and here is the schematic.
Creality.4.2.7.-.Schematic.28-5-22-1.pdf (193.7 KB)
That was the answer I thought you were going to sayâŚ
Question though, the box of ledâs I purchased on Amazon indicated the ledâs were rated at 3.1v and 20mA. I did do some tests of the ledâs using various resistors, and the 2.2k won overall (that was at full 24v), and we have since then determined a smaller resistor will work just fine in conjunction with the buck and ldoâs.
but I am at a loss on âtrying it first - 10mA might be enoughâ.
How would I test that, would it be a different resistor?
Yes, you generally still need caps on input and output of regulators (switching or linear LDO), and it depends on the part so you need to look at the datasheet.
In general, a 0.1uF ceramic on input and output is always used and sometimes an extra âbulkâ cap like 10uF added on in and/or out as well.
Some regulators specify a minimum capacitance needed on in or out â some specify a maximum on the output. Look at the datasheet.
Switching regulators add ânoiseâ to the output, which could be something on the order of 20 to 100 mV or so of spikes and crapola at switching freqs (eg one of the above parts switches at about 700KHz). That high-freq noise is not a problem for something like a motor driver system. It can be an issue for sensitive analog circuitry or even some digital circuitry.
Look at the rails with a scope â on ac coupling you can zoom in to see the switching noise. This is always the first thing to do when bringing up any new circuit. If you donât have good power there is no point to test anything else. If you donât have a scope, get one. There are decent entry-level ones from siglent, rigol and less-decent ones from hantek⌠Anyone who tries to work on anything electronic without a scope is going to get frustrated.
A buck reg is there to do a major voltage step down efficiently (ie, without wasting a bunch of energy to heat). When you follow a buck with an LDO you will clean up the noise with the LDO. Example: use a buck to drop your 24V supply down to 5V to get a kinda-noisy 5V rail, and then run that to a 3.3V LDO to get a clean supply for digital stuff. There is heat loss with the LDO, but it is not too bad in this case as the âdeltaâ drop is 5V - 3.3V = 1.7V and if you are pulling letâs say 100mA out of the LDO the loss is 1.7 x 0.1 = 0.17W (pretty low).
Also, when you hear âLDOâ that means low-drop-out regulator. This is a modern wat to make a linear regulator, and they only need a minimum delta of a couple of hundred millivolts typically. Compare that to the 50-year-old LM78xx family which needed something like 3 volts minimum delta. If you ran 24V into a 7805 to generate a 5V rail and draw 100 milliamps, you will have a regulator loss of (24 - 5) * 0.1 = 1.9 watts. That is a lot of heat to dissipate, and the reg may need to be bolted to a chunk of metal or have a heatsink. Donât waste you time with ancient 78xx parts.
The best advice you got was @SteveT pointing out how to draw a logical and readable schematic. That is always a good starting point.
And yeah, leds are generally perfectly fine with a milliamp. Some new ones are so efficient the can be way too bright until you cut the current way down.
Iâm struggling to understand your question, so I apologise if Iâm telling you something you already know.
You have two options for powering the LED in question: 1/ from the 24V supply with a 2.2k 0.5W resistor (which will deliver about 10mA into the LED), or 2/ from a buck regulator. You say that you have already experimented with running the LED from 24V and arrived at the same value resistor (2.2k) as I calculated, so calculation and experiment agree: 10mA is a good value for the current. Therefore I donât understand why you are asking about it again.
When I said âtry it firstâ I meant connect the LED to the 24V supply via a 2.2k resistor, which will result in about 10mA flowing in the LED. Then remove the 2.2k resistor and fit a 1k resistor instead. That will result in about 20mA in the LED. You should decide whether the brightness is sufficient with the 2.2k resistor, or if you need the 1k resistor. So âtry it firstâ means trying different values of resistor. It sounds like you have already âtried it firstâ.
The second option is to use a voltage regulator (specifically a switched-mode buck regulator). Disadvantages are that it takes up a bit more room and adds complexity, so might potentially be a little less reliable. The main advantage is that it doesnât run hot.
If you decide to use a buck regulator, then you would be daft to use one with a 12V output. The LED requires 3.1V, so the obvious choice would be a buck regulator with 5V output (or possibly even a 3.3V output). Assuming a 5V regulator, you will need a resistor which will drop 5 - 3.1V = 1.9V with a current of 10mA (which you have determined by experiment to be a good value, remember?).
R = V/I = 1.9/0.01 = 190 ohms. Closest convenient value is 180 ohms.
Letâs calculate how much power that resistor will dissipate:
power (watts) = volts^2 / resistance = (1.9 x 1.9) / 180 = 0.02W.
