Tracing a PCB using photo techniques

[R.G.]

I've posted how to do this before, but since I had the occasion to do a bit more of it today, I took the chance to write up a little photo essay on the technique.

It's currently first in the "New at GEOFEX" section, or you can go directly here: http://geofex.com/FX_images/Tracing a PCB.pdf

The trick is to use photo programs to get a picture of the bottom traces imposed over the components. You can do this by taking a high res photo of top and bottom. Then you clean up the photos of extraneous stuff; mirror image the trace side; use your photo program's techniques to isolate just the pattern of traces; place the trace pattern over the components, and then add some tranparency to the traces so you can see the component details where needed.

Done properly, you can then just convert the circuit to a schematic directly, no flipflopping the PCB while scratching your head about where did THAT go?

[petemoore]

 Tricky ! Slick too.
  Remember to set the probe down before scratching your head.
   I thought you've already had your head sufficiently scratched with probes by now anyway...well better late than never, there's still some circuits out there that haven't been scratched.

[Steve Mavronis]

Cool way to do it more directly than I have done. I've been using a transparent layer in a graphics program with a grid to measure where things should go in a PCB editor.

[R.G.]

Cool way to do it more directly than I have done. I've been using a transparent layer in a graphics program with a grid to measure where things should go in a PCB editor.

Do you put the traces in and then mirror the traces layer to get a top side view?

[joegagan]

i have used this technique as well. usually, just putting the 'mirror' trace photo right alongside the component side photo works for what i am trying to do.

also, don't forget, you can use the contrast and brightness settings to bring out invisible things in photos - as in this ebay photo of the bottom of a wah, the flash washed out the serial number unitl i tweaked the photo in GIMP

[Gurner]

I've never used the technique, but thought I'd chime in - it's probably worth underlining that when taking a photo of the board I reckon you should try to take it exactly over the centre of the board (ie looking down on the centre - with equal distance in the viewfindr around the edges)...this is to avoid parallax errors., becuase hen when you 'crop' to the board edge in a photo editing tool, you can then tell the software what dimension/size the photo is (ie the board).....your printout should then be pretty accurate scale wise.

Also use top lighting (such as the flash on the camera - or just 'off camera if the board is particularly reflective - else stong shadows may impede your overall 'tracing' alignment progess.

Also if you don't want an exact replica with respect to curvy track/lines, then use a polygon tool - it follows your mouse clicks but in straight lines (more pcb track-esque vs hand drawn)

[Galego]

I've used it, while trying to figure out the layout of the Boss HM-2. Big headache.

[space_ryerson]

I've had some luck using this technique. I've found in Photoshop that once I've cropped the photos somewhat and get the inverted PCB side on it's own layer, using Edit>Transform>Distort (don't forget to unlock the layer!) can correct any slight perspective from not taking the photo 100% dead on, and makes the parts line up better with the PCB. I hope I'm explaining that right.

[Steve Mavronis]

Cool way to do it more directly than I have done. I've been using a transparent layer in a graphics program with a grid to measure where things should go in a PCB editor.

Do you put the traces in and then mirror the traces layer to get a top side view?

On the couple pedals I've "psuedo-traced" I worked from the top component side so the traces are reversed. I didn't actually trace anything. Instead I used a grid overlay just to help measure the spacing and re-drew the PCB pattern. It's probably the hard way to do it but as a long time artist since childhood if I can draw faces and stuff "by eye only" (see my Facebook artwork album for some samples - http://www.facebook.com/album.php?aid=2009395&id=1172726570&l=efbc0d285d) I am just used to it I suppose. I will try the method you suggested though.

[R.G.]

I use Corel's graphics setup. It has a masking feature that will mask based on color or a range of colors. That will get the traces separated in many cases.

However, for the example, I found it was faster to just use an eraser tool and erase the photo of the traces side to white over all the pads and traces. This is too tedious for a more complex board, though.

[Steve Mavronis]

I want to start cataloging classic basic stompbox circuit board layouts like the old DOD 250 Overdrive, MXR Distortion+, and Ross Distortion. I know they have been done before but there is a satisfaction doing it yourself. What I'll do is load the PCB image in GIMP as a background layer and use the transform tool to square it up to remove as much distortion as possible. It helps to know the actual board dimensions to do it to scale if you don't have the real thing to measure yourself. I will add a transparent layer on top of this corrected background image of the PCB and draw over it as accurately as possible. Afterwards the finished illustration can easily be flipped to get the other side too. I don't think the color contrast selection method to capture trace patterns will be totally practical if there are components or pots partially obscuring the view.  For me all this is just for study of the original layout in case I choose to reverse engineer my own layout arrangement based on it. I doubt if I'd etch an exact copy of the original board unless it was for a repair replacement like for my damaged pre-LED MXR Distortion+ with some traces fried off the board for example.

[valdiorn]

I've never used the technique, but thought I'd chime in - it's probably worth underlining that when taking a photo of the board I reckon you should try to take it exactly over the centre of the board

Another thing that will affect the perspective is the lens you use. I suggest using the longest focal length available (most zoom), that way you can get an almost anamorphic top-down view of the board.