Extruder Indicator RGB Enhancement

Do you have an extruder indicator lacking in impact? Do you enjoy modding your printer? Do you have a habit of adding LEDs to everything?

Then do we have the thing for you!

Introducing the RGB Backlighting Enhancement for your Extruder Indicator. Simply print and prepare two small 3D printed circuit boards as well as the magnetic position shaft and you've got an RGB platform for whatever spinner you want to attach.

If you're interested in how I went about making the initial design, that livestream can be found here: https://youtu.be/7h2bQytEU2Y

How it Works

This device mounts to your extruder and features two circuit boards. The first board is an IO and level shifting board. While it is designed specifically for the Prusa i3 MKS series (working with the printer's filament runout sensor cable), it only actually requires a 5-volt circuit which is likely available on most printers. This board splits the input directly into an output header- which returns to the filament sensor- and then through two voltage dividers to get the required voltages for operation.

The ground and these two lowered voltages are then connected to the second board, which sits in front of the extruder. This board features a series of analog Hall Effect sensors which control the color and brightness of the LEDs mounted around them. This is achieved by mounting an array of magnets on a shaft which runs from the extruder's shaft like any other Extruder Indicator. An Indicator can then be mounted to the exterior face of the shaft.

Project Prerequisites

Experience soldering electrical components is recommended. Soldering with a 3D printed board can be difficult as you cannot solder directly to the PCB.

Tools

• Soldering equipment (soldering iron, solder, etc.)
• Driver for M3 bolts
• Recommended: 1mm Drill bit to clean up PCB holes (and drill or dremel which can hold the bit)
• Optional: Hot glue gun with hot glue sticks (for potting/insulating connections, as mentioned below)

Materials

• Filament (more info in the printing section) 
• Glue for attaching magnets
  • While you can use whatever sticks, I advise using a thin glue (i.e., super glue) on the magnet for the 8mm shaft as I found thick glue (I tried hot glue) can cause the magnet to sit unevenly and this can stop the shaft from spinning

Components

• 2x 47-ohm resistors
• 1x 100-ohm resistor
• 1x 220-ohm resistor
• 4x Common Cathode RGB LEDs (Preferably frosted so the color mixing is better; I had clear)
• 3x 49E Analog Hall Effect Sensors (Note these are different from “switch”-type Hall Sensors)
• 4x 8mm x 3mm Magnets 
  • optional- 2 additional magnets to attach Indicator to back of Thru Shaft)
  • Having extra magnets can help fix problems you may run into; see FAQ
• Wire to connect components and boards (I used pieces of 28-gauge ribbon cable)
• Male and Female Dupont Connectors (required to connect back to filament runout sensor, and optionally for easy disconnection between the Powerboard and Indicator board)

Hardware

• 2x M3x16 bolts (for assembling the 3D printed parts)
• 2x M3 nuts (for assembling the 3D printed parts)
• 2x M3x35 bolts (to replace stock M3x30 bolts)

Assembly

Print both PCB's and the Mounting Plate (print recommendations in the next section). Remove the top two bolts from the front of the Extruder and use the two M3x35 bolts to bolt the Mounting Plate to the Extruder.

Before we start assembling the PCBs, we are first going to do a dry run of the components to make sure everything is lined up. Glue an 8mm Magnet onto the end of the 8mm shaft of the Thru Shaft. Next, bolt the two PCBs to the Mounting Plate by placing the Indicator PCB in front of the Extruder and the Powerboard above the Extruder. Use M3x16 bolts through the front of the Indicator Board to do this and countersink the M3 nuts into the Powerboard for the bolts to connect to. Once they are attached you can run the Thru Shaft through the Indicator PCB and connect it to the Extruder's Shaft. Unload any filament you have in the Extruder and move the Extruder (via menu or serial terminal) to confirm that the Thru Shaft moves freely with the Extruder shaft. Once you are sure there are no issues, you can remove the Thru Shaft and PCBs from the assembly and move on to assembling them.