0.02W is a trivial amount of heat, so you could use a small 0.25W resistor. This illustrates how using a buck regulator greatly reduces the amount of energy wasted as heat.
Speaking with my Reliability Engineer hat on, I know that a resistor is pretty much the most reliable of electronics components, so if it were me I would still use a 2.2k 1W resistor to power the LED off the 24V supply. Itâs an industrial setting, so wasting half a watt of power is too trivial to worry about. Also, the temperature of the resistor is unimportant provided itâs spaced off the board. And finally, reliability is particularly important so using a resistor instead of a buck regulator is appropriate.
In fairness to @teletypeguy, an argument can be made for a buck regulator. Both approaches will work. You decide.
In closing, I suspect I still havenât explained the LED current properly. Could you rephrase your question and I will do my best to help.
I hope I am going to be using this the proper way, but it wonât hurt to try anyway.
To @teletypeguy, and @SteveT, I wanted to let you both know I have not fallen off the planet, I am still here.
Been working on the schematic a bit, symbols table ALLOT, and envisioning how to begin the putting things together. some sample parts have been rolling it the past couple of days, and a couple look promising.
Iâve decided to go with a push on, push off illuminated power switch.
I also received the PWM fan module, seems simple enough. Except they used a weird connection on the board for the fan to connect, using over-size pins, spaced out wider than most. So Iâm going to come up with a comparable female connector, or some other avenue.
Anyway, I will get to each of your latest comments over the next day or two.
Thanks guys for all your effort and contributions.
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To @teletypeguy and @SteveT , hello gents.
For the past few hours I have been reading the comments SteveT laid out for me, and before I go any farther, I wanted to give you my shopping list for your perusal and Stamp of Approval.
But first I have a question. At first I was considering just a couple of resistors and leds in the right spot and be done with it. Reason: Generation of noise. I figured the small amount of noise that could be generated would not be soo much to be an annoyance.
Is my thinking noise generated to be that bad?
I also considered your comment regarding analog vs digital noise. I would like to have the most effective auxiliary board, without breaking the bank of course.
So, thinking my last sentence is of benefit, then here is what I plan on purchasing for this projectâŚ
Voltage Regulators (Linear)
595-UA7812CKCS. Here is the link on Mouser.com. https://www.mouser.com/ProductDetail/Texas-Instruments/UA7812CKCS?qs=DcvZ7Fltd5zyvhYGYzcR7A%3D%3D
595-UA7824CKCS. Here is the link on Mouser.com. https://www.mouser.com/ProductDetail/Texas-Instruments/UA7824CKCS?qs=0O%2FZFlpUpJW8ScG6LUngmA%3D%3D
Low Dropout Regulators (LDO)
595-LP5907QMFX-3.3Q1. Here is the link on Mouser.com. https://www.mouser.com/ProductDetail/Texas-Instruments/LP5907QMFX-3.3Q1?qs=asCBFxFfL1RsL2VYqGFsBQ%3D%3D
Buck Converter (DC-DC)
VXO7805-1000. Here is the link on Mouser.com. https://www.mouser.com/ProductDetail/CUI-Inc/VXO7805-1000?qs=HXFqYaX1Q2zTUq5iRuYtuQ%3D%3D
Apparently on May2nd, I referenced this link. Iâm doing it again because I want (hoping) this will be my final components shopping list.
One last question. teletypeguy, your post on May 3rd, the screenshot, Figure 4.
+VO and -VO. The two representations of the capacitors, what is the reason for the + symbol on top vs under the capacitor?
Well, I lied, this the last question. During the search process for the different components, I noticed that 24vdc was rarely listed as an option. 24v was listed all over the place. I know there is a difference between AC vs DC voltage. If some of the components I listed at the beginning only show as an option 24v, do I need to start all over again my component searching?
Awaiting your comments, before I continue updating the schematic.
( I apologize to everyone if my schematic skills lean towards the unprofessionalâŚ
Never used KiCAD before, never used any schematic drawing program before. The only schematics Iâve drawn out entailed running a 12AWG wire from the main panel, to a junction box, then onto an outlet in another room)
@teletypeguy, wanting to ensure that I get apples to apples components, I did some surgery on the new main board.
after pulling the heat sink off what I discovered to be 3 regulators, after a bit of cleaning, I found the specific part number. I found a website where I could download the datasheet. I will attach below.
A very large portion of the info is way over my head, but I was hoping you would be able to check the specs, especially the amps. I know that if the circuit is pulling higher amps than what is designed for, things will fry and melt.
