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Linear Over-Voltage Protector

An historic method of handling an over-voltage problem from a failed voltage regulator or alternator was to electronically drop a short circuit across the line with a big SCR. This technique was called “crowbar” since it was like short-circuiting bare wires with a crowbar. Dude...!

The old crowbar method was very reliable since it forced a fuse or breaker to blow, disconnecting the circuit. But then again it blew a fuse or breaker…and some think this is inelegant and introduces its own problems, such as Godzilla-like current surges and induced load dumps, even if it is kinda…well, Macho…!

OV protection is critical since an errant high voltage will not necessarily blow any current-activated circuit protection devices, while it can do extensive damage to your electronics.

But we make a tiny domino-size module that monitors the voltage on the main bus (or anyplace), lights a panel-mounted warning LED when the monitored voltage rises above 16.2V for more than 200 mS and politely opens (disconnects) the alternator field circuit or B+ contactor (or whatever). A user-supplied over-ride switch (wired to E-BUS+ or battery bus) will reconnect the circuit, and if held in will even keep the circuit on. A "Mom-Off-On" switch might be nice, too—if you really want complete control!

It can be mounted by double-sided tape or bonded to a small attachment plate, or bolted as desired. A resistor or potentiometer in series with the external LED for dimming can be used but is not required.

Basic Specifications: Dimensions: 1.03” X 1.50” X 0.30” (26 X 38 X 8 mm).
Weight: about 1/2 ounce (15g)
Connectors: 0.250” male Faston tabs and 5-pin Molex locking connector (mating plug supplied).
Over-volt warning and trip level 16.20 +/- 0.15 V
Maximum Voltage Input=18 VDC nominal
Maximum Allowable Continuous Current = 5A

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