| My Goal |
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I'm designing a Holter Monitor to cardiac signals that store for 24 hours, the design must use 4 batteries AA as a power source while should methods to extend the life of the batteries.
The Holter Monitor includes 4GB memory SD and a Bluetooth module for transmisicion data to a mobile device that will serve to display the beats per minute (PPM) of the patient.
In the memory must store the impression Time and Date, together with PPM
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| Block Diagram |
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The following diagram shows the basic idea of the project.
As the project was progressed in its development, I had to make some corrections and modifications to the diagram, as a result have the following picture:
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| Hardware Implementation |
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First is implemented, communication with the SD memory [1] and communication with the DS1302 [2] clock circuit.
the power supply voltage symmetrical [3] of +1.5 and -1.5V , in order to operate as a power source for cardiac signal amplifiers.
This time the high quality amplifiers OPA316 [4] company Texas Instruments is used in the stage cardiac amplifier, which allow me a better behavior of the analog signal and a lower offset voltage.
As a last step the Bluetooth RN42 [5] module is configured and connect.
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Software Implementation (Still Beta) All application of Holter monitor, this check in Energia 17 |
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This image shows the form of heart wave, catch the oscilloscope.
For treatment of cardiac signal, the first capture each 14.6ms a number of 1024 samples, to capture 15 seconds of the cardiac signal.
Then the cardiac signal is derived to obtain a vector where we find it much easier to recognize what points maximums of cardiac function.
Eliminate the negative area "derived vector", so only work with positive values, an algorithm to count the number of peaks stored during a sampling period of 15 seconds is then implements, and for last this value is multiplied by 4 to obtain the pulse per minute.
Implementation of communication with the DS1302 Clock by energia.nu
The algorithm of counting pulses and display of heart beats per minute in the serial screen Energia.nu
Finally the transmission was implemented by bluetooth to the mobile deice and here the result. (During these tests, there was no patient connected to the computer so the measurement pulse is erratic, even I must devote more hours to count algorithm hehe
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| In the next part |
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I just hope to improve the algorithm and design of the heart amplifier, since I'm working with a bandwidth of 200Hz, many components are used, will simplify the design of amplifier and filter Analogs by an amplifier and a low pass filter to 16Hz.
I hope the circuit and greatly reduce the power consumption, thus increasing battery life. |
References |
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[1] TI Launchpad MSP432 Memory SD and Energia.nu [3] TIDA-00349 - Amplifier Cardiac Signals [4] OPA316.pdf |
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