As connectors evolve, even the most simple of accessories, such as jumpers and shunts, do the same. For the most part, size and materials make up their evolutionary path.
Jumpers are small and typically constructed of non-conductive plastic used to open and close an electrical circuit when connecting and disconnecting electrical contacts. The plastic material ensures that unshielded jumpers do not short-out live circuits accidentally. These contacts—or jumper pins—exist in groups called jumper blocks, consisting of at least one pair of contact points. A conductive sleeve—or shunt—is placed over the jumper pins and a contact is made. They are used to set up and/or configure PCBs and are found on a broad base of boards, I/O cards, hard drives and more. In the past, PC systems used jumpers to activate such settings as speed and voltage. They also set the operating mode for ATA drives. These devices have been in use since the dawn of the PCB. Common terminology regarding jumpers refers to such aspects as “open,” if at least one pin does not have a jumper, and “closed” when a jumper is covering two or more pins.
Examples of available jumpers include the Cinch 95B two-contact jumper with a straight-body orientation for rectangular connectors. The jumpers are for connecting between adjacent or alternate terminals and are comprised of brass with nickel plating. The Keystone Electronics “True” zero-ohm 5110 SMT Jumpers feature a .028 mm-thick copper finish with silver plating. The material of this Keystone jumper is all conductive polystyrene that meets ANSI/EIA-481 standards, while the Molex 380021290 terminal-block jumper is sized at 74.3 mm long x 15.1 mm deep and 1.6 mm high and is also EU RoHS-compliant.
Shunts, by comparison, allow electric current to pass around any section of a circuit, thereby creating a low-resistance path. A shunt can have multiple jobs. For example, it can protect a circuit against overvoltage; high currents through a shunt will trigger a circuit breaker or fuse. Shunts are also used to bypass a defective device, whereby if there is a failure of one element in the circuit, a shunt can be used to pass around the defective element.
An example of a shunt is the TE Connectivity’s 382811-2 female shunt that is EU RoHS-compliant and features two contacts and a 2.54 mm pitch. With a straight-body orientation and stick packaging, this device has a maximum current rating of 3 A per contact and an insulation resistance of 1000 mOhm. The housing material for this particular shunt is polyester, and the contact material is made of phosphor bronze with gold-over-nickel plating. Dimensions are 5.08 mm long x 2.54 mm deep x 6.35 mm high.
The Samtec SNT-100-BK-T-H female shunt features two contacts and also has a 2.54 mm pitch and straight-body orientation. The maximum current rating is 4.3 A per contact and maximum contact resistance is 5 mOhms. Materials include polyester for the housing, phosphor bronze for contacts and tin-over-nickel contact plating. Dimensions are 50.8 mm long x 2.54 mm deep x 14 mm high.
There are a wide range of jumpers and shunts spanning from micro- to high-profile that address several board and connector types and applications. These jumpers and shunts represent an important element in connectivity and mirror the evolution of connectors.