Monitor Magnetic Fields with Honeywell’s SS411A

Switches tend to wear out as time goes by – the Hall effect provides a nice alternative to detect “presence”. Honeywell’s sensor division provides an interesting set of devices in the SS400 and SS500 families.

The neatest feature of the whole sensor family is their ability to work with wide supply voltage ranges – voltage inputs from 3.8V to 30V are acceptable. The open collector output should be well-known from I2C drivers, and makes circuit integration really simple. Thermal sensors compensate the hall sensor’s behavior over a thermal range from -40 to 150 degrees centigrade.

…Honeywell provides a set of example schematics for sensor interfacing

In terms of magnetics, various types of switching behavior are provided. The SS411, which saw a large amount of search interest recently, is a bipolar part. This means that it is tuned to both North and South-facing magnetic fields – one of the benefits of this approach is that the part can sense closely-spaced magnetic fields of different polarities.

Physical placement is significant when using polarized Hall effect sensors…

In addition to that, unipolar and latching parts are also available. Unipolar parts such as the SS441 trigger only when receiving a positive (south) field, making them ideally suited to detecting lever positions and similar problems. A latch enables and disables itself only on the presence of specific fields – if a south field enables it and disappears, the device will stay switched on. Latch, unipolar and bipolar parts can be ordered with various switching sensitivities, which – for example – enables you to use high sensitivity sensing when air gaps are large.

Honeywell shows itself extraordinarily flexible when packaging is concerned. In addition to through-hole sensors with various physical pin arrangements, the SS500 family packages the same sensor technology in an SMD case. For example, the SS511AT is but an SMD version of the SS411…