high or low temperatures will alter hatching success. High temperatures are especially serious. A forced-air incubator that is too warm tends to produce early hatches. One that runs consistently cooler tends to produce late hatches. In both cases the total chicks hatched will be reduced.

 

Maintain a still-air incubator at 102 degrees F. to compensate for the temperature layering within the incubator. Obtain the proper temperature reading by elevating the bulb of the thermometer to the same height as the top of the eggs when the eggs are laying horizontal. If the eggs are positioned in a vertical position, elevate the thermometer bulb to a point about ¼- to ½-inch below the top of the egg. The temperature is measured at the level where the embryos develop (at the top of the egg). Do not allow the thermometer's bulb to touch the eggs or incubator. Incorrect readings will result.

 

 

2.0  Components and Appliances Used For the Design and Their Characteristics

 

1)      IC 8952 (Microcontroller)

2)      Active devices

1. Transistors (BC 337- NPN, BC 557-PNP)
2. Crystal oscillators
3. Diodes

3)      Passive Devices

1. Capacitor
2. Resistor

4)      The micro switch     

5) The Transformer

6)      The regulator 7805

7) The comparator (LM324)

The seven segment display

9) The relay

10) The Temperature Sensor (LM 35)

11) Electric bulb (100W)

12) Fan

These components are briefly discussed below:

 

2.1   8952 (Electrically Erasable programmable Read Only Memory)

IC 8951 is a microprocessor, which is a mini-computer –on-a-chip

The 8952 microcontroller is in practice a complete computer. It possesses the following characteristics:

 

1. 4KB of Read-Only Memory (ROM)
2. Four 8-bit I/O ports
3. 256 x 8 of Random Access Memory
4. A Programmable Serial UART  port
5. Six Interrupt Sources
6. External memory interface
7. Standard 40-pin package
8. Two 16-bit timer/ counters

Though the frequency of a crystal oscillator depends on how it is cut. That is, the frequency is determined by the manufacturers, but a careful analysis of the parameters that make up the frequency is as shown below.

Assuming the following parameters;

L = 0.33 H,     Cs = 3.0 x 10-3PF,        CP = 1.1 PF,    R = 10K

The series resonant frequency:

FS = 1/2p (1/LC) 1/2………………………………………..2.1

FS = 1/2p (1012           )1/2

­                      0.000099

     = 15995673.6 Hz

... The series resonant frequency, FS, is approximately 16MHz.

To calculate the percentage by which the parallel-resonant frequency exceeds the series- resonant frequency, we have;

Fp =     (1+CS)1/2          ……………………………………..2.2

FS                 CP

 

     = (1 + 0.00030)1/2

1.                         1.1       

    = (1 + 0.000273)1/2

   = 1.36

Therefore, FP exceeds FS by 33%

 

3.0          LM 35 TEMPERATURE SENSOR

           

The temperature sensor used in this project is the LM35. The LM35 measures temperature and gives an output voltage that is proportional to the Celsius temperature.

The LM35 has a low output impedance, linear output and precise inherent calibration that make interfacing to readout or control circuit especially easy.

The supply voltage (Vcc) is usually held at 5V. It draws only 60mA from its supply and hence possess a low self-heating capability. The sensor self-heating causes less than 0.1oC temperature rise in still air.

In the circuit, the ­Vout pin is connected to the Vin(+) pin of the ADC0804 while the Vcc is connected to a 5V supply and the GND pin grounded.

 

The sensor has a sensitivity of 10mV/oC. The conversion factor is 100oC/V.

The general equation used to convert output voltage to temperature is:

Temperature(oC) = Vout  C 100oC/V.

So if Vout  = 0.5V, then temperature = 0.5 x 100 = 50oC

Again, if the temperature controller is set to maintain the temperature below 30oC, then the maximum output voltage that will trip the relay is

Vout = 30oC/100 = 0.3V

The LM35 in measures temperature and gives an output voltage that is proportional to the Celsius temperature.

