3D Printer ReWire Upgrade and PCB Integration

UPDATE: I realize there is a ton of info below, but I would appreciate if someone could just comment on the schematic at the end of this post. This would help me tremendously.

New to the group, but with all group members I hope to learn from you as well get some good info regarding a project I started over 10 months ago.

It all started with my 3D printer and a simple main board upgrade, but over the months it has escalated to much more. Primarily, a total rewire to include an external control box where all wires connect.
I have the beginnings of the control box (3D printed on another printer) completed, with the new upgraded main board installed.

Honesty Check… I am not an electrician, nor electrical engineer. But I am willing to learn if only someone would point me in the right direction. Most of what I have completed so far has been with the help of Google.com, and youtube.com
But I am now at the stage where even those don’t help, I just don’t have the background. This is where relying on the members of the group comes in.

Here is my next milestone, the creation of a schematic / auxiliary PCB and get power down to the main boards connection points. This is where power for all motors, sensors, fans etc, is drawn fdrom.

Here is where I am at on the first electronic milestone.

I have a power supply: Input 100v - 240v AC. Output 3 - 36v DC, 2amp using a DC plug

See Below for pics of specific parts

The DC Plug fits into the power jack, which is soldered onto the new printed circuit board (PCB). that I am attempting to create using KiCAD software for schematics and PCB creation.

Power is applied to the circuit board, it then flows through voltage regulator (24v max), through a push on / push off switch.

Power then flows through a resister/s or another voltage regulator (dropping voltage down to 3.5v DC), while a branch circuit will run to a 2 position terminal block, the wires then run down to the main board power terminal block.

As I mentioned before, I am way over my head, out of my comfort zone on this.
I would like to ask one favor though, and if you do respond to my need for assistance, please try not to use electrician terminology or language that will just confuse, and lead to numerous messages back and forth for clarity.

With that said… Here is my schematic thus far. Any suggestions welcomed. Also would like input on using capacitors before and after the voltage regulator, saw several references to this practice.
Was going to show the parts I was going to use, but new users only get one imbed object.

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In general, the best advice you will receive when starting is to follow the datasheet example implementations. They are not always 100% accurate, but they are generally the best data you’ll find until you have developed experience with a specific part.

In this case, your datasheet requires an input capacitor if the DC source is located an “appreciable distance” away from the DC/DC. Since you are using a plug, this qualifies as appreciable. So put a 0.33uF input capacitor between pins 1 and 2 of your LM7824.

Output capacitor (between pins 3 and 2) is recommended but your datasheet says that they need to be at least 0.1uF.


Thank you Seth for the reply, I think I may have seen the same article as you. But I wasn’t for certain they were necessary, but your reply fixed that.
I have a capacitor kit (varying sizes) coming. I’ll add the capacitors to the schematic.
Would you mind another question? On this aux board, I am wanting power to a fan that sits at the top of the new control box.
Question? The regulator in the schematic outputs 24vdc, the resister in front of the LED will bring that 24vdc down to 3-5vdc Is this part of the schematic correct? Or should I just use a regulator to bring down the vdc to 3-5vdc with a resistor to fine tune the voltage??
Regarding the control box cooling fan. It is 12vdc also. I will have to run a second voltage regulator for this fan, identifying a LM7812vdc as a choice to install (with accompanying capacitors). Does this make sense?
Specking of regulators, will I be required to have a separate voltage regulator for each circuit even if the voltages are the same
IE: I have the resistor, and led hooked up and right now it is the only item on the board. But if I add a circuit for the 2nd fan, as well as an identical LED circuit, can I just have one regulator and branches to the two led circuits?

I hope I am not imposing.
Give me a couple days to draw up the schematic changes, and additions for your review.

Using a series resistor for a LED is common practice, even from a 24V power supply, but you do have to keep some things in check.

For the LED. Led’s are diodes, and they have a relatively fixed voltage drop that is in between 0.9V (for Infra red diodes) to around 3V for Blue Leds. The voltage drop of the led is pretty much determined by the color (an electron has to have enough energy to generate a foton when it jumps the gap, and energy of a foton determines it’s color (this is grossly simplified)).

So assume 2V over the LED, then R1 will have 24 - 2 = 20 volts over it, which results in 20/1k = 20mA which is a lot for modern leds. 20mA was common for LED’s 30 years ago, but modern leds often have a much higher efficiency and 1mA is probably plenty.

