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Would this circuit work? (power supply board)

crumblechris

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Hi everyone,

I've been designing circuits for about 3 hours, so please forgive me if I've done anything wrong. I'm using the software provided by Fritzing, largely because it is free and exports to Gerber files, which I'll want to use when getting the pcb's made apparently.

There are two traces on this board which are on the bottom layer. From the left side of R2 to the via, and from D2 to D1 to the via. That is meant to be part of a full bridge rectifier, which will take AC in (240v) and output DC, then it'll be used to power a series of LED panels which will make up a word or name etc....

So two questions;
Would this work?

Is this a sensible way of doing it? Am I missing something silly here?
--- Updated ---

It's worth mentioning, I know the ground pin goes nowhere right now. I NEED to sort that out and may well use a ground fill to do that, but the software I'm using seems to have some issue with the ground pane working as I'd expect (it doesn't isolate one particular trace for some reason.
 

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andre_teprom

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Would this circuit work?
You did not provide component values, only general footprints do not properly depicts what is there, besides not giving any clue if it was well sized. BTW, the circuit in the printed shape is not the suited way to show, one would expect the diagram form as well.
 

    crumblechris

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crumblechris

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Hi Andre,

I'm slightly confused, other than component values, which can be changed depending on the loads being put through the screw down terminals, R1 is 470oam and r2 is 6.9k. (those are for the 1 LED and the capacitor pulldown).

This is very much a prototype board, and currently is sized to be 85mm width and 57mm height. But that is purely based on the measurements with Fritzing.

I understand that I am very very new to this, so any guidance would be really gratefully received.

Does that help? What else do you NEED to help me? I'm interested in knowing that if I were to get that pcb printed, would it electrically work "as expected" i.e. all of the connected would get a DC supply based on the voltage supplied in the AC power in, with the LED lighting when power was applied, separately to when the individual screw down terminals were used.

What else do you want?
 

wwfeldman

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it is impossible to determine if something is going to work without
knowing what it is supposed to do.

as andre said, please show the schematic, with part values for resistors and capacitors, and part numbers for the semiconductors.
and please write a few lines about what you expect your circuit to do
 

crumblechris

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Hi Andre,

If it helps, this is the sketch I made of the circuit I wanted to produce.
 

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crumblechris

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It's a power board which will go on to provide power to 8 other boards, each with LEDs used to spell out a word, in the next version I also want to add USB charging and a few other fancy things like a rolling LED strip, but that requires chips and stuff, which I don't have.

There are no semiconductors that I'm aware of. The capacitor is 220nano at 400v. The Resistors for the LEDs are both 6.8k, and the one for the capacitor is 470.

Does this get you any closer. I'm a very practical person, and honestly have never done this before, so thanks for holding my hand through it!
 

andre_teprom

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I'm unable to understando your drawings, hopefully others will give you usefull insights. BTW, you did not specify what is the power that will be delivered to these boards, what is their consumption, varying, constant? what is their input tolerance ? As you can see, the question is incomplete at all.
 

crumblechris

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Hi Andre,

the drawing should be relatively easy to understand. I drew the resisters as boxes instead of their proper symbol, for which I apologise, but I would have thought that, plus the full bridge rectifier at the start of the circuit, I would have thought it would have been relatively simple to understand.

As for the power consumption of each of the boards, at the moment I'm not 100% sure, as it will depend on the LEDs in each board, how many, etc..., but my plan is to TRY and keep them all to less than 300mAh each, but again these really shouldn't be an issue as the resistors in line can be changed.

All I really want right now is for someone to check that I've not missed any traces and what Ive done generally makes sense.

It appears you are not willing to do that, and for someone who has been looking into this for less than a day, and has only ever followed a few kits in electronics previously, I was hoping that the community would be slightly nicer to me than has been the case. I am very sorry I am not a professional with 20 years experience building PCBs. This is something I'm doing as a one off project for my son, and wanted to make sure I was going in the right direction before committing to getting any PCBs made.

Thank you for all of your help and your effort to look over what I have done.
 

andre_teprom

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If I got it correctly, you added a 6K8 resistor in parallel with the 240vac, which will make it dissipate ~8W, to much for any kind of resistor placed in a PCB. Another point to remark: Seems like you are not considering a transformer, which could put your and other's life in risk. Seriously, your effort to make this working is admirable, but you shoud review the circuit carefully, perhaps first describing what is the exact function of the circuit, is it intended to be a pilot indicator of load connected from each board?
 