The scale factor is 0.0IV/OC. It does not require any external calibration or trimming and maintains an accuracy of +/- 0.8oc over a range of Ooc to + 100oc.

It also draws only 60 micro amps from its supply and possesses a low self-heating capability. The sensor self-heating causes less than OO/OC temperature rise in still on.

Typical voltage value of the LM35 is 5V. The sensor usually has a sensitivity of 10m V/oC.

The LM35 was actually built from the same resistance characteristics of devices such as the NTC Thermistor, which is a function of temperature. They usually have a low thermal are quickly reflected in a varying resistance as the mass.

For a thermistor, an expression for the resistance at any temperature is given by

(1)        R = RO* exp (Beta (1/T – 1/T o))

Where Beta is a constant force particular thermistor temperature TO and T are usually in degrees Kelvin. Typical values for R-O and T-O are 10.0k ohms and 300.0 degrees k.

Values of Beta are typically in the range of 3000  4000.

T – Kelvin = (T – f – 32.0) / 1.8 + 273

A general expression for temperature (T) as a function of resistance (R) is developed.

(2)  /T = 1/Beta X In (B) –1/Beta X In (Ro) + 1/T- 0

Substituting RO = 8870.0, TO = 300.9 and Beta = 3423.

(3)   1/T = 6.292 e-6 *In (R) + 6.6906e-4

The temperature in degree s I may than be calculated using the relation.

    I – f = (T – K – 273.0)* 1.8 + 32.6

            However, voltages at nodes, given x and y could also be calculated using the following relations.

(i)           V – x = 20.Oe3/(20.0e3 + R – Therm)* V – bridge

(ii)       V-y = 0.5 * V-bridge

(iii)       V-xy =V–x – V-y = (1/(1+R_therm/20.0e3) – 0.05)* V_bridge

(iv) V –xy/V-bridge = (1/(1+R-therm/20.0e3)-0.5)

4.0   ANALOG TO DIGITAL CONVERTER ADC

An ADC is an electronic device that converts continuous signals to discrete digital numbers. The reverse operation is done by a DAC. The digital output may be using different coding schemes such as binary and two’s compliment binary.

                

Most ADC’s are of a type known as linear which means that the range of input values that map to each output value has a linear relationship with the output value.

The ADC used is an IC, ADC 0804.

 

            The analogue voltage in figure 2a is applied to pin 6 and the result is available at P0.0 through 0.7 .Pin 1 and 2 (chip select and read) are connected to ground so that the chip is enabled. Pin 7 is also connected to ground.

 

The ADC 0804 includes an internal oscillator, which requires an internal capacitor and resistor  to operate.

            A 150Pf capacitor is connected from Pin A (Clock IN) to ground and the 10k ohm resistor from Pin 4 to Pin 19. (Clock R).

            If the input range of ADC is O-5V. Then Vref is set at 0.5, Vin maximum = 2.5V  Because ADC 0804 is 8bit, then

1. resolution =    255/5   = 0.02V                                                                 

 

       

This means the ADC will respond each 0.02V increasing. When conversion process is complete, P3 (interrupt) will go how and this signal is used to convert ADC again.

            Thus, an ADC with a resolution of 8bits can encode an analogue input to one in 256 different levels, since 28 = 256.

            Resolution can be expressed electrically and expressed in bits. The voltage resolution of an ADC is equal to its overall voltage measurement intervals as in the formula.

           

Q =    EFSR/2m-1

 

Q = resolution in volts

EFSR = full scale voltage range

M = resolution in bits

Q         =        5/2m – 1       =       5/  255

             Q = 0.02V

            RESOLUTION

The resolution of the converter indicated the number of discrete values it can produce over a range of analog values.

The values are usually stored electrically in binary form, so the resolution is usually expressed in bits.[1]

 

SAMPLING RATE

The analog signal is continuous in time and it is necessary to convert this to a flow of digital values. It is

Therefore required to define the rate at which the new digital values are sampled from the analog signal.

