Color Change Alert Box for 3D Printer

On my single extruder 3D Printer, I sometimes want to change the filament color mid-print. In the past, I had to visually inspect the print progress and check the printer to see if it has paused.

This Alert Box now sounds a horn and turns on the alarm light so that I know when the printer is in the Home position. I have set up my printer to go to the home position when it has been paused or has completed a print job.

The cost was less than $30 for all parts, but could have been done for less than $5 by eliminating the horn, power switch and the timing relay.

Video of operation can be found on my YouTube channel (JABA 3D)
Here's the link to the video: ALERT BOX by JABA 3D

Micro Limit Switch (<$1)

Light (~$3)

Timing Relay (~$14)

Alarm Horn (~$7)

Power Switch (<$1)

The power supply on my printer is 12VDC. So, I chose parts that were compatible with that.

The Limit Switch was positioned next to my Y-axis home limit switch so that it comes on at the same time without interfering with the other limit switch. When in the home position, the switch is wired to the Timing Relay's trigger input for sounding the horn. It also powers the LED Light directly. I have considered using the Normally Closed contact on the limit switch to power a Run-Time Meter. This would be used for tracking actual print time.

The LED Light is on anytime the printer is in the Home Position.

The Timing Relay's purpose is to only trigger the Horn briefly, so that it isn't obnoxious. I have set the Timer to only turn on its output for 0.3 seconds. Just enough to get a chirp. However, the Timing relay has multiple options, so I may consider having it chirp every 5 minutes, in case I don't hear the first one.

The Power Switch was put in to disable the Alarm Horn, in case I am printing at night. (Don't want to disturb the family!) It only disconnects the horn, so the light will still come on for a quick check.

The Alarm Horn will only chirp as allowed by the Timing Relay and the Power Switch, as mentioned above.

Even before I made the Alert Box, I had to make sure that I could tell the printer to go to the home position when the printer job was complete. To do this, I created a 2-layer object and printed it. As it turned out, the offset for my Y-axis does not go to the home position. I believe this is in the firmware of my printer. But, there is a work-around for it. Each time I power up the printer, the first thing I do is home the printer and then set the Home Offset. This is a manual operation for now until I take the time to figure out what I can do with either the firmware or within the GCode settings.

Now that I know I can send the printer to the home position, I need to make sure that printer pausing works for my printer. It does. To do this, I use the "Pause at Height" post processing plugin within Cura. In the settings, I Park the Print Head at 0,0. (Note: since I am only using the limit switch for the Y-axis, I could park the X anywhere.)

Now that I know that I can park the printer on the limit switch, I built the box and tested. SUCCESS !!!

I plan to do another Instructables soon on how I do Single Extruder Color Changes. Follow me for more 3D Printing Adventures.