Component-level Reverse Engineering Techniques?

[DigiTan]

It's pretty easy to go to a search engine or corner bookstore and find a ton of material on engineering at the component level. I've never seen any on basic reverse-engineering though.

Mainly what I'm looking for are methods for taking the PCB of an existing device, and deriving a schematic from the board. Like when you normally design a circuitboard: you do the schematic first, then you have the ratsnest to help you piece together your circuitboard, then you draw the traces. What I want to do is just that, but in reverse order. Are there any good web sites or books on doing that stuff?

 

[Nigel Goodwin]

You're not going to find any easy way of doing it, basically you sit down with a big piece of paper and start drawing the circuit out - it's a difficult job, and takes a considerable time (and often many sheets of paper).

One helpful tool is a bright light source, that can shine through the PCB so you can see the traces from the component side - another advantage is knowledge and experience, so you know what sort of configurations you might be getting.

 

[Hero999]

You can quickly figure out small circuits but you normally don't learn much.

 

[Fred.Amoson]

Use a 2 step process

1. Identify all components and draw them out
2. Using an ohm meter, find what is connected where until everything is done.

 

[jpanhalt]

Some additional things I have used:

1) Photocopying the PCB -- not really as helpful as it may seem to be, but it gives you a place to write things down and allows easy mirroring. If you don't have a program to do that, you can put oil on the paper to get the mirror image.

2) Several colored markers to trace, like VCC, GND, a particular signal. I generally get by with 3 or 4 colors (red, black, green, blue). Those colors show up well on the PCB traces.

3) At some point, I find I need to remove at least some of the components.

I have only had success with old designs. Newer designs are often based on microcontrollers.

John

 

[em2006]

Based on visual check and photocopies (normal, mirrored, resized, etc.), I draw the PCB in vectorial format using a PCB layout tool (a part of a full line design and simulation tools) - placing the component footprints and routing the board manually, exploiting the software facilities. Then I draw schematic diagram and I see if the configuration of the circuit is correct. If the topology is new for me, I try to understand how it work.