Designated the OAR Series, these open-air through-hole devices consist of a custom-engineered resistive element welded to copper leads with integral stand-offs from the PC board. Copper leads minimize the resistance shift caused by solder wicking, which often occurs with single alloy resistors when excess solder forms on the base of the resistor. Even a small amount of solder wicking on competing single alloy components can alter the resistance value of the device in the circuit by as much as 30%. In contrast, the welded copper leads in IRC’s OAR Series are forgiving of the inherent uncertainty in actual post-solder wick connection points. As a result, IRC’s OAR customers enjoy precision performance in a demanding environment.
The unique form factor keeps the “hot spot” of the resistive element safely off the PC board and allows air to circulate under it, allowing increased heat dissipation and cooler operation. The OAR Series resistors are used extensively in automotive current-sense applications due to their rugged construction and high power ratings. As more automotive subsystems require current-sensing for small electric motor control, power regulation or safety circuits, design engineers are specifying the OAR Series resistors where competing technologies are unable to handle high current, or where a flameproof alternative to organically-molded axial devices is needed.
Automotive applications for the OAR Series resistors include current sense, feedback and surge protection circuits in ABS systems, window lift and sunroof motors, wiper controls, body computers, power steering systems, seat belt pre-tensioners, fuel pumps, heated seats, flasher modules and solenoid controls. The component is uniquely situated to support the automotive industry’s increasing usage of small electric motors for motion control and energy monitoring.