For maximum social isolation, driving alone is clearly ideal, but this is not widely practical or environmentally sustainable, and there are many situations in which two or more people need to drive together. Most megacities (e.g., New York City) support more than a million of these rides every day with median figures of 10 daily interactions per rider ( 4). ![]() ![]() One common and critical social interaction that must be reconsidered is how people travel in passenger automobiles, as driving in an enclosed car cabin with a copassenger can present a risk of airborne disease transmission. They are redefining a myriad of social and physical interactions as we seek to control the predominantly airborne transmission of the causative, SARS-CoV-2 ( 1– 3). Outbreaks of respiratory diseases, such as influenza, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome, and now the novel coronavirus, have taken a heavy toll on human populations worldwide. Our findings reveal the complex fluid dynamics during everyday commutes and nonintuitive ways in which open windows can either increase or suppress airborne transmission. An airflow pattern that travels across the cabin, farthest from the occupants, can potentially reduce the transmission risk. We estimate relative concentrations and residence times of a noninteracting, passive scalar-a proxy for infectious particles-being advected and diffused by turbulent airflows inside the cabin. Here, we present results from numerical simulations to assess how the in-cabin microclimate of a car can potentially spread pathogenic species between occupants for a variety of open and closed window configurations. A passenger car cabin represents one such situation with an elevated risk of pathogen transmission. *This indicates the inverse of the signal.Ī similar version of this article appeared in the issue of Electronic Design.Transmission of highly infectious respiratory diseases, including SARS-CoV-2, is facilitated by the transport of exhaled droplets and aerosols that can remain suspended in air for extended periods of time. Unlike peak detectors that use a capacitor to hold the output voltage, this design includes a digital potentiometer (IC1) that holds the output level indefinitely, without droop. It holds the output level indefinitely, making it useful as a long-term memory. The primary advantage of this circuit is the complete absence of such output droop. ![]() ![]() Most peak detectors employ a capacitor for holding the output voltage, and the droop (slow change) in V OUT caused by the capacitor's leakage current is particularly noticeable with low frequency or low duty cycle signals. By reducing this V OUT range, the size of an LSB can be decreased, thereby increasing the output resolution. V OUT ranges between the voltage levels connected to the upper and lower extremes of the digital pot (5V and 0V in this case) in 32 equally spaced increments. When V OUT reaches V IN, the comparator output goes high and latches V OUT at that level. When V I rises above V OUT, the comparator output (IC2) swings low and selects IC1, allowing the wiper position to increment upwards with each high-to-low transition of the clock (INC*). In an alternative approach, shown in the figure below, a 5-bit digital potentiometer with a servo loop is used to create an inexpensive peak detector with a logic-level reset input and no output droop.Ĭomparator control of IC1's chip-select input ensures that the digital potentiometer becomes active only when V IN exceeds the V OUT level currently latched, and R1 ensures that the potentiometer increments upward (rather than downward) as a result. Most peak detectors employ a rectifier and a sample-and-hold circuit, which is prone to output droop.
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