Solar based ECG device with optimal power consumption
The electrocardiogram (ECG) is one of the most important tool for monitoring and diagnosing heart-related diseases. An ECG provides an insight into the electrical activity generated in the heart muscle. ECG devices allow for easy and quick monitoring of ECG for patients who have symptoms of he
2025-06-28 16:36:01 - Adil Khan
Solar based ECG device with optimal power consumption
Project Area of Specialization Electrical/Electronic EngineeringProject SummaryThe electrocardiogram (ECG) is one of the most important tool for monitoring and diagnosing heart-related diseases. An ECG provides an insight into the electrical activity generated in the heart muscle. ECG devices allow for easy and quick monitoring of ECG for patients who have symptoms of heart problems.
To achieve efficient and operable features, individual patient monitoring devices must adhere to several specific requirements: size reduction, mobility, wearable, minimal energy consumption, real-time data monitoring, and processing.Wearable ECG devices usually run on batteries. Due to the small size requirement, the batteries used for ECG equipment often have a limited capacity, and so, must be periodically replaced. This often leads to problems in emergencies, especially for elderly patients.
To deal with this issue, we developed a portable ECG device that uses solar energy as the main energy source so that there is no need to replace the battery. The device can connect to a smart phone or a computer to display the results and monitor the user’s rhythm.To store electricity from solar cells, it is necessary to have rechargeable batteries or super capacitors. A battery has more energy storage capacity than a super capacitor, but the discharge cycle is limited. On the other hand, super capacitors have millions of charging cycles but a lower energy storage capacity compared to batteries. Therefore, for low energy consumption of the ECG, we used a super capacitor to store the solar energy.
The energy optimization issue is of special interest to us. We achieved energy optimization for the ECG device by designing multiple power modules suitable for the characteristics of each main component.
Additionally, we developed an application for tracking ECGs on mobile devices with Windows, Android, and iOS operating systems. For Android and iOS operating systems, the sampling frequency of the ECG device is lower than 400 Hz, the recorded data is processed in real-time, and the results are displayed on the device. For higher frequencies, the data is synchronized on the server and processed by MATLAB (Academic Version R2017b, Mathworks, Inc., Natick, MA, USA) software. For Windows-based software, the operating system is mainly used to collect data with a high sampling frequency, from 100 Hz to 2133 Hz. The data are processed by MATLAB with more complex algorithms for accurate results.
Project ObjectivesFollowing are the main objectives of this project;
1) We want to design a solar-based ECG device that have a smaller size and more mobility (easy to move).
2) To save electricity, we will use solar energy as a main power to operate this device.
3) We use solar harvesting IC for lower power consumption.
4) For achieving highly accurate results, we will design a mobile application that use real-time data to show result.
5) To deal with high frequencies, we process data using MATLAB software.
We design a portable ECG device that uses solar energy as the main energy source so that there is no need to replace the battery. We optimized the design to have a very low power consumption and the current consumption of the sleep mode is only around 40 µA. The device was designed with 24-bit resolution and a sampling frequency up to 2133 Hz that could allow high accuracy ECG measurements.
To store electricity from solar cells, it is necessary to have rechargeable batteries or super capacitors. For low energy consumption of the ECG, we used a super capacitor to store the solar energy.The energy optimization issue is of special interest to us. We achieved energy optimization for the ECG device by designing multiple power modules suitable for the characteristics of each main component. For example, we designed two power supply modules of 1.9 V and 4.2 V for ADS1293 and provided a 1.9 V power supply for both PIC16LF19186 and Bluetooth modules in the sleep mode for the main components.
In ECG monitoring device, up to five electrodes are used to collect three-channel ECG signals from the human body. Five electrodes are attached to the patient’s chest and abdomen. The simple paste method is used to attach the electrodes to the patient. The ECG was designed with four main modules. The first one is the solar energy harvesting module, including a solar panel, solar energy harvester BQ25570, and a super capacitor to store energy from the solar panel. The second module is an analog front-end module with the use of low power integrated analog front-end ADS1293. The third module is Bluetooth with a Bluetooth low energy (BLE) module RN4020. The final module is MCU with the use of an extreme low power (XLP) device (PIC16LF19186) for optimal power consumption.
The recorded signals from ECG device are transmitted to a smart phone or personal computer (PC) via Bluetooth. Application software is developed based on smart phones to observe patients’ ECG signals in real-time. The patient’s ECG signals can also be collected by PC and then data analysis software is used to find abnormalities in the heart rate with a high accuracy. Doctors can use these results for further diagnosis.
We conducted a measurement of the current consumption of the design at different operating modes in the main components. As, operating voltages for PIC16LF19168, RN4020, ADS1293 (digital module) is 1.9 V and ADS1293 (analog module) is 4.2 V. We used Agilent U3606A power supply to create 1.9 V and RIGOL DP832 power devices to generate another voltage supply of 4.2 V. Both devices have an internal built-in current measuring device.
Following are the main benefits of this project;
1) This ECG device is portable and wearable so it is easy to move it.
2) The device have smaller size and have less weight.
3) This device will be operated on Solar Power(this is good for countries especially where there is a power crisis, like in Pakistan).
4) This device have a lower power consumption.
5) Device can also be used in medical camps to facilitate patients (especially in less developed areas, desserts and mountains etc ).
