The schematic appears to be on the bit of paper behind your PCB :P If you're asking for a general solution, it's lots of painstaking busy-work - catalogue all the components, remove 'em from the board, get a high res scan of both sides of the board, load up your EDA software and make it semi-transparent, and go from there.


Yes I know I have the schematic, I was just curious about the process in general. Thank you for the tip, I’ll look into it.


There probably is not a single "the process", but here's what I would do: * Get a list of all components (BOM) * Add them to a schematic in KiCad, make sure to choose the right annotation. If you let KiCad do this automatically, R10 might not be R10 anymore. * Connect them in a way that makes sense and/or that I determine with a multimeter. Something like "Pin 2 of this component has to be connected with pin 3 of the other one" If you want to reproduce the board, keep going: * Switch over to the PCB editor and draw the outline (measure with a caliper) * Position all components where they are on the board * Draw traces connecting everything logically correct, probably similarly to the way it is routed on the board. Nothing will change if a trace is 5mm further left or right * If you want, draw the silkscreen accordingly The rest is then the same as with every other board. Export gerber files, order from a PCB manufacturer of your choice


Been there, done that. Engineering is often tedious attention to details.


Preach, brother


Reverse engineer a 4+ layer PCB. Have to multimeter every single pad to every single other pad. BEEEP... U1.23 to R3.2; BEEEP... U1.24 to C101.1 Brings back bad bad memories.


wouldnt exactly call this engineering so much as design work


Depends on what you're after - If you're personally interested in how something works, the process can be as simple as pen, paper, and a multimeter. Look at what's connected where, confirm with measurement, make notes, draw pictures. May be a bit tedious to get a "complete" schematic going, but it's often good enough to get you navigating the general structure of a thing for whatever your purpose may be. Can get pretty messy with multilayer boards. formalize as necessary. If you're interested in something procedural, flying probe manufacturers offer a variety of solutions for "automated reverse engineering". I don't have any practical experience with this, however I imagine there are varied approaches, with none of them being completely turnkey. In short, board goes into machine with probes, machine is instructed where to place probes, machine probes board in a series of ways, machine records what's connected where (perhaps with some sophistication), machine spits out net list, net list gets converted into something more meaningful, human reviews, organizes, makes informed assumptions and then fills in gaps. Some level of rinse and repeat. I'd imagine someone could make a pretty fruitful career diggin' into this stuff. ymmv. Some handwaving: [Reverse engineering for flying probe systems](https://www.seica.com/wp-content/uploads/2019/12/reverse-engineering.pdf)


Use your handy X-Ray microscope on the board with 4 to 12 layers.


Nah, run it through a planer and image again ;)


Hm.. will my Dewalt planer give enough accuracy? Or should I go with Grizzley or Jet?


You tell me - inner copper is usually ~17µm high


Better go with sandpaper


Use a multimeter in continuity mode, we call that “ringing out” your circuit. At least that’s what I learned it as


That’s the plan! Never learned about this in my electrical classes (I studied marine engineering so the furthered we went was transistor analysis) I’m going to figure it out!


You’ll do fine! Identify ground and power nets first, and then you can give the remaining signals a token name. Taking some scans and highlighting connected nets top to bottom helps too, but internal traces are difficult


Maybe we can write a program for this. First input is image of back of pcb. Then it names every node on a image and for second input asking for components that connected each nodes. That would be easier than doing by hand also it can automatically import your scheme to circut analysis softwares.


Label the pads. Create a run list. Draw a schematic. Doing run list allows you to easily see what ground would be.


A meter measuring continuity, a pencil and several big sheets of paper.


That’s how I’m doing it!


And a big eraser


On a semi related note, way back in the day there was (still is?) a company named Sams Photofact. They published schematics of TVs, radios etc. that they determined by painstakingly disassembling products and reverse engineering them.


Yes, use a scanner, some layered photo editor and effort to reverse engineer the schematic.


Just watch any bigclive YouTube videos for examples. He reverses every little thing.


Eyeballs and potentially a DMM. Write down all the components. Then start mapping out each trace.