After cleaning up the PCBs (including drilling out the 1mm thru holes for the components), begin assembling the Powerboard based on the images below:

For my board, I mostly used the leads of the resistors themselves (and lengths I trimmed off them) to make the connections. I also potted the leads with hot glue to make sure they didn't accidently short against the top of the Extruder (mostly me being paranoid; the board is held a few millimeters above the motor and probably won't make contact).

The second PCB (the Indicator PCB) gets connected as shown below. 

Essentially: Connect all ground terminals. Connect 3.5v to Red Hall VCC and 4v to Green+Blue Hall VCCs. Connect each Hall to its corresponding LED pin on each RGB LED. 

On my board, I tried something a little different: I first completed the ground circuit. After checking to make sure the circuit was not shorted on anything it shouldn't be, I insulated/potted the circuit using hot glue, leaving a long lead uncovered to attach to later. I then connected the VCC's for the Blue and Green Hall Effect Sensors and extended the lead to near the Ground lead. After extending the Red Hall Sensor's VCC to join them, I connected these three leads to a ribbon cable and made sure all 3 circuits and the ribbon connection was potted/isolated. I then connected the Red anodes of the LEDs in parallel to the Red Hall Effect Sensor's output, checked to make sure nothing was shorted against anything it shouldn't be, and- once again- potted the circuit. I continued this process for green and blue in turn and was therefore able to wire the PCB without using extra insulated wires. There are two downsides to this method, however: 1) it can be extremely hard/impossible to fix any mistakes you made; and 2) depending on how you route everything and how much hot glue you use, the circuit can be a lot thicker than simply crisscrossing insulated wires.

Once the circuit is built if you have not attached a cable to the Indicator Board yet, do so and then reattach the boards to the Mounting Plate as explained above. After attaching the boards to the Plate, connect the cable from the Indicator Board to the outputs on the Powerboard. Make sure that you are making the correct connections: 4v output to Blue/Green Hall Effect sensor lead, 3.5v output to Red lead, ground to ground.

Unplug the Filament Runout Sensor and plug its connectors into the Powerboard PCB. You may need to extend the wiring, and make sure you are connecting it in the appropriate orientation (the order is 5v, Output, Ground; Ground is closest to the edge). Connect the Powerboard's open output (labeled “FIL” in the first image, “F” on the “Powerboard with Text”) to the Filament Runout Sensor- again, ensuring it is plugged in the correct orientation.

Setup mounted and with all 3 connections. As you can see, I added an extension cable between the stock Filament Runout cable and the Powerboard.

Ensure all LEDs light up and each Hall Effect Sensor produces a different color light by moving a magnet's North Pole in front of the sensors. You may see a slight red light when no magnet is present; this is simply the nature of the design. Note that the sensors will not visibly trigger on the South Pole of the magnet.

Next, we'll be assembling the Thru Shaft.  First, we want to double check that the Thru Shaft is still moving freely when fed through the Indicator PCB. Once you are done, begin gluing the three magnets into the magnet array. When doing so, make sure that the North pole is facing out and the South pole is embedded in the print; as mentioned above, the LED's will only light when the Hall Sensor detects the North Pole, and you can check which side that is by moving the magnet in front of the Sensors while they are powered. Finally, if you would like to attach your Spinner/Indicator to the Thru Shaft using a magnet, glue that magnet in now. If your Indicator already had a magnet attached, make sure to orient the magnet on the end of the Thru Shaft correctly to attract that magnet. If you are not using a magnet to attach your Indicator, you can attach it to the Thru Shaft however you like at this time.

Finally, push the Thru Shaft through the Indicator PCB so that the magnet on its end connects to the shaft of the Extruder.

Now start a print and enjoy the Light Show!

Printing

Recommended Print Settings

• Layer Height: .2mm
• Supports: 🗵
• Brims/Rafts: 🗵
• Material: Higher Temp. Filament Preferrable

The features on this print are all quite generic and there is no significant stress being put on it, so a generic .2/15-20% profile should be fine. For the same reasons, virtually any filament would be fine, but choosing a higher temp material lowers your chances of damaging the board while soldering.