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FvM

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Some observations.
The PCB wiring is different from the schematic.
1. Your schematic claims 240 VAC input, the PCB has a low-voltage jack
2. In the PCB, there's no LED between input and rectifier, instead a meaningless (shorted) RC combi
1594135264554.png

3. "I drew the resisters as boxes instead of their proper symbol" Would be fine if you did either, instead we see some kind of chicken scratch.
1594135365066.png
Anyway, we know now what you mean.
4. The intended circuit function is still unclear
 

betwixt

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Additionally, consider the the required value of the series resistors depends entirely upon how much current each +/- output has drawn from it. As it stands the voltage is DC but varying from about 0V to 320V at a rate of 100 times per second. That probably isn't really what you want. The amount dropped by the series resistors is 'Vdrop = Load current/Resistance' so you get full voltage under no load current and lower voltage as more current is drawn. With varying voltage and no regulation and also no AC line isolation you circuit will never work properly.
Brian.
 

wwfeldman

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It appears you are not willing to do that, and for someone who has been looking into this for less than a day, and has only ever followed a few kits in electronics previously, I was hoping that the community would be slightly nicer to me than has been the case. I am very sorry I am not a professional with 20 years experience building PCBs. This is something I'm doing as a one off project for my son, and wanted to make sure I was going in the right direction before committing to getting any PCBs made.
no one is disrespecting you
no one is being mean to you

schematics are a very specific language that communicate a lot with few symbols and a little text
when you use non-standard symbols it makes it difficult to understand the question(s)
also, we tend to look at questions from all angles, so the "what is it supposed to do" goes beyond
"is my PCB ok?" to is your device going to work - the device will not work if the circuit is not correct, even if the PCB is perfect

please recall that in your first post, you wrote " Would this work? "

the best help comes from the best information - so we ask questions

so the resistors are boxed squiggles
what are the circles labeled + and -?
i rotated your schematic so the text was up-side up
then the input to the FBR is on the bottom - two resistors, a capacitor and an LED -
what is connected to the two filled in circles connected to LED1 and the capacitor?
there are three open circles near the switch - how are they related to the switch
is the switch SPST? SPDT? momentary contact? toggle? or something else?
why is the switch after the FBR and not before?
 

Easy peasy

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C1, R1 do nothing as presently laid out
--- Updated ---

other than that it may well work - good luck ...!
 

KlausST

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Hi,

I can't recognize different layers.
Thus if all traces of the PCB in post#1 are in just one layer, then the rectifier output is short circuited.
Maybe there are jumper wires, maybe not....
Maybe you did care for this, maybe not....

We want to help. But it's really diffcult...

Klaus
 

Akanimo

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Hi,

I looked at your work yesterday and I spotted a lot of things, which would be addition to those that have already been pointed out. And they were basically about the safety of the user.

I support your courage to want to take up challenges, and above all, your decision to seek advice. That shows that you are being careful and people like to help careful people, and I believe members here are willing to help. I guess that's the reason members are responding in the first place, and coming up with questions directed to you.

You said that you are "very very new to this [electronics]" and it kind of shows in the way you put up your diagram. Furthermore, it is very important to ask for certain information about your work because there are safety concerns, and I am going to point to a few of them in a minute.

Some key information that you have given are that you are making this device for your son, that the part you are showing to us is a power board that is supposed to provide power to some other boards, and that those other boards bear LEDs displaying spelt words. With these level of info coupled with the level of knowledge and skill (on the subject) that you present to us, I could only come up with certain assumptions: your son (child), spelling (learning aid, in other words, a toy).

So my first point of concern why making a toy powered off the mains. Why not battery. Assuming that the level of ingress protection is adequate at first, and everything is working 'perfectly', there is this likelihood that your son could toy with his toy and break it and gain access to live parts. A matter of life and death.

Now, taking a look at your schematic, and even assuming that it is not a toy, there are no protections like fuses, galvanic isolation, etc, and then there are these connectors that seem to constitute an access to live parts. You also showed us a board layout. Irrespective of any other thing that's happening on the board, what about creepage and clearance? We certainly cannot tell about that by merely looking at your layout like so. Do you know how many layers of protection is required at a minimum for devices powered off the mains? Irrespective of any other point, on your schematic, you showed the connectors (the access to live parts) connected before the resistors which to some extent can limit current. That's no way near to being a good idea. Now, assuming all safety requirements are met, after your bridge rectifier, you should have a capacitor to filter out the pulsation of the bridge-rectifier output voltage, that you do not have.

What I have mentioned, adding to what others have, are just a few of the concerns. But it's a lot of typing already.

Looking at everything, as presented, holistically, my advice to you would be that you not make this power board. I strongly recommend that you do some more learning and take up less risky projects if you have to. You could start with enrolling in some form of electronics training and taking some courses.
 
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andre_teprom

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Your schematic claims 240 VAC input, the PCB has a low-voltage jack
In addition to FvM's remark regarding the unsuited socket, since the plug on the board is likely female and the male connector is on the cable, it would expected that an harzardous voltage will be present at a live beak, not safe. As a general rule, it is the opposite, the supplied energy is present at the female housing.
 

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