Rotating device (jog mechanism)

Since electronic equipment has been more sophisticated and versatile recently, highly operable input devices are required. We introduce some rotating devices (jog mechanism) using Hall effect ICs here.

Rotating device using Hall effect ICs (jog mechanism)

Advantages of using Hall effect ICs for jog
1．　The rotation amount and rotational direction can be identified.
2．　High durability due to non-contact detection
3．　Highly resistant to contamination such as dust, dirt, or oil, because of detection of magnetism

Principle

When a multi-polar magnet is rotated, the north and south poles can be observed alternately at a certain point near the magnet.
If Hall effect ICs in two different latch types are placed at locations where the phases of magnetic field change are offset by approx. 90 degrees, High (H) or Low (L) repeated signals offset by approx. 90 degrees each other can be obtained.
When the leading edge of one Hall effect IC is used as the reference, the rotational direction of the magnet can be identified depending on whether the other Hall effect IC signal is H or L. In addition, counting the number(s) of pulses of one or two signals can identify the rotation amount. Therefore, it can be said that the rotation amount depends on the number of poles on the magnet.

Configuration examples

Here, two typical examples of the jog configuration using Hall effect ICs are introduced.

 Configuration 1 Ring-type magnets are placed so that the rotational axis of each magnet is normal to the PCB for the Hall effect IC during the operation. If the pitch between the magnet poles becomes small, sometimes the Hall effect ICs cannot be placed at adjacent locations where the phases are offset by 90 degrees. However, there is no problem to configure them at locations a few poles away, provided that the phases of the output signal are offset by 90 degrees.

Configuration 2
Roller-type magnets are placed so that the rotational axis of each magnet is parallel to the PCB for the Hall effect IC during operation. If the magnet diameter is small, sometimes the Hall effect ICs cannot be placed on the same circumference. However, there is no problem to configure them at locations offset in parallel with the rotational axis, provided that the phases of the output signal are offset by 90 degrees.

Recommended applicable products

The following products are available to provide a jog mechanism.

All-time drive type: EM-1711, EM-0711
Pulse-driven type: EM-1712

Configuration and how to select product

Latch

Actual records
Cellular phone, digital still camera, etc.