EEVBlog 675 and 1415 are really good! Playlist that includes these: https://youtube.com/playlist?list=PLvOlSehNtuHvatF_8oJ2qpKxi_wWw6YN4 714 looks good too but I haven’t watched it before.


Looks like a one layer board, so you should he able to easily identify the components and then just follow the for each pin traces. In this case pencil andp paper are the easiest tool. For boards with more layers, the right tool would be a DMM using continuity mode. In a professional environment, you'd just do x-rays of the board but still have to match pins and traces manually.


Yes that is the plan! Thank you!


Multimeter and patience. Or light bulb battery and some wire


¸paper, pencil and some common knowledge!


Thanks. Not sure if it’s common knowledge, especially since I’m not an electrical engineering student. However I do remember circuit analysis from my engineering courses- thanks to all the useful information here, I plan on giving it a try- the pen and paper way


common knowledge only, because... you dont have to know what R12 is, how it works and so on, you just have to know the simbol for it to draw it on the paper... then there is apiece of copper... draw the line (on the paper...) and it is connected to C4... draw the symbol for capacitor and go on... simple as that...


In general and for non-trivial designs, if you want the schematic to be intelligible to humans much less actually serve as useful documentation, it's a manual process. As others pointed out, you usually use a meter on continuity to follow the tracks on the PCB and verify connectivity when you get to a suspected endpoint. Removing all the components from the PCB can help with this by removing sources of uncertainty due to diodes, low resistance paths, accidentally biasing actives, etc. For one- and two-layer designs, it's possible to scan the PCB, apply some image trickery to it to reduce both to a 1-bit image, manually mark any holes that have copper connectivity but aren't plated through, then extract a netlist via automatic means. Then you can convert the netlist to a very messy schematic that's missing component blocks (each node will just be a common point). This won't be very useful for documentation purposes, but it would let you make minor changes, ECO the design back into a layout (which you've also converted from the raster scan to something vaguely usable), make the tweaks, and generate new artwork for fabrication. This is occasionally useful with legacy designs for which the original documentation has been lost but were minor tweaks/fixes are needed.


Thank you! Pen and papering it out now, having a blast with it!


Depends what you have. If you have a working version of the board with components labeled, its just a slow manual process. Even a board like oicture 2 isnt gonna be too bad just time consuming. The less of that you have the worse it gets. A completely empty unlabeled board like you have in picture 1, yes im aware thats the back of the same board but pretend it isnt for a minute, you might be able to make some educated guesses especially if you know what its supposed to do but its not gonna be fun


Bed of nails testing is the best way to do this, but this is a very expensive machine


You gotta watch yourself some Big Clive


Thanks to this post, I found him, subscribed. Awesome and thorough material!


It is all things in that pictures. You just need time to figure out that layout. But there is no firmware for 2051.


The only way I know, is the old-fashioned way---with pencil and paper! That's how "Sam's Photo-Facts" were made, for many decades. They did that for two reasons: 1) so as to not infringe on any copyrights, that would apply to published material, and 2) to avoid repeating any mistakes that might be in such material.


That’s the plan! I’ve never worked with a circuit board before, only bread boards in my electronic classes back in the day! Thank you


Since the board you are holding is single sided, it literally is the schematic. Start there and move to double sided. Multi layer usually requires x-ray imaging, but sometimes you can use a back light to see the inner traces. It is a manual process. Don't expect to find something to do it for you.


Yeah, follow the wires


As has been said before, it would be very tedious. I would go a pencil-and-paper route, where you start with one component, sketch the schematic symbol, and follow the trace from one component lead to another. Repeat enough times with all of the component leads, and you have your rough schematic. Then, you can clean it up in some sort of computer program, if you want to recreate the pcb by having a manufacturer make one for you. If you wanted to make one by hand, there are ways to print a stencil. Edit: a multimeter can be helpful to confirm the continuity between pads that appear to be connected by traces.


A pencil and paper! Just follow the traces and draw it up with symbols for the various components and voila