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**STEP n°4:** assemble Ohmpi
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| | .. image:: step_n_4/step_4_1.jpg |
| 1 +------------------------------------------------------------+
| |Cut 4 ribbon cables composed of 16 wires each to the proper |
| |length (about 1.5m). Each wire corresponds to an electrode. |
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| | .. image:: step_n_4/step_4_2.jpg |
| 2 +------------------------------------------------------------+
| |Crimp the ribbon cable on the corresponding idc connector |
| |with a suitable clamp. Pay attention to the direction of the|
| |cables. Unbalanced IDC connector. The ribbon cable must be |
| |perpendicular to the connector. |
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| | .. image:: step_n_4/step_4_3.jpg |
| 3 +------------------------------------------------------------+
| |Example of IDC connector mounting. The wires should run as |
| |perpendicular as possible to the IDC connector. |
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| | .. image:: step_n_4/step_4_4.jpg |
| 4 +------------------------------------------------------------+
| |Same for a 6 wires ribbon cable of 1 m length. |
| | |
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| | .. image:: step_n_4/step_4_5.jpg |
| 5 +------------------------------------------------------------+
| |Cut the ribbon cable flush with the IDC connector. |
| | |
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| | .. image:: step_n_4/step_4_6.jpg |
| 6 +------------------------------------------------------------+
| |Position 9 spacers above the MUX board, and 9 spacers below.|
| | |
+ +------------------------------------------------------------+
| | .. image:: step_n_4/step_4_7.jpg |
| +------------------------------------------------------------+
| |Profile view for mounting the spacers above and below. |
| | |
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| | .. image:: step_n_4/step_4_8.jpg |
| 7 +------------------------------------------------------------+
| |Cut a 50 cm long wire of any color (here yellow). Strip and |
| |tin each end of the wire. Install the wire "A" on the screw |
| |terminal of MUX board « A ». |
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| | .. image:: step_n_4/step_4_9.jpg |
| 8 +------------------------------------------------------------+
| |Cut a red wire and a black wire of 50 cm length. Strip, tin |
| |and position the wires on the left screw terminal as shown |
| |in the picture: i)Red wire 12 V, ii) Black wire GND |
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| | .. image:: step_n_4/step_4_10.jpg |
| 9 +------------------------------------------------------------+
| |Mount the 4 ribbon cables (16-wires each) with IDC |
| |connectors. A small noise is often heard when the IDC |
| |connector is clipped in place. |
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| | .. image:: step_n_4/step_4_11.jpg |
| 10+------------------------------------------------------------+
| |Mount the ribbon cables with 6-wires with the corresponding |
| |IDC connectors |
| | |
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| | .. image:: step_n_4/step_4_12.jpg |
| 11+------------------------------------------------------------+
| |Cut a red wire and a black wire of 10 cm length. Strip and |
| |tin the wires at the ends. Mount the red wire on the 12V |
| |input and the black wire on the GND input on the right screw|
| |terminal. |
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| | .. image:: step_n_4/step_4_13.jpg |
| 12+------------------------------------------------------------+
| |Mount and fix the second MUX board "B" on the first with |
| |the help of 9 spacers. |
| | |
| | |
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| | .. image:: step_n_4/step_4_14.jpg |
| 13+------------------------------------------------------------+
| |Cut, strip and tin a red wire and a black wire of 10 cm |
| |length. Mount the wires on the left screw terminal. |
| |Red wire 12V input, black wire GND input. |
| |Connect the red and black wires from board A to the right |
| |screw terminal of board B. Red wire 12V input. Black wire |
| |GND input. |
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| | .. image:: step_n_4/step_4_15.jpg |
| 14+------------------------------------------------------------+
| |Crimp a 16 wires IDC connector on the ribbon cable at about |
| |15 cm from the previous connector. Please, pay attention to |
| |the direction of the cable before the crimp procedure. |
| |Mount the ribbon cable on the IDC connector on the board. |
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| | .. image:: step_n_4/step_4_16.jpg |
| 15+------------------------------------------------------------+
| |Repeat the operation for the other 3 ribbon cables. |
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| | .. image:: step_n_4/step_4_17.jpg |
| 16+------------------------------------------------------------+
| |Repeat the operation for the 6 wires ribbon cable. |
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| | .. image:: step_n_4/step_4_18.jpg |
| 17+------------------------------------------------------------+
| |Cut a 50 cm long wire "here purple" (Color not relevant but |
| |to be defined). Strip and tin the wire at its ends. Position|
| |the wire on the input B of the screw terminal of the |
| |multiplexing board B. |
+--------+------------------------------------------------------------+
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| | .. image:: step_n_4/step_4_19.jpg |
| 18+------------------------------------------------------------+
| |Repeat all these operations for the third MUX board |
| |called "M". |
+--------+------------------------------------------------------------+
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| | .. image:: step_n_4/step_4_20.jpg |
| 19+------------------------------------------------------------+
| |Repeat the operations for the fourth MUX Boards. Attention, |
| |it is necessary to position 5 different spacers (here nylon |
| |screw hex spacers) in between the “M” board and the “N” MUX |
| |Board (as shown on the photograph). Refer to the following |