Could you compare the attached datasheet to the datasheet I will attach in the next comment and give me your expert. opinion. Are they comparable?
HY1403D.PDF (1.5 MB)
Boy, where to start? I am not fully certain what it is you are trying to do, though I appreciate the research and learning you are putting into it.
First off, why do you need a new power distribution board at all? I modified my Ender printer to swap in a 32 bit card, add second Z, direct drive extruder and all that, but it was a simple swap and used the original 24VDC, 14.6A, 350W power supply. The front panel ribbon could be extended to re-locate, but if desired.
You originally you are using a 3-to-36V 2A supply, and you want to drop that to 24V at an unspecified current, and then down to 3.5V for some reason (did you mean 3.3V or 5V?). If you are planning to feed that 24V to the printer motor drivers you do not have enough current.
But then later you said you would not use the 3-36V supply, and use the printer 24V supply. So I am confused as to why you would still buy a 7824 regulator at all.
If you put a linear regulator like a 7824 to drop the 36V down to 24V, it will get super frickinâ hot â letâs say you pull 1 amp out â the regulator will dissipate (36-24)*1 = 12 watts! Of course it will stop producing heat pretty soon as it self-destructs 
Yes, a heatsink can be used, but the point is, a linear regulator (like 78xx) is not appropriate for major voltage drops and current levels.
Your question about the cap+ being on top or bottom in one of the screenshots: The + indicates a polarized cap like an electrolytic or (conflict-mineral) tantalum. That screenshot showed both a positive-output regulator with cap positive on the output, and negative-output regulator with cap positive on the ground. Negative regulator is a totally different application.
The part datasheet you provided was a power mostfet, not a regulator. Totally different.
If I were you, I would not worry about laying out a pcb just yet because it will likely come back wrong, need changes, and you will get disillusioned. You need to learn some basic electronics, and just start with a breadboard, some parts kits, and do some bench work. Scribble your schematics on paper for a while. Blow some parts up. Thatâs how I started back in the 70s.
Check out the learning sections at adafruit.com â LadyAda (Limor Fried) is an amazing engineer and she built an awesome company to get people into electronics/programming⌠Another good place is sparkfun.com. There are lots of tutorial sites out there.
https://www.adafruit.com/product/239
https://www.adafruit.com/product/184
https://www.adafruit.com/product/2975
https://www.sparkfun.com/products/13973
I donât want to dampen your enthusiasm for the project, but you should breadboard (or just solder-tack) and have a working prototype before laying out a pcb. IMHO.
Iâm afraid the answer to both of those must be âNoâ. I am not sufficiently qualified, experienced or knowledgeable to make those judgements.
Iâm going to say something which I fear you will find offensive, but none is intended and I say it in a constructive spiritâŚ
From the nature of your questions, I donât think you should have taken on this task because itâs too far away from your current level of expertise. You are trying to run before you can walk. You are relying far too much on the expertise of complete strangers. And now asking them to approve your entire bill of materials, part by part, and then study and interpret the datasheet for you because âa very large portion of [it] is way over [your] headâ is asking too much.
You need to take ownership of this yourself. You need to do your own research. You need to read some books, do some online training on basic electronics, and work your way through a few simple projects in order to build up your expertise. Forums are not a substitute for months of learning or training, nor are they the right place to get âproject sign-offâ because you are in over your head.
I said you need to get some basic learning under your belt first. If you insist on cracking on with this particular project, break it into little parts and use those as experimental learning aids. Experiment with driving an LED using different values and wattages of resistors, then a linear voltage regulator, then a switched-mode buck regulator. Compare the results. When you are confident youâve got one small part right, move on to the next part. Eat the problem one small bite at a time.
Edit: As an aside, I donât think you are even very clear on what your requirements are yet. Thatâs fine, and itâs how lots of projects begin. There is a process called âRequirements Captureâ, and often it is done by prototyping small parts, trying them out, refining them, or sometimes dumping them and starting again. As you work through the options and possibilities, the requirements become clearer. The key point is that you donât want to move on to the design and development stages until the requirements are reasonably well understood, otherwise it gets expensive and wasteful of time and effort. (This is not how Agile development works, but youâve a way to go yet before thinking about that.)
Before you know it you will have a solution which you have arrived at using your own brains, rather than someone elseâs. And then, if you still have questions or uncertainties, come back to the forum with specific, focussed questions that donât require a lot of work from the contributors.
Your enthusiasm and commitment is admirable, so donât let me put you off the whole thing. I just think you will benefit more from climbing the learning curve from the bottom than jumping on part way up, especially if you are piggy-backing on someone elseâs learning.
