• View

  • Download

Embed Size (px)


Indication of RPM using GSMcontactless Tachometer





REVOLUTION PER MINUTES (RPM) INDICATOR is a system in which we get the speed of rotation of rotating machine. In past, we connect instrument with rotating parts. So that, To improve accuracy of this instrument we are going to make it contactless. The RPM reading will be sent to operator using GSM modem.

1.2 DETAILED DESCRIPTION OF PROBLEMIn Agriculture & Industry, When Power supply varies frequently, RPM also varies. From RPM, we can know power supply status. Due to High and low power supply, We lost rotating equipment like electrical motor. To resolve this problem, we will make this instrument. The Infra-Red sensor is placed in front of shaft of motor. A silver slit is placed along the diameter of shaft of motor. The sensor transmits light on the shaft. Light is reflected when strikes with slit on shaft. Reflected signal is converted in pulses which is gives to the microcontroller. Based on computation done in microcontroller, we get the RPM of testing device. This detail is display on LCD16x2 and send to the operator through GSM module. From RPM , we can know status of power supply & if supply high or low then we cutoff supply to rotating instrument automatically by Microcontroller.




2.1 IntroductionDigital RPM indicator are particularly suitable for the precision measurement and monitoring of all time related quantities, which are able to be converted into a proportional frequency using the appropriate sensors. Time-related quantities include rotational and linear velocity, flow rate and related quantities. The instrument can be programmed to measure absolute values ratio, or proportional frequency. The proportional frequency is generally produced by a magnetic wheel mounted on the shaft, which is scanned by a radial mounted impulse sensor. For control applications, a high resolution pick-up can be coupled directly to the motor shaft. The digital tachometer implements the period measurement method, with the subsequent calculation of a reciprocal value. Two absolute values, with independent set-up parameters, or their ratio or proportional difference (selectable) can be measured. The measurement is carried out automatically and repetitively, or externally through a contact. In ratio and proportional difference modes, the values used in the calculation are acquired simultaneously. These values are taken at the same point in time, without a delay, whereby a higher accuracy can be attained. In contemporary implementations, the values are taken successively. The first prototypes were based on optical sensors since these are normally easy to find. The first prototype was a wire wrapped design using the 8052 based microcontroller driving 8 of seven segment LED display characters. The sensor was an optical reflector sensor much like the Fairchild semiconductor qrb1114. The advantage to these sensors types is that they are usually in stock and very cheap. The sensor contains both an infra-red LED and infra-red photo NPN transistor as a detector. Both the sensor and detector are contained in an angled plastic case with a focal point approximately 2 inches from the sensor.


2.2 Infra- Red Sensor

FIG 2.1Internal circuit for Infra-Red sensor

One problem with these sensors is that they produce a very small signal depending on the type of material used to reflect infra-red light from the led into the detector and the distance from the material. An operational amplifier circuit can be used to amplify this signal to a more usable level. The idea behind most digital counting tachometers is a micro-controller, used to count the Pulses of a sensor or any other electronic device. In the case of this tachometer, the counted pulses comes from infra-red sensor, which detects any reflective element that passed in front of it, and thus, gives an output pulse for each and every rotation of the shaft. Those pulses are fed to the microcontroller and counted. The main difference of tachometer and frequency meters is that the reading in pulses per minutes (to count revolutions per minutes) is needed but in the same time, one does not want to wait a whole minute before obtaining a correct reading. Thus additional processing to predict the number of revolutions per minute in less than a second. It's necessary to be able to deduce an RPM reading


in less than second, while constantly refining the reading's accuracy, a simple algorithm have been developed, where a counter and a timer are used. Counter and timers are part of the internal features of a micro-controller, (like the AT89C52 used for the first prototype) and they can be easily configured through programming. The counter is connected in such a way as to count pulses coming from the infra-red sensor, while the timer is used to precisely feed the counted value to the microcontroller every fifth of a second, and reset the counter to 0. The microcontroller can now take an average of the last 3 readings (saved in C1, C2 and C3) and calculate the average numbers of pulses per fifth second, later this value is multiplied by 5 to get the number of pulses per second. Later this value is multiplied by 60 to get the number of pulses per minute, which represents the measured RPM.

