ULN2429A

The ULN2429A is rated for operation with a load voltage of up to 30 volts. Selected devices, for operation up to 50 V are available as the ULN2429A-1 .In all other respects, the ULN2429A and the ULN2429A-1 fluid detectors are identical.Primarily designed for use as an automotive low coolant detector,the ULN2429A monolithic bipolar integrated circuit is ideal far detecting the presence or absence of many different types of liquids in automotive, home, or industrial applications. Especially useful in harsh environments, reverse voltage protection, internal voltage regulation, temperature compensation, and high-frequency noise immunity are all incorporated in the design.

Features of the ULN2429A are:(1)high output current; (2)AC or DC output; (3)single-wire probe; (4)low external parts count; (5)internal voltage regulator; (6)reverse voltage protection.These devices are furnished in an improved 14-lead dual in-line plastic package with a copper alloy lead frame for superior thermal characteristics. However, in order to realize the maximum current-handling capability of these devices, both of the output pins (1 and 14) and both ground pins (3 and 4) should be used.

The absolute maximum ratings of the ULN2429A can be summarized as:(1)supply voltage:-50 to 16V;(2)storage temperature range:-65 to +150;(3)operating temperature:-40 to 85;(4)output voltage:30V;(5)output current:700mA.A simple probe, immersed in the fluid being monitored is driven with an ac signal to prevent plating problems. The presence, absence, or condition of the fluid is determined by comparing the loaded probe resistance with an internal (pin 8) or external (pin 6) resistance. Typical conductive fluids which can be sensed are tap water, sea water, weak acids and bases, wet soil, wine, beer, and coffee. Non-conductive fluids include most petroleum products, distilled water, dry soil, and vodka.The probe can be replaced with any variable-resistance element such as a photodiode or photoconductive cell, rotary or linear position sensor, or thermistor for detecting solids, non-conducting liquids,gases, etc.