6) This device can also used in sports activities. i.e to check heart conditions of players.
7) The device is also useful for patient who is in home and needs to check-up heart activity on regular bases.
8) We can use this device at any time (there is no need to check that electricity is present or not).
9) This device use real-time data to monitor heart activities, so it gives accurate results.
10) You can display result on smart phone or laptop, as per your choice.
HARDWARE:
Solar energy harvesting:
The main components in design can operate from 1.8 V but to ensure the stability, the operating voltage of the main parts is 1.9 V. The power supply module includes BQ25570 energy harvesting IC, solar cell (2.4 V, 250 m W), and 0.47 F - 5.5 V super capacitor. The BQ25570 is configured with output voltage of 1.9 V to be compatible with all other modules and to optimize the lowest power consumption. The voltage used to charge is 4.2 V with this voltage super capacitor, and it can store more power than the configuration at 1.9 V.
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Design of Low Power Analog Front-End and Bluetooth Module:
For the ECG analog front-end module, we used an ADS1293 chip, which has operating voltage 1.65 V–3.6 V with digital module and 2.7 V–5.5 V with analog module. We configure sampling frequency of chip from 100 Hz to 2133 Hz.
Optimization Power Consumption:
The voltage applied to the main components was reduced to very low levels to allow the smallest current to be consumed. As PIC16LF18196 and RN4020 Bluetooth modules are the two major energy consuming components in this design, they need to be configured to operate in energy-saving modes to optimize power usage. In the normal operation mode, MCU operates in energy-saving mode.
SOFTWARE:
Mobile Phone Application:
We designed ECG monitoring system based on smart phone using low power Bluetooth to communicate with ECG device. We designed a data package and a data transfer protocol for transmission. Each package contains 800 bytes with one or two analog channels and 810 bytes with three analog channels. We can reconfigure the sample rate on the device from 100 Hz to 2133 Hz depending on the number of the input channel.
After connection, smart phone sends start command to PIC16F19186. Then, processor starts to wake up ADS1293 and collect data into buffer; when buffer is full, they send entire data from buffer to smart phone. Then, application performs real-time filtering.
Design FIR Low Pass Filter:
We chose to design FIR filter to eliminate noise signals at 60 Hz. FIR filters have more linear phase rocks, they are more dominant in quantized design and are often deployed in FPGA design or ASIC.
Design High Pass Filter:
Low-frequency components in ECG signals are generated by motion, respiratory changes, and base wandering. The high pass filter does not reduce signal amplitude. However, similar high pass filters have a 5 to 10 harmonic effect on the signal.
EXPERIMENTAL EVALUATION:
Testing Power Consumption:
We conducted a measurement of the current consumption of the design at different operating modes in the main components. As, operating voltages for PIC16LF19168, RN4020, ADS1293 (digital module) is 1.9 V and ADS1293 (analog module) is 4.2 V. We used Agilent U3606A power supply to create 1.9 V and RIGOL DP832 power devices to generate another voltage supply of 4.2 V. Both devices have an internal built-in current measuring device.
| Item Name | Type | No. of Units | Per Unit Cost (in Rs) | Total (in Rs) |
|---|---|---|---|---|
| Total in (Rs) | 52520 | |||
| RN4020 | Equipment | 1 | 1300 | 1300 |
| PIC16LF19168 | Equipment | 1 | 500 | 500 |
| BQ25570 | Equipment | 1 | 3100 | 3100 |
| ADS1293 | Equipment | 1 | 7500 | 7500 |
| solar panel | Equipment | 2 | 300 | 600 |
| super capacitor | Equipment | 2 | 150 | 300 |
| ECG electrodes | Equipment | 6 | 100 | 600 |
| ECG lead(5 leads cable) | Equipment | 1 | 1000 | 1000 |
| header for solar panel | Equipment | 2 | 30 | 60 |
| crystal oscillator | Equipment | 5 | 20 | 100 |
| PCB | Equipment | 1 | 500 | 500 |
| Soldering gun and wire | Equipment | 1 | 500 | 500 |
| plastic body | Equipment | 1 | 700 | 700 |
| Mobile Application | Miscellaneous | 1 | 8000 | 8000 |
| Thesis book and documentation cost | Miscellaneous | 1 | 1500 | 1500 |
| RN4020 | Equipment | 1 | 1300 | 1300 |
| PIC16LF19168 | Equipment | 1 | 500 | 500 |
| BQ25570 | Equipment | 1 | 3100 | 3100 |
| ADS1293 | Equipment | 1 | 7500 | 7500 |
| solar panel | Equipment | 2 | 300 | 600 |
| super capacitor | Equipment | 2 | 150 | 300 |
| ECG electrodes | Equipment | 6 | 100 | 600 |
| ECG lead(5 leads cable) | Equipment | 1 | 1000 | 1000 |
| header for solar panel | Equipment | 2 | 30 | 60 |
| crystal oscillator | Equipment | 5 | 20 | 100 |
| PCB | Equipment | 1 | 500 | 500 |
| Soldering gun and wire | Equipment | 1 | 500 | 500 |
| plastic body | Equipment | 1 | 700 | 700 |
| Mobile Application | Miscellaneous | 1 | 8000 | 8000 |
| Thesis book and documentation cost | Miscellaneous | 1 | 1500 | 1500 |