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Bar_graph_temperature_display_dot_mode

2016-12-19 02:01  
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Bar_graph_temperature_display_dot_mode
Fig. 13-9 This circuit combines an LM34 temperature sensor, two LM3914 display drivers, and 20 LEDs to form a temperature display where the temperature is indicated by turn-on of the corresponding LED (from 67 to 86°F). The temperature range can be increased by cascading several LM3419s. The display can be converted from the dot mode to the bar mode, or to flash a bar of LEDs when the temperature sensed reaches a selected limit. This requires a few extra components, as shown on the LM3419 datasheet. Note that the trim values for VA, VB and 1/C are for the temperature range show. UB and VC represent the highest and lowest temperatures, respectively. VA is set for gain of 4 (40 mV/°F instead of the nominal 10 mV/'F provided by the LM34). National Semiconductor Linear Applications Handbook 1991 p 1077.