Power dissipation in the resistor is IIR = 0.02 *0.02 *1000 = 0.4W and a lot of resistors are only rated for 0.25W, so your resistor is likely to overheat. So use a resistor that has a minimum resistance of 2k2. Also, do some tests beforehand and adjust the resistor to get the amount of light you want from your LED. You will probably end up somewhere between 2k2 and 22k. Things like this are easiest to experiment with on a breadboard.

No, you can add multiple devices in parallel, as long as the voltage regulator has a big enough heatsink and you stay below it’s maximum current rating.

Sorry, I have quite a few questions to ask as I’m fairly ignorant of 3D printers.

Exactly what does this power supply run. Does it run the whole printer (motors, heaters etc.), or just the control panel?

What other voltages and current ratings are needed to be supplied?

An LM7824 will supply 1 amp of current absolute maximum. Is this enough?

You have a variable output power supply (3 - 36V) @ 2amps. Can you adjust this to 24V, thus eliminating the 24V regulator?

Is the 2 Amp supply enough to run everything you intend to run on the printer?

Thank you for the input. First off, the LED’s I purchased are from BOJACK, and is a kit (multiple colors) all in clear glass. I was going to use RED for the following:
RED for main power ON
RED for main fan that sits atop the control box
and RED for the extruder fan, the chamber that heats the filament. Each filament has heating requirements or ranges, so the fan helps control that range, along with electrical control.
and finally RED for the cooling fan, which blows air onto the hot filament as it is pushed through a nozzle onto a flat bed one layer at a time. Controlling the amount of force from the fan can either make or break the project. Too little cooling and the filament remains molten too long thus causing the project to sag, while too much cooling causing the new layer to not adhere to the previous layer properly thus causing cracking to occur.
Anyway, the led’s spec’s are: 3mm, I/VF: 20mA/2-2.2v LI: 1000 - 2000 mcd
I do have some led’s with a VF rating of 3-3.2v which I may use if the brightness of the 2.2v is too low.
I am also not set on ALL RED led’s, my use a different color for each fan.
I bought a breadboard set, I can test some of the led’s and determine what resistor would be needed. I’ve got 400 of them so if a few get blown - oh well.
I’ll start with a 1k and test, and in increments of 1k, increase the resistor and eventually narrow down the best resistor to use.
Question??? Power dissipation, minimum resistance of 2k2. What is 2k2?
Also, if I increase the resistance, is that not also going to limit the flow of electrons to the led causing it to be dim?

Thank you for jumping in on this, is really appreciated.
As for the power supply, it is 24vdc to the main board connection port, and from there it is de-ivied up amongst all the other functions. The motors are minimal draw on the power.
Those other functions would be: 3 fans with an amperage ratings ranging from .10a to .13a
The two biggest hogs would be the heating chamber for the filament and the heater for the bed surface. My biggest mistake was not taking a voltage or amp reading beforehand. I am fairly certain I can connect the display controller, along with the hotbed and extruder (heating chamber) and get some readings without connecting up the other cables.
As for the 3-36vdc variable adapter. I think I am going to drop this from the plan. I can still use the power supply installed in the base of the printer. It is rated at 120v AC, 350watts MAX, with 3 lines for 24v DC if needed. At the present, there is only one24vdc line used.

1k = 1000Ω 2k2 = 2,200Ω 47k = 47,000Ω 330k = 330,000Ω
0R1 = .1Ω 1R2 = 1.2Ω 15R =15Ω
1M = 1,000,000Ω 4M7 = 4,700,000Ω

R replaces the decimal point
k represents X 1,000
M represents X 1,000,000

Edit by paulvdh.
I edited this post. Prefix for kilo (10 to the power of three) is the lower case k.

What is the purpose of the upgrade?

On the subject of LEDs.
Over-bright (hard driven) LEDs become annoying over time. They will also have a short life. They may suit and survive for an hour on a breadboard, but you may find you need to replace them after perhaps 10 hours, maybe 50 hours, in the machine. Paul’s calculation for minimum resistance of 2K2 (2,000Ω) should be accepted.

here is an updated schematic, with two major changes.
First I moved the ON/OFF switch between the power jack and the C__in1 capacitor.
Second i added two bus bars after the V0 3 capacitor, one for line lines, the second for neutral.

I hope they are used properly…

Purpose of the upgrade is multi-fold.
First, the main board. Has drivers for the X - Y - and Z motors. The original board drivers when moving the various axis, was quite annoying. New board is much quieter.
Two, the primary control display was physically attached to the base of the printer. I wanted a display which had a much longer ribbon cable so I could sit back in the chair and control the functions.
Three, update of the display pcb to provide much more functionality.
Four, the mini computer control box, wanted to have something external to the base, all wiring external for ease in troubleshooting and replacement. All connections will now run to a power jack on the back side of the tower, where the corresponding connection on the back will connect to the appropriate port on the upgraded main board.

