One of the things that I enjoy doing is taking a small one or two sided circuit board and creating a schematic of it. Today I have a circuit board from a 105 db piezo siren for which I am going to create a schematic. Here is the Module.
The first step is to get some paper and choose a starting point. In this case I picked the output transformer and then worked my way back. As you can imagine the board must be flipped back and forth and ones perspective must constantly shift from topside to mirror image and back. The resistors must be read and measured if they can not be seen. This is also done with the capacitors. On this board the identification of the small green mylars were face to face and so one had to be removed to determine the value. When the rough draft of the schematic is finished it is never very pretty. Here is my rough draft.
This is obviously not very good or very clear. In order to not put too many line on this draft the ground line was replaced with ground symbols and one junction point was labeled #3 and a second junction point was labeled *. What happened to #1 and #2? I am not sure it just seemed ok at the time to call them * and #3. After the rough draft is finished I use it to produce a more conventional looking hand done draft. Here is what it looks like after it has been cleaned up.
This one while still not very neat at least looks more conventional and at this point I also add component numbering. I also take close up photos of the board and label the components to match the schematic. This serves to tie things together and to make certain that I have not left anything out of my schematic. Here are the pictures and labels that correspond to the schematic.
Now I take all the drafts and produce a CAD drawing of the schematic to complete my file on this particular circuit.
This process is good exercise for the brain and gives me a very good understanding of the circuit by the time I have finished.
John
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