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E-11 Doopydoos with Sound & Light building thread


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The Inner bolt : 


At the local hardware store I bought a piece of drain pipe which has approx. the same diameter as the doopydoos pipe.

I made a piece that fits the hole. This piece will be the cover of the hole of the inner bolt.

The able to positioning the Charging handle I used the same material as the end of the inner bolt.



On the drain pipe I added a strip of metal to give it the authentic look.



As I read in the reference guide, the charging handle can easily be broken off. So I used a large nail inside the handle to give it some strength.



The complete set looks like the picture below. (Of course it needs a paintjob)









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After describing all the subsystems it's time to combine it all.

Beneath are the schematics of the electrical circuits.  To keep everything "readable" I split each function into a separate sheet.

1) Data channels of the Arduino.

      There is a TXD/RXD-line towards the WT2000M02 player. 

      To detect if the MP3-player is still busy the "BUSY"-line is used.

      The control of the OLED is done by the SDA/SCL port on the arduino (A4/A5)

2) Sound control

      Electrical connections from WT2000MO2 to 3W amplifier and speakers

3) Voltage supply of LED's and amplifier.

      As the amplifier needs 5V I added a buck converter (DC-DC Step down module : SG125-SZ) between the 9V-battery and the Amplifier.  A buck converter is able to lower the                voltage without much power consumption.

4) Triggerfunction

      A pull-down resistor is added to the trigger to create 0V or 5V when the trigger is pulled.

5) LED-control

     Not much to tell here. (At the latest moment I added 5 pull-up resistors to this circuit. This way the LED's are not lit when the blaster is starting up).

6) Rotary function

     Same as the triggerfunction. There are 4 pull-down resistors used.

7) Voltage supply arduino/OLED and MP3-module

     As the arduino module is able to convert 9V into 5V there is no need to add a buck converter here. 

Dia2.JPG.efa37e2c18a27c1d7fcef4cf2e7f8f01.JPGDia3.JPG.9b2c421435b5f4fc341b46372cfc1373.JPGDia4.JPG.496f1a1bd31af1b3b6d68979aac7fcfe.JPGDia5.JPG.5e6408a2a2874c876a2e5520bbf4d798.JPGDia6.JPG.7e7f51e027bc3e573dde5e3334756a31.JPGDia7.JPG.0fef8597db940425d7d3eff2b9e048b9.JPG sheet.



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The schematics above look simple, but when it's all combined it looks like spaghetti (without the meat-balls :D).

To be able to miniaturise this I made a layout of my resistors, pins and needed wires.



After validating this schematic I made this in real life by soldering the resistors on a circuit board and adding sockets where I can place the MP3-player and Arduino-board.

I used sockets so I don't have to solder the arduino and player directly to the circuit board.

(Luckily I did this, because I blow up a the SDL/SCL gates during testing. I only needed to replace the arduino without soldering the circuit board again.




To save space for all the wires I removed all non-used pins of the MP3-player and Arduino.



<Open heart surgery in progress>  



Another benefit of using sockets is the fact there is room to solder the wires;)



When everything is soldered I added the boards and put in the gap I created earlier.



Edited by Xinx
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The buck converter is placed underneath the charging handle so it won't be visible.




After glueing the ammoclip, innerbolt and charging handle onto the blaster the project is finished.





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Having read the whole thread now I can offer some possible assistance to future attempts at this.

Arduinos have a resistor that you can optionally enable on each pin using INPUT_PULLUP mode. This has the side effect of reversing the reading the pins but means you don’t need an external pull up/down resistor which can save a lot of space in small space builds like this. The only note is you don’t want much draw in the line or it will blow the resister in the CPU module.

The feature is documented here : https://www.arduino.cc/en/Tutorial/DigitalPins

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