Limit Sensors

This sensor inventory is back in limited quantities. I have more supplies arriving soon so the availability will increase. Its been difficult obtaining supplies but the availability is returning.

This version is identical to the previous version in all ways except size. The board 35% smaller (15.5 mm x 20.5), most importantly the same easy connect block remains. See the short video of the new version in action.

This is a magnetic sensor (Hall Effect Sensor) designed to be used in place of mechanical limit switches for CNC Routers 3D Printers or any movement control system. They are highly accurate and offer consistent repeatable results with extremely low tolerances.

Hall effect sensors are used for proximity switching, positioning, speed detection, and current sensing applications. In its simplest form, the sensor acts as an on/off switch when it comes in proximity of a magnetic field. In this case the sensor switches on when a magnetic field is present and off when the field is not present.

I designed these switches to be used on my ShapeOko CNC router with the standard GRBL controller (supplied with ShapeOko 1 and 2) they will work on either 3 or 5 volts. These sensors can also be used anywhere position detection is required such as a lids, windows, doors and anything where position detection is needed. Feel free to ask me about your situation.

How do they differ from mechanical limit switches?

• There are no moving parts to wear out and fail.
• They offer a much higher accuracy than a mechanical switch.
• They offer more flexibility in placement/configuration.
• They have three connections (Sensor, Positive and Negative). Where the mechanical limit switches just have two (Sensor, Negative).
• They are cool, lights to show current alarm status. Green = Normal, Red = Alarm

How Do They Work:

The functionality is very simple, when the sensor comes in proximity of magnetic field, the sensor trips, electricity flows between the signal pin and Negative (GND) on the CNC controller. This is exactly what happens with a mechanical limit switch when the lever is pressed. You can simulate this by simply connecting a wire from the sensor pin and the negative pin on any of the ShapeOko controllers. If the Limit setting is enabled, movement will stop the instant the connection is made.

When the sensor trips:

• A negative signal is sent via the signal pin
• Green LED turns off.
• Red LED turns on.
• In the case of a CNC router movement stops.

When the magnet is moved away from the sensor the state is reversed:

• A negative signal is sent via the signal pin.
• Red LED is turned off.
• Green LED is turned on.

The sensitivity and precision of the magnetic sensor make it an excellent choice for accuracy and repeatability, especially where tolerances of .001 mm or less are required. The sensor will have no impact to the controller since it requires very little power.

Product Details

• Each unit is assembled and tested prior to shipping.
• Dimensions are 24.13mm x 20.32mm
• Input voltage 3 to 5 volts.
• The sensor features simple push in wire connector, no soldering or crimping required and simple disconnect.
• Optional holder is 27mm x 23mm Green or Black. Insulates the sensor if you need to mount on a metal surface.
• Optional Round Neodymium Rare-Earth Magnet 1/2in diameter 1/8in thick.

Connecting The Sensor

Connecting the sensor is very easy there are only three connections. As noted in the picture of the sensor with the wires plugged in

• Red wire goes to Positive
• Black wire goes to the Negative

The sensor wire (White) is the wire that sends the alarm state to the controller. Its connected axis alarm pin of the controller. In the case of the GRBL controller that comes with the ShapeOko this would be:

• Pin 9 for the X axis
• Pin 10 for the Y axis
• Pin 11 for the Z axis.

As noted earlier the wires push right into the wire connector, no soldering or crimping. The connection is strong and can easily be released without any damage (see video below). You can use solid or stranded 20 to 26 AWG wire. I recommend 22 AWG stranded wire flexible and easy to push in to the connector.

The following are videos of the sensors:

• Connector Howto https://youtu.be/eUy-GG0JFg4
• Grbl Shield Demo https://www.youtube.com/watch?v=F3XpLWkOgSw