how can i reverse engineer the schematics of this simple computer mouse

Discussion in 'General Electronics Chat' started by Adel Beitvashahi, Jun 30, 2017.

  1. Adel Beitvashahi

    Thread Starter New Member

    Jun 30, 2017
    hey i'm new to electronics and i'm working on making a drawing pen out of this mouse so I need to desolder all the parts out of the pcb and put them together in a way so that they can fit in a relatively thin pen for drawing, my problem is i dont know how each part is connected, i have looked online and couldnt find a schematic for the mouse product. its a mini ihome mouse

    are the dark green lines wire connections or the light green parts?

    here are some pics

    yellow - Copy.jpg green - Copy.jpg
  2. WBahn


    Mar 31, 2012
    The light green is the copper. Consider that the copper has to connect the pins that are soldered into the board, so the regions surrounding each pin have to be copper.

    I suspect you'll find getting it into a workable pen is going to be much easier said than done, but good luck.
    Adel Beitvashahi likes this.
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    Man, you have a long road ahead.

    The light green are the PCB tracks.
  4. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
    Crash course:
    A single sided when it's made has a bunch of holes and a silk screen (part designations) on the top layer.
    The bottom layer at one point was solid copper. A UV resist was applied, developed and exposed and the copper etched.

    You were left with tracks and exposed copper areas. Making the board mostly copper is less wastefull.
    SOLDER resist is applied which is usually green that covers the entire PCB except the pads.
    So, your seeing the contrast of the board and copper traces.

    One processes used for the pads (where components are soldered) is HASL. This is where a layer of solder is applied at leveled with hot air, hence Hot Air Level Solder.

    Now, the board can be drilled.

    This is just a quick overview for the board I see. A single sided PCB. it gets a lot more complicated.
  5. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Looks like you have removed the 8 pin dil chip and 4 pin lens, you can see the Sda and Slc wires to the usb, the other two are +/-5v, the other 4pins on the chip will be for left right buttons and up/down wheel clocking,.. So you're best solution is to look for mouse circuits using the same chip number.
    Last edited: Jul 1, 2017
  6. atferrari

    AAC Fanatic!

    Jan 6, 2004
    The visual recognition is of help, BUT and it is an important but, measuring continuity is the way to identify connections with not even seeing the actual copper trace.

    My suggestion: Identify always first the common rail. Then the power rail.

    Once there, go to connectors and try to identify whatever could be considered input or output.

    Use in the beginning a huge sheet of paper where your schematic mimics the physical layout of the actual PCB.

    Once you think you are done, check the circuit with power on. Be aware that the circuit could be out of order.

    Buena suerte.
    cmartinez likes this.
  7. Adel Beitvashahi

    Thread Starter New Member

    Jun 30, 2017
    so since its a single sided pcb, can i assume that everything on the same block of light green (copper block) is to be connected to each other in no specific order?
  8. atferrari

    AAC Fanatic!

    Jan 6, 2004
    Instead of assuming, go and check it!

    Have you read my post?
  9. be80be

    AAC Fanatic!

    Jul 5, 2008
    Last edited: Jul 1, 2017
    absf likes this.
  10. RichardO

    Late Member

    May 4, 2013
    Wow! Great link. It looks like it gives everything but what the designer had for breakfast. :D
  11. Adel Beitvashahi

    Thread Starter New Member

    Jun 30, 2017
    thank you everyone for the answers. I just went over the pictures and drew some links between the pins which were in the same copper block.
    gonna crop the parts out and connect their pins to make it like a proper schematic and test it on breadboard
  12. Adel Beitvashahi

    Thread Starter New Member

    Jun 30, 2017
    busy week. just took out all the parts and soldered some wires to them so i can mount them on breadboard.

    here is what i thought were the connected parts and the other two pics for reference. (the pic on the left is horizontally flipped btw, so originally the green switch is on the left side)

    two questions:
    the two cyan pins in the middle picture are from the mouse switches and it looks like they are connected to nothing, does that mean they are grounded?
    i'm trying to connect all the parts on the breadboard but i'm not sure how to connect those two to ground, can i just connect them to nothing and call it a day?
    thank you very much for helping me!
  13. Adel Beitvashahi

    Thread Starter New Member

    Jun 30, 2017
    update: nvm those questions above. it works on breadboard. the grounds dont need to be connected to anything.
    Last edited: Jul 7, 2017
  14. Ford Prefect

    Senior Member

    Jun 14, 2010
    Looking at the circuit board.
    It looks like the cyan dots are merely anchor points for the buttons (which are shown in black)
    ...and the red solder points are terminals / anchor points
    Adel Beitvashahi likes this.