Micro-Controllers In Medical Field.

Introduction :

The microcontroller can be simply defined as a microchip or microcomputer or integrated circuit that contains programmable input/output peripherals, processor, and memory. There are various types of microcontrollers among which microcontroller 8051 is used frequently.

The microcontroller 8051 consists of four input/output ports, each port consists of eight pins which are configured as inputs/outputs based on logic state. If logic zero (0) is applied to appropriate input/output port bits, then the microcontroller pin acts as an output pin and there will be zero voltage at that appropriate pin. Similarly, if logic one (1) is applied to appropriate input/output port bits, then the microcontroller pin acts as an input pin and there will be 5V voltage at that appropriate pin.

Microcontrollers are intended for embedded devices, in comparison to the micro-processors which are used in PCs or other all-purpose devices. Microcontrollers are employed in automatically managed inventions and appliances like- power tools, implantable medical devices, automobile engine control systems, , office

machines, remote controls appliances, toys and many more embedded systems.

By dipping the size and expenditure in comparison to a design that make use of a different micro-processor, I/O devices and memory, micro-controllers formulate it inexpensive to digitally control more & more appliances and operations. Mixed signal micro-controllers are general; putting together analog constituents and are required controlling non-digital electronic structures.

Applications :

Application of Microcontroller in Day to Day Life Devices:

• Light sensing & controlling devices

• Temperature sensing and controlling devices

• Fire detection & safety devices

• Industrial instrumentation devices

• Process control devices

• Industrial instrumentation devices

• Process control devices

Application of Microcontroller in Metering & Measurement Devices:

• Volt Meter

• Measuring revolving objects

• Current meter

• Hand-held metering systems

Applications of Microcontroller in Medical Fields :

The application of microcontroller 8051 in medical applications made revolutionary changes in the medical field. The patient health monitoring system with location details by GPS over GSM is an electronic projectbased on the application of microcontroller. This project is designed for tracking the patient’s location suchthat it enables the facility to reach patient location quickly incase of emergency. With this project, the patient’sbody temperature can be monitored wirelessly using GPS and a message can be sent to the concerned/authorized person using GSM.

If the temperature of the patient’s body increases beyond the pre-set temperature, then the temperature sensor sends signal to the microcontroller. Thus, the microcontroller activates the GSM modem to send SMS to the concerned person based on details stored in EEPROM memory. Similarly, the location details of the patient are also sent using a GPS modem and the information is displayed on the LCD display.

Heart Beat Sensor :

A person’s heartbeat is the sound of the valves in his/her’s heart contracting or expanding as they force

blood from one region to another. The number of times the heart beats per minute (BPM), is the heart beat

rate and the beat of the heart that can be felt in any artery that lies close to the skin is the pulse.

Two Ways to Measure a Heartbeat :

Manual Way: Heart beat can be checked manually by checking one’s pulses at two locations- wrist (theradial pulse) and the neck (carotid pulse). The procedure is to place the two fingers (index and middle finger) on the wrist (or neck below the windpipe) and count the number of pulses for 30 seconds and then multiplying that number by 2 to get the heart beat rate. However pressure should be applied minimum and also fingers should be moved up and down till the pulse is felt.

Using a sensor: Heart Beat can be measured based on optical power variation as light is scattered or absorbed during its path through the blood as the heart beat changes.

Principle of Heartbeat Sensor :

The heartbeat sensor is based on the principle of photo phlethysmography. It measures the change in volume of blood through any organ of the body which causes a change in the light intensity through that organ (a vascular region).

In case of applications where heart pulse rate is to be monitored, the timing of the pulses is more important. The flow of blood volume is decided by the rate of heart pulses and since light is absorbed by blood, the signal pulses are equivalent to the heart beat pulses.

Working of a Heartbeat Sensor :Working of a Heartbeat Sensor :

The basic heartbeat sensor consists of a light emitting diode and a detector like a light detecting resistor or a photodiode. The heart beat pulses causes a variation in the flow of blood to different regions of the body. When a tissue is illuminated with the light source, i.e. light emitted by the led, it either reflects (a finger

tissue) or transmits the light (earlobe).
Some of the light is absorbed by the blood and the transmitted or the reflected light is received by the light detector. The amount of light absorbed depends on the blood volume in that tissue. The detector output is in form of electrical signal and is proportional to the heart beat rate.

This signal is actually a DC signal relating to the tissues and the blood volume and the AC component synchronous with the heart beat and caused by pulsatile changes in arterial blood volume is superimposed on the DC signal. Thus the major requirement is to isolate that AC component as it is of prime importance.

Heart Beat sensor :

To achieve the task of getting the AC signal, the output from the detector is first filtered using a 2 stage HP-

LP circuit and is then converted to digital pulses using a comparator circuit or using simple ADC. The digital pulses are given to a microcontroller for calculating the heat beat rate, given by the formula-

BPM(Beats per minute) = 60*f (Where f is the pulse frequency)

Conclusion :

Microcontroller based heartbeat monitor with LCD display IR led and LDR based heartbeat monitor with heart beats per minute from finger placing between the sensors. The sensor is made of simple photo resistor and LED. The pulses from the circuit are them amplified and converted into TTL logic pulses using comparator Operational Amplifier.