In summary:
1/ I think - in your most recent post - you are expecting too much;
2/ I donât have the necessary expertise to help with enough confidence;
3/ Itâs too soon to concentrate on the solution when your requirements still seem unclear;
4/ I think you are trying to run before you can walk, and I urge you to undertake some structured learning in electronics basics.
HOWEVER, this is just me speaking. 
Perhaps someone smarter and more generous than me will come along to help. Meanwhile, I wish you the very best as you work your way up the learning curve. You will gain immense satisfaction from it.
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@SteveT , @teletypeguy , @Seth_h
To you three gentlemen, I wanted to say I really appreciated all your input during the past couple of weeks. I am truly sorry for the part I played in taking a simple upgrade and turning it into an enormous undertaking. For the part I played in ( as SteveT put it ), relying on the input from strangers to go over my parts list and approve, review the datasheets, etc.
I am truly sorry I laid that burden at your doorstep.
I went back and reviewed my original topic and text regarding this project and saw that it could have been worded differently. With what I put out there started me on the path to self destruction. The only thing that came out of the in a positive way, was I learned a great deal. I also learned I still have a great deal to learn.
Which is why I took a look at Adafruit ( thank you teletypeguy ), and found a great deal that peaked my interest.
With what I have learned from the past weeks, I have made on final adjustment to the schematic. Chopped a couple of things, moved a couple others, and came up with something that could work.
Iâll find out when the DIY PCB Kit arrives. I have plenty of ledâs, resistors, capacitors, and voltage regulators to play with and burnout while I test the new schematic.
Again, thanks for the pep-talk. It was what was needed.
Over the next few weeks, I will post some updates of how the PCB comes along based on the schematic, as well as the continuing modifications to my control box design, and how I get everything wired and functioning. Once this is all done, I still have to flash the firmware and get it right.
(Ok, so got halfway through the long thread before I hit the tl;dr; threshold!)
Quick (and dirty) solution to running two 12 volt fans from 24 volts, and is exactly what youâd see in 99% of cheap commercial designs: just put them in series, and run them from 24 volts!
(This is the same sort of trick used in the past, youâd have two 120volt mains fans: in parallel for US operation, in series for European operation!)
Just a couple of points. Firstly, youâve wired D2 and D3 in parallel again, so they will always do the same thing (ie indicate the presence of 12V from the regulator). One of them is redundant.
Next, I canât work out what U4 is meant to be; if itâs a bridge rectifier it appears to be connected incorrectly. Perhaps you could tell us what it actually is.
Why are you using polarised sub-1uF capacitors around the regulator? Can you even buy a polarised 0.1uF capacitor? Anyway, you should be using ceramic capacitors for those two. Only use polarised (electrolytic) caps if you need to add something of higher value (eg 10uF).
Why are you using the same value dropper resistor for both the 12V and 24V LED indicators? As shown, you will get twice the current in the 24V LED as in the 12V ones, so they will have different brightnesses. I donât believe this is what you want.
You are still repeating the mistakes you made right at the beginning. Itâs as if youâve taken on almost none of the advice youâve been given. I explained at length how to calculate the correct value LED dropper resistor for the two supply voltages, and yet you are still using the same value for 12V as for 24V. I explained at length that the two 12V LEDs were in parallel, and thus one was redundant, and yet youâve made the same mistake again.
Donât even think about the PCB yet. The schematic is nowhere, and your level of understanding isnât much better. You need to prototype it on breadboard first.
Iâve reluctantly concluded itâs a waste of time coaching you because you apparently listen to almost none of it. I spent ages writing my previous post where I beseeched you to undertake some proper, structured, bottom-up learning before doing this project; where I explained how you donât even have a clear idea of the requirements, let alone how to fulfil them. You came back with âthanks for the pep talkâ and then posted another schematic with the same old mistakes. It wasnât a pep talk, it was an essay on the harsh realities.
As a result, Iâve decided to step out of this thread at this point. I will close by saying:
-
calm down
-
take a breath
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think about what you are trying to achieve
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read properly, and think carefully about, all the advice youâve been given in this thread
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extract the key points and write them all down in your own words
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buy some breadboard and some components and do some experimenting
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as it becomes clear what you actually want, and what is actually possible, write it down as your own little Statement of Requirements (the purpose of this being to discipline your thoughts, not for others to read).
Your enthusiasm and commitment will take you a long way in life, but you need to work on your other attributes as well. Good luck and best wishes.
This long thread has been mostly about other things than using KiCad and the forum is for KiCad, not for general electronics or learning electronics. Advice and pointers have already been given abundantly. Therefore the thread will be closed soon.
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