| |photographs for more details on the assembly of the spacers.|
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| | .. image:: step_n_4/step_4_21.jpg |
| 20+------------------------------------------------------------+
| |When mounting the 4th MUX board ("N"), screws can be placed |
| |on the nylon spacers to fix the boards together. Note that |
| |the other spacers could be used for this purpose. |
| |Connect ribbon cables (16 wires) from board 3 to board 4 as |
| |previously described. Connect the red wire (12V) of MUX |
| |board "M" to the 12V terminal of the right screw terminal |
| |of MUX Board "N". Connect the black wire (GND) of MUX board |
| |“M” to the GND screw terminal on MUX board “N”. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_22.jpg |
| 21+------------------------------------------------------------+
| |Cut a red wire and a black wire of one meter length. Place |
| |the red wire on terminal “12V” and the black wire on |
| |terminal “GND” of the left screw terminal. Tie the wires |
| |together. |
+--------+------------------------------------------------------------+
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| | .. image:: step_n_4/step_4_23.jpg |
| 22+------------------------------------------------------------+
| |Tie the A, B, M and N wires together |
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| | .. image:: step_n_4/step_4_24.jpg |
| 23+------------------------------------------------------------+
| |Cut a PVC plate with the following minimum dimensions : |
| |200 mm * 150 mm * 5 mm |
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| | .. image:: step_n_4/step_4_25.jpg |
| 24+------------------------------------------------------------+
| |Drill the plate to mount it on the remaining metal spacers. |
| |Do not tighten the assembly. |
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| | .. image:: step_n_4/step_4_26.jpg |
| 25+------------------------------------------------------------+
| |Position the Raspberry Pi (RPI) board on the plate so that |
| |you can access the USB ports. Mark the holes of the RPI |
| |board on the plate for mounting. |
+--------+------------------------------------------------------------+
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| | .. image:: step_n_4/step_4_27.jpg |
| 26+------------------------------------------------------------+
| |Add spacers on the PVC plate. |
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| | .. image:: step_n_4/step_4_28.jpg |
| 27+------------------------------------------------------------+
| |Attach the PVC plate to the metal spacers with washers |
| |and nuts. |
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| | .. image:: step_n_4/step_4_29.jpg |
| 28+------------------------------------------------------------+
| |Position and fix the RPI card on the spacers |
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| | .. image:: step_n_4/step_4_30.jpg |
| 29+------------------------------------------------------------+
| |Add spacers on the RPI board. The red (12V) and black (GND) |
| |wires coming out of the "M" MUX board must pass under |
| |the RPI board. |
+--------+------------------------------------------------------------+
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| | .. image:: step_n_4/step_4_31.jpg |
| 30+------------------------------------------------------------+
| |Place the measurement board on the RPI GPIO outputs and on |
| |the pre-positioned spacers. Note that LEDs are present on |
| |this measurement board with an associated resistance simply |
| |for testing purposes (do not consider this temporary |
| |modification of the board). Same for the orange wire present|
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+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_32.jpg |
| 31+------------------------------------------------------------+
| |Connect the wires " A " (here yellow), " B " (here purple), |
| |" M " (here brown) and " N " (here blue) on the |
| |corresponding terminal blocks on the measurement board. |
| |Connect the 6 wires ribbon cable on the measurement board |
| |by passing under the PVC plate.Connect the red and black |
| |wires to the 12 V and GND terminal block. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_33.jpg |
| 32+------------------------------------------------------------+
| |Top view of the assembly. Add clips to secure the wires |
| |together. |
+--------+------------------------------------------------------------+
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| | .. image:: step_n_4/step_4_34.jpg |
| 33+------------------------------------------------------------+
| |Second view. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_35.jpg |
| 34+------------------------------------------------------------+
| |Zoom in on the connection of the M and N wires. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_36.jpg |
| 35+------------------------------------------------------------+
| |Zoom in on the connection of the A and B wires. |
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_37.jpg |
| 36+------------------------------------------------------------+
| |Zoom in on the connection of the « 12V » and « GND » wires. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_38.jpg |
| 37+------------------------------------------------------------+
| |Fixing the measurement board on the spacers present on the |
| |RPI board. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_39.jpg |
| 38+------------------------------------------------------------+
| |Place the SD card containing the OS and the pre-installed |
| |programs. Connect a mouse and a keyboard to the USB inputs |
| |of the RPI board. Connect a monitor to the HDMI output of |
| |the RPI board. |
+--------+------------------------------------------------------------+
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+--------+------------------------------------------------------------+
| | .. image:: step_n_4/step_4_40.jpg |
| 39+------------------------------------------------------------+
| |Connect the red and black cables of board A to a 12V battery|
| |or other laboratory power supply delivering a 12V-DC |
| |voltage. |
| |Enjoy 😊 |
+--------+------------------------------------------------------------+