My astronomy project:
Design of a 3D-printed filter wheel

Content:

1. CAD design of a filter wheel
2. Chassi
3. Stepper motor
4. Gears
5. Shaft and Roller bearings
6. Home position sensor
7. Lid
8. Off-Axis guider
9. To be continued

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

6: Home position sensor

To let the driver know where the filter wheel stands it must have some signal. A home position sensor will make that. Every time it parks at home it will know where it's, from that point it count the steps to come to each filter.

Home position sensor:

Another found in my desk, an optical position sensor of fork design. It has the dimension: 14 x 10 x 6 mm with a 5 mm gap. I have other even smaller optic sensors if this one doesn't fit. All these parts come from scrapped printers and computer mouses, the old ones with a rolling ball.

The home switch needs a barrier with a hole to work. Here I have extended the rim and made a hole in it. First outcast for a home hole where the senor can shine through. A circular hole of 1.5 mm diameter. But with this design it will be problem even with small wobbles of the filter wheel.

Better with an elongated hole, let the wheel wobble a bit and still get the signal from the sensor. I have extended the hole to 1.5 x 3 mm. I also had to rearrange the place of the 3 mm filter mounting holes to get room for the optical fork sensor. I'm not really satisfied with this solution, the extended rim takes space where the later off axis guider will sit. Maybe I change it to a magnetic sensor.

3D-print:

The sensor's rectangular hole looks good, it should work as it is.

The optical sensor fork will sit like this and be mounted at the lid above.