As for “should be accepted”, I am taking in all comments and recommendations. I am fish out of water here, but I am learning you and everyone else, there is no discounting of anything on my part.
And believe me, I appreciate every comment, you’re taking the time to read what I am doing and replying, so I don’t want anyone to think their effort is wasted.

For beginners it’s always a good learning experience to blow up some led’s and overheat resistors. I once had a led literally explode just because I connected it to an electrolytic capacitor charged to around 30V, and I’ve burned my fingers on resistors that got from cold to glowing red hot in less then a second.

These days I am more on the careful side. I’d rather start with safe values (for example a 100k series resistor) and then lower the value until I get the wanted result. In some cases I even wear safety glasses when powering on a circuit for the fist time. But now I’m getting older, I find myself wearing glasses more often anyway.

Well, lucky me. Didn’t blow a single LED

I ran several tests, 3mm and 5mm LED’s, 5 different colors. Started with 100k resistor and worked my way backwards. Worked my way down to 3.3k and 2.2k.
The following table shows the voltage I received at the anode side of the LED with a constant 24.2vdc from the power supply. Personally I am leaning towards using the 3mm LED’s because the voltage at the anode side is better grouped, ranges are closer together.

Anyway, what you think?

Screenshot 2024-04-30 at 10.04.39 AM

Use a 4R7 resistor; but don’t hold on to it or the LED when you apply power and watch the magic smoke come out! :rofl:

Hmmm, sorry, I couldn’t resist that comment. :smiley:

The caps look fine. I would be careful because that on/off switch will blow a fuse/start a fire when used in this manner. :wink:

You will want it place it inline with the positive power line.

You are also connecting your positive output to your ground next to R3.

FWIW, stepping down your 24V to 12V using a resistor for your fan will only work if your fan has constant 1k impedance (which it does not). You need a DC/DC for the 12V output that will regulate the voltage level independent of the current draw.


Just a few points I noticed too, firstly let me reiterate what @Seth_h has said and your main switch is ‘across the supply’ and will cause a dead short :scream: so move that asap. Secondly D1 and D2 will light at the same time and I presume they are meant to show a connector is active (Live) so a rewire there perhaps :slightly_smiling_face: R3 is indeed shorted to ground which has been mentioned. R4 and R5 could be made to form a 'potential divider to half the 24v down to 12v but I dont know anything about what these connectors are going to be used for except ‘Fan’ of which I no nothing so hard too say and would recommend a re think of that one. You could remove the resistors and label them as 24v outputs and deal with whats plugged into them in another part of the project. You could of course add another regulator something like a LM7812 and you have a regulated 12v output :grinning: Hope this helps a little and good luck !

I’m placing a screenshot up front with the changes you mentioned. Did I make the correct modification?

Now, " You need a DC/DC for the 12V output that will regulate the voltage level independent of the current draw." What is a DC/DC you mentioned?
Also, I invested in a: DONGKER Fan Temperature Controller Module,DC 12V 24V 48V 4-Wire PWM Driver Module for PC Fan/Alarm . Found it on Amazon, and seems to be just what I need for the 12vdc pwm fan inside the control box.

Weblink in case you want to read about PWM card.
" https://www.amazon.com/dp/B083R9KX83?psc=1&ref=ppx_yo2ov_dt_b_product_details "

The other two fans are small, 12 v, >0.10a, two wire (not pwm) so connection is simple.

Hello mousey, glad you helping me out.
I just sent an updated screenshot of the two questionable points seth made.
Switch is now inline, and the over by R3 has been removed.
Do you concur with my changes?
Also, I need to sit down and really read your other remarks, to see if I can make sense of it, so for now thanks, but I’ll have to get back to you…

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Yep, those changes are correct and no problem :grinning:

OK mousey, here is the updated schematic. D1 and D2 are now I believe on separate lines (independent). Fixed R3 short.

Could you explain to me about “R4 and R5 could be made to form a 'potential divider to half the 24v down to 12v”, or maybe annotate on the schematic to explain.
\For the moment, this aux board will supply 24vdc to the 3D printers main board(J1).
I am trying to determine the best way to go on the three fans. I am waiting for a specialized board for the control box main fan which is PWM capable. It requires 4 wires, but the printer main board only has two contacts for each fan.

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