The rate of new values is called the sampling rate or sampling frequency of the converter.

     

ERRORS IN ADC

An ADC has several sources of error Quantization error and non-linearity in intrinsic to any A to D conversion.

Quantization error is due to the finite resolution of the ADC and is on unavailable imperfection in all types of ADC.

STEPS TAKEN IN ASSEMBLING THE PROGRAM

a)      Type the program in notepad.

b)      Save it as “tempControl.asm” in drive C:/

Ensure that drive C:/ has the 3 aplications (A51,OHS51 and L51) required to assembly the program

c)      Launch the “run” command from the start menu and type the commands

      a51.tempcontrol.asm

      l51.tempcontrol.obj

     ohs51.tempcontrol.obj

and then click OK,You cannot actually make the difference between the two steps, as the process is completely automated and indivisible. In case of syntax error in program code, program will not be compiled and HEX file will not be generated. Errors need to be corrected in the original .pbas file and then the source file may be compiled again. The best approach is to write and test small, logical parts of the program to make debugging easier.

The PM-51 Macro Assembler was used for this project. The term PM-51 belongs to an entire family of single-chip microcomputers, all of which have the same processor design. They use the same instruction set, but differ slightly in

Memory mapped special function registers and on-chip ROM and RAM. The assembler is a software tool- a program-designed to simply the task of writing computer programs. It performs the clerical task of translating symbolic code into executable object code. This object code may then be programmed into one of the PM-51 processor to which the 8051 belongs.

 

4.0   DEVELOPMENT OF THE PROGRAM

(i)                 Program Entry and Edit

            After the design is completed, the source code for each module is entered into file using a text editor. When errors are detected in the development process, text editor may be used to make correction in the source code.

(ii)        Assembling the Program:

                              The microcontroller cannot understand programs entered in assembly language. The process of converting assembly language into a suitable format is known as assembling the program. This is done using a program called assembler (ASM51) which translates the source code into object code.[1]

 

5.0 Tests and Result

The test was done by powering the incubator. When powered it displayed “set temperature”. The required temperature was entered using the increment button. Then the incubator attained the required temperature.

 

Also the work was tested and found to meet our specified requirement with efficiency of 70%.

No of fertile eggs used are 50

No of chicks hatched are 35

About the Author

James Agajo is into a P.H.D programme in digital signal processing related area, he has a Master Degree in Electronics and telecommunication Engineering and also possesses a Bachelor degree in Electronics and Computer Engineering from the Federal University of Technology Minna Nigeria. To his record, he has carried out researches in various areas as it concern telecommunication with particular emphasis on wirless communication network. His interest is in intelligent system development with a high flare for Engineering and Scientific research.He has Designed and implemented the most resent computer controlled robotic arm with a working grip mechanism 2006 which was aired on a national television , he has carried out work on using blue tooth technology to communicate with microcontroller. Has also worked on thumb print technology to develop high tech security systems with many more He is presently on secondment with UNESCO TVE as a supervisor and a resource person. James is presently registered with the Nigeria Society of Engineers.

Electronics question?

I'm looking for something that uses just, resistors, potentiometers, capacitors, and NPN transistors, to make it so that I can turn a potentiometer, and get a logic +5v high low output at different resistances of the potentiometer... I would also like it to be able to have a buffer attached, my teacher doesn't want his stamps to break or anything.

I'm not cheating in class or anything, I'm working on an open house project, and it has become very difficult to be able to figure this out... I'm trying to make a "special" analog to digital converter without using IC's, but the transistor that is suppose to flat out trigger, is still running between 0 and 5 volts.

Your question is not very clear.

Tell me exactly what is the digital interface to this discrete ADC you are trying to build.

If your only have one TTL input, then I suggest you make a VCO from your components and have the stamp try to measure the frequency (input voltage will be proportional to frequency).

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