Browsing by Subject "Low-cost"

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    Low-power transcutaneous current stimulator for wearable applications
    (2017) Gargiulo, Gaetano D; van Schaik, André; McIntyre, Sarah; Breen, Paul P
    BACKGROUND: Peripheral neuropathic desensitization associated with aging, diabetes, alcoholism and HIV/AIDS, affects tens of millions of people worldwide, and there is little or no treatment available to improve sensory function. Recent studies that apply imperceptible continuous vibration or electrical stimulation have shown promise in improving sensitivity in both diseased and healthy participants. This class of interventions only has an effect during application, necessitating the design of a wearable device for everyday use. We present a circuit that allows for a low-power, low-cost and small form factor implementation of a current stimulator for the continuous application of subthreshold currents. RESULTS: This circuit acts as a voltage-to-current converter and has been tested to drive + 1 to - 1 mA into a 60 k[Formula: see text] load from DC to 1 kHz. Driving a 60 k[Formula: see text] load with a 2 mA peak-to-peak 1 kHz sinusoid, the circuit draws less than 21 mA from a 9 V source. The minimum operating current of the circuit is less than 12 mA. Voltage compliance is ± 60 V with just 1.02 mA drawn by the high voltage current drive circuitry. The circuit was implemented as a compact 46 mm × 21 mm two-layer PCB highlighting its potential for use in a body-worn device. CONCLUSIONS: No design to the best of our knowledge presents comparably low quiescent power with such high voltage compliance. This makes the design uniquely appropriate for low-power transcutaneous current stimulation in wearable applications. Further development of driving and instrumentation circuitry is recommended.
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    Open Access
    The Design of a Low-Cost Traffic Calming Radar - Development of a radar solution intended to demonstrate proof of concept
    (2020) Matu, Unathi Neo; Abdul Gaffar, Mohammed Yunus; Janse van Rensburg, Vanessa
    This study aimed to develop a radar solution that would aid the traffic calming efforts of the CSIR business campus. The Institute of Transportation Engineers defined traffic calming as "The combination of mainly physical measures that reduce the negative effects of motor vehicle use." Radar-based solutions have been proven to help reduce the speeds of motorists in areas with speed restrictions. Unfortunately, these solutions are expensive and difficult to import. Thus, this dissertation's main focus is to produce a detailed blueprint of a radar-based solution, with technical specifications that are similar to those of commercial and experimental systems at relatively low-cost. With the above mindset, the project was initiated with the user requirements being stated. Then a detailed study of current experimental and commercial radar-based traffic calming systems followed. Thereafter, the technical and non-technical requirements were derived from user requirements, and the technical specifications obtained from the literature study. A review of fundamental radar and signal processing principles was initiated to give background knowledge for the design and simulation process. Consequently, a detailed design of the system's functional components was conceptualized, which included the hardware, software, and electrical aspects of the system as well as the enclosure design. With the detailed design in mind, a data-collection system was built. The data-collection system was built to verify whether the technical specifications, which relate to the detection performance and the velocity accuracy of the proposed radar design, were met. This was done to save on buying all the components of the proposed system while proving the design's technical feasibility. The data-collection system consisted of a radar sensor, an Analogue to Digital Converter (ADC), and a laptop computer. The radar sensor was a k-band, Continuous Wave (CW) transceiver, which provided I/Q demodulated data with beat frequencies ranging from DC to 50 kHz. The ADC is an 8-bit Picoscope 2206B portable oscilloscope, capable of sampling frequencies of up to 50 MHz. The target detection and the velocity estimation algorithms were executed on a Samsung Series 7 Chronos laptop. Preliminary experiments enabled the approximation of the noise intensity of the scene in which the radar would be placed. These noise intensity values enabled the relationship between the Signal to Noise Ratio (SNR) and the velocity error to be modelled at specific ranges from the radar, which led to a series of experiments that verified the prototypes' ability to accurately detect and estimate the vehicle speed at distances of up to 40 meters from the radar. The cell-averaging constant false alarm rate (CA-CFAR) detector was chosen as an optimum detector for this application, and parameters that produced the best results were found to be 50 reference cells and 12 guard cells. The detection rate was found to be 100% for all coherent processing intervals (CPIs) tested. The prototype was able to detect vehicle speeds that ranged from 2 km/h up to 60 km/h with an uncertainty of ±0.415 km/h, ±0.276 km/h, and ±0.156 km/h using a CPI of 0.0128 s, 0.256 s, and 0.0512 s respectively. The optimal CPI was found to be 0.0512 s, as it had the lowest mean velocity uncertainty, and it produced the largest first detection SNR of the CPIs tested. These findings were crucial for the feasibility of manufacturing a low-cost traffic calming solution for the South African market.