FIG 2.2 pulse calculation for RPM measurementThe only purpose of calculating an average reading is that it allows more stable reading to be obtained and prevent fluctuating of the display. The problem with this method is that one cannot measure rpm values less that 60 rpm with a single pulse. Multiple pulses are required to improve the tachometer's accuracy.





ELECTRICAL: 1. Power supply voltage : 5v DC 2. Supply current required : 2000mA maximum

ENVIRONMENTAL: 1. Temperature : 10c to 60c 2. Humidity : 40%

MECHANICAL: 1. Module size : 70040025 mm(Approx)


3.2 COMPONENT SPECIFICATIONMicro controller ATMEL89CS52 Operating voltage: Temperature range: Power Consumption: 5.0V t 12mA

IR Proximity Sensor

Supply Voltage Temperatures range: Sensing range

4.5 to 5.5VDC t

0 to 80cm

GSM module SIM900

Operating voltage Temperature range

10 to 12v t

LCD 16x2 Display

Operating voltage Temperature range Power Consumption

4.7 to 5.3 V t 0.35mA





MOTOR (12V)`





LCD 16x2

FIG 4.1 Block diagram of Digital RPM measurement over GSM


4.2 COMPONENT LIST&DESCRIPTION: Component List:1. 2. 3. 4. 5. 6. Microcontroller AT89C52 IR Proximity sensor 16x2 LCD (JHD162A) GSM Module (SIM900) Resistors Capacitors

7. 12V DC Motor (Testing Device) 8. Battery (9v) & Battery Connector


4.2.1 Microcontroller AT89C51 Features: Compatible with MCS-51 Products 8K Bytes of In-System Programmable (ISP) Flash Memory Endurance: 10,000 Write/Erase Cycles 4.0V to 5.5V Operating Range Fully Static Operation: 0 Hz to 33 MHz Three-level Program Memory Lock 256 x 8-bit Internal RAM 32 Programmable I/O Lines Three 16-bit Timer/Counters Eight Interrupt Sources Full Duplex UART Serial Channel Low-power Idle and Power-down Modes Interrupt Recovery from Power-down Mode Watchdog Timer Dual Data Pointer Power-off Flag Fast Programming Time Flexible ISP Programming (Byte and Page Mode)



FIG 4.2 Pin configuration & Block diagram of 8051 microcontrollerThe whole configuration is obviously thought of as to satisfy the needs of most programmers working on development of automation devices. One of its advantages is that nothing is missing and nothing is too much. In other words, it is created exactly in accordance to the average users taste and needs. Another advantage is RAM organization, the operation of Central Processor Unit (CPU) and ports which completely use all recourses and enable further upgrade. PINOUT DESCRIPTION (a) Pins 1-8 port 1 each of these pins can be configured as an input or an output. (b) Pin 9 (Rs)A logic one on this pin disables the microcontroller and clears the contents of most registers. In other words, the positive voltage on this pin resets the microcontroller. By applying logic zero to this pin, the program starts execution from the beginning. (c) Pin 10-17:port 3:Similar to port 1, each of these pins can serve as general input or output. Besides, all of them have alternative functions: (d) Pin 10 Rxd Serial asynchronous communication input or Serial synchronous communication output. (e) Pin 11 Txd Serial asynchronous communication output or Serial synchronous communication clock output. (f) Pin 12 Int 0 Interrupt 0 input.


(g) Pin 13 Int 1 Interrupt 1 input. (h) Pin 14 Counter 0 clock input. (i) Pin 15 Counter 1 clock input. (j) Pin 16 WR Write to external (additional) RAM. (k) Pin 17 RD Read from external RAM. (l) Pin 18,19 XT, X1Internal oscillator input and output. A quartz crystal which specifies operating frequency is usually connected to these pins. Instead of it, miniature ceramics resonators can also be used for frequency stability. Later versions of microcontrollers operate at a frequency of 0 Hz up to over 50 Hz. (m) Pin 20 Ground. (n) Pin 21-22 if there is no intention to use external memory then these port pins are configured as general inputs/outputs. In case external memory is used, the higher address byte, i.e. addresses A8-A15 will appear on this port. Even though memory with capacity of 64Kb is not used, which means that not all eight port bits are used for its addressing