The one exception to this is if you happen to have a printer/printer setup that can actually handle the resolution necessary to print the 1mm holes in the PCBs at their correct size. In this case, use whatever settings you need to if you want to avoid post-processing the boards. Also, if you can print at such a fine resolution, you can likely print the “Powerboard with Text” instead of the “no Text” version successfully; as the name implies, the PB with Text model has all the components labeled, but the text is too small to reliably print on most printers (well, my printer with a .4 nozzle, at any rate).

Post Processing

As mentioned above, for most printer setups the PCBs will need all their thru-mount holes drilled out. While a smaller tool would be easier to do this, I have done this many times (on other projects) using a full-sized drill gun, so don't worry if that's all you have (just note that, in that situation, it's easier to move the print into the drill rather than pushing the drill into the print).

Reproduction of this Project

Several things need to be stated here:

• 3D Printed circuit boards are not ideal
• Buying the components are more expensive than the per-piece cost makes it seems
• Not everyone who would want to add this mod to their printer has the experience or equipment necessary to do so

Acknowledging all these points, I want to state explicitly and emphatically that I fully support any Maker who wants to put together and share/distribute a schematic/gerber file that others can order from a PCB service, as well as any company that wants to professionally manufacture a formal product. You don't need to ask: just go for it. I think this is a really cool printer mod and it would make me happy if everyone who wanted to add it to their printer had the opportunity to do so.

Notes and Tips

• Remember to follow common safety precautions- this includes having a filter for fumes while working on the PCBs
• While assembling the PCBs double check all your connections at every point; nothing is worse than finding out at the end that you accidentally shorted a connection
• When drilling out the PCBs, you should be able to feel the indent where the hole is supposed to be; you can use this to center the drill bit
• I did the soldering without a stand/clips/helping hands, so it is doable. As a tip, if you are using solid wire to make a connection you can melt the center point slightly into the plastic to keep it in place while you apply solder to the ends
•  Try soldering with a lower temp than you normally use in order to reduce the risk of melting the PCB
• If you are trying to find an alternative power source for the board, remember that hotend fans don't always run 100% (and therefore are not suitable)
• While I've updated the models to have more space since I built mine, still try to keep your wiring close to the PCB so it doesn't get squished against the stepper. If the Indicator PCB is pressed against the Stepper, then it will cant the central shaft and bind with the Thru Shaft. Alternatively, your circuits could short against the motor

Alternative Designs/Remixes

If you're feeling adventurous, here's some ideas you might try out

• I wanted to do this completely with an analog circuit, but you could use a microcontroller. This would let you implement different logic or patterns on the LEDs. One example I can think of is decoupling the brightness from the position of the magnet and instead setting the brightness based on the speed of the Extruder.
• I believe there is enough space to go up to 8 LED's and 6 Hall Sensors if you wanted them (but don't quote me on that). 
• Rather than wiring the same colors in parallel, you could go down to 3 LED's and wire each color combination in parallel for each Hall sensor: in other words, Hall 1 out is wired to LED1-Red, L2-Green, L3-Blue; H2 out is wired to L1-Blue, L2-Red, L3-Green; H3-> L1-Green, L2-Blue, L3-Red. If I'm thinking of this right, it would produce a “chaser” pattern where the colors follow themselves around (though maybe add more LED's and Hall sensors as above).
• You should be able to implement this using a through-hole pot/encoder on the shaft, but I'm not entirely sure about how to design a circuit to segment the analog output. 
• I took a quick look at motor encoders to simplify the design, but most of them are solid (so you can't attach a Spinner to the other side); maybe you will have better luck.

FAQ/Troubleshooting

• The Thru Shaft isn't spinning/is getting stuck at specific points
  • I'm preempting this question because I ran into it myself and am assuming it's a related to how I assembled the PCB (and therefore not something that everyone will experience). I found that adding a few more magnets (3 in my case) to the end of the Thru Shaft (they don't need to be glued on- just let them hold themselves together) fixed this problem. Since this pushed the Magnet Array on the other end away from the Hall Sensors my LEDs were dimmer. To fix this I simply stacked another magnet onto each magnet of the array and the LEDs were back to full brightness.