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Reverse Engineering with Photoshop

Two tricks that work with almost any photo-editing software.
Useful for circuit repairing, circuit bending, circuit understanding.

 

Trick 1: Highlight PCB tracks with different colors for easy identification

 

This 12-keys keypad failed after years of daily use. No schematic or replacement parts from the original manufacturer. The only option was to replace it with an off-the-shelf telephone-style keyboard.

However, I had to discover (by reverse-engineering) the original connector pinout to adapt the new keyboard.

Following the maze of each and every PCB track in a circuit is boring and error-prone, so I looked for an easier way to get the job done.

Here is how I got the picture on the right:

 

Take a picture of the PCB, and feed it through a photo-editing program.

Select the bucket fill tool and choose the color you like to paint the track.

Tip: vivid colors work best

Click on on the track you want to highlight.
It's amazing to see tracks selected instantly, no matter how intricate they are.

Tip: tweak a little with the tool's sensitivity control for best results

An extra benefit is that you can add annotations - and your work is automatically documented for future reference.
Not bad for a 5-minute trick.

With the bucket fill tool you can easily paint each track in a different color

 

 

Trick 2: "Transparentize" the PCB to see connections on both sides

Superman's X-ray eyes: see-through PCB!
Great for circuit bending and repair

 

This techinque takes a bit longer, but it's much better than flipping a board one zillion times to understand how parts connect together.

Here are the steps to get Superman's X-ray eyes (well, sort of):

Take a picture of the PCB board, track side.

Tip: We are going to take two pictures to overlap. Use a tripod and align the board on a fixed reference (e.g. desk edge) for best results

Take a second picture of the board, this time component side.
We are going to overlap the pictures, so try to get them exactly the same size and alignment.

Start your favourite photo-editing software and place the track-side picture on a layer.

 

Add a new layer on top of it, for the parts-side picture

Select the tracks-side layer and mirror it horizontally. This is a very important step!

Set top-layer tranparency to 50% and move the parts-side picture to align perfectly with the tacks-side picture below it.
Holes and corners are good points to check for precise alignment.

Once aligned, restore top-layer tranparency to 0% (that is 100% opacity).

Tip: If not using a tripod, it could be necessary to stretch and rotate the pictures to make them exactly the same size and orientation.

Without leaving the top layer (parts side), select the magic wand tool .
Click on an area free from components. A large portion of the PCB area should get selected.

Tip: tweak a little with the tool's sensitivity control for best results

Erase the selection (press CANC or CTRL-Z on most softwares).
The PCB tracks should appear from the layer below.

Repeat the select/erase process until done!


Web link: a nice reverse-engineering instructable by Nagi Hatoum

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