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--- projects:3dprinting:anycubic_i3_mega:redesign_hub_pcb [2020/11/09 00:58] – [Redesign of the Mega Hub PCB] admin
+++ projects:3dprinting:anycubic_i3_mega:redesign_hub_pcb [2022/07/12 13:31] (current) – [Wiring the new circuit boards - internally] admin
@@ Line 27: / Line 27: @@
 ===== Redesign of the Mega Hub PCB =====
-Within a period of one year, the circuit board evolved into the current design((The three earlier [[projects:3dprinting:anycubic_i3_mega:redesign_hub_pcb_v1_v2_v3|iterations are described here]].
+Within a period of one year, the circuit board evolved into the current design((The three [[projects:3dprinting:anycubic_i3_mega:redesign_hub_pcb_v1_v2_v3|predecessors are described here]].
 )) which has the following features:
   * ESD-protection on all pins which are connected to the controller.
@@ Line 37: / Line 37: @@
 |  //Top//  |  //Bottom//  |
-The ESD-protection is an absolute necessary requirement for everyone who is experimenting with changing external hardware. Without protection, the risk of ESD damage is high due to the fact that the original temperature input is wired unprotected to the controller.((This can easy happen to the heatbed temperature sensor, connected to the Atmega2560, Pin 83 (Analog 14), with an external pull-up resistor of only 4k7.))
+The ESD-protection is an absolute necessary requirement for everyone who is experimenting with changing external hardware. Without protection, the risk of ESD damage is high due to the fact that for example the original temperature input from the heatbed is wired unprotected to the controller.((The heatbed temperature sensor is connected to the Atmega2560, Pin 83 (Analog 14), with an external pull-up resistor of only 4k7.))
 The new circuit board fits at the original location. The breaking-off circuit board (using so-called mouse-bites) is meant to be located at the other side of the printer and provides connections for the X-stepper, Z-stepper-Left and accordingly endswitches.
-The reason that the original external dual row 2mm connectors were abandoned is that these are neither very robust, nor do they offer much flexibility in respect to upgrading/changing the printer.
+{{ :projects:3dprinting:anycubic_i3_mega:img_20201109_234033b.jpg?direct&400 |}}
+The reason that the original external dual row 2mm connectors were abandoned is that these are neither very robust, nor do they offer much flexibility in regard to upgrades/changes.
 The schematic diagram and pinout of the board can be downloaded from here:
@@ Line 47: / Line 49: @@
   * {{ :projects:3dprinting:anycubic_i3_mega:i3_mega_hub4-pinout.pdf|Pinout / Pin description of the connectors at the circuit board.}}
-To housing need to be slightly modified for the D-sub connectors. For details, [[projects:3dprinting:anycubic_i3_mega:new_hub_pcb_mechanical|see this page.]]
+The housing needs to be slightly modified for the D-sub connectors. For details, [[projects:3dprinting:anycubic_i3_mega:new_hub_pcb_mechanical|see this page.]]
-===== Cutting holes =====
+===== Wiring the new circuit boards - internally =====
-For cutting the holes in the metal casing, the following file can be helpful:
+To understand how the wiring needs to be modified, please look at the following diagram. It shows how the protection works in principle:
-  * {{ :projects:3dprinting:anycubic_i3_mega:i3_mega_hub2-outline.pdf|I3 MEGA HUB2 outline.}}
-This file contains the following drawing:
+{{  :projects:3dprinting:anycubic_i3_mega:esd_principle2.png?direct&500  |}}
-{{ :projects:3dprinting:anycubic_i3_mega:i3_mega_hub2-outline.png?direct&600 | Drawing to facilitate positioning of holes.}}
-To start, first unscrew/remove everything which is attached or mounted on the main metal casing. It is better to prevent any metal dust getting onto the circuit board and/or power supply or anything else. When done, for the large cutout, draw with a pencil horizontal and vertical lines on the metal casing, using the position of the press-in nut, which is visible from the outside, like shown on the picture below:
-{{ :projects:3dprinting:anycubic_i3_mega:img_20191116_102336s.jpg?direct&400 |}}
-Then place the printed drawing with some double sided sticky tape on the metal casing, using the drawn lines as guides:
-{{ :projects:3dprinting:anycubic_i3_mega:img_20191116_103258s.jpg?direct&600 |}}
-Using the printed drawing, do the following:
-  * Use a punch tool to mark the centre of the two holes (here visible on the right) for mounting the pcb. These need to be drilled to 3.0 mm.
-  * Use a sharp knife to draw lines, which mark the shape of the metal cut-out as can be seen below.
-First drill the two 3.0 mm holes and counter-sink them. Then drill with a larger diameter several holes to roughly cut out the major part of the metal. Finally use a file to complete the cutout. The result should look like this:
-{{ :projects:3dprinting:anycubic_i3_mega:img_20191203_005326s.jpg?direct&600 |}}
-For the other side of the metal casing, the positioning is much easier, since we do not need to take into account any existing mounting points. Therefore place the drawing from above roughly as shown in the image below:
-{{ :projects:3dprinting:anycubic_i3_mega:img_20191116_100327_hdrs.jpg?direct&600 |}}
-First drill the 4 holes on each side and counter-sink them. Continue with cutting with a sharp knife some lines of the cutout in the metal casing. Then use a drill to cut out the majority of the metal and use a file to finish the rectangular shape.
-The result should look like the following:
-{{ :projects:3dprinting:anycubic_i3_mega:img_20191203_005102s.jpg?direct&600 |}}
-===== Mounting circuit boards =====
-Mount the large circuit board using the following spacers:
-  * 4x 2.5mm for additional distance at the 4 existing press-in nuts.
-  * 2x 6.0mm for the 2 mounting points at the right.
-With some heat shrink and glue the 2.5mm spacers can be added more permanently to the existing press-in nuts, preventing them from falling off when trying to mount the circuit board.
-The small circuit board needs 4x 6.0mm spacers for mounting.
-From the inside the circuit boards should look like the following:
-^  Main HUB  ^  X-stepper/Z-stepper-L  ^
-|  {{:projects:3dprinting:anycubic_i3_mega:img_20191208_162432.jpg?direct&200|Main HUB}}  |  {{:projects:3dprinting:anycubic_i3_mega:img_20191208_115325.jpg?direct&200|X-stepper/Z-stepper-L}}  |
-===== Wiring the new circuit boards - internally =====
-Internally the following cables need to be made:
-  * todo.
+The most important connection point for ground is realized using a [[https://www.we-online.com/katalog/datasheet/7461096.pdf|Würth REDCUBE PRESS-FIT T-Block]] (Art. Nr. 7461096), which has M4 thread and can be used to establish a connection with very low impedance. No negative or ground wire shall be routed directly between the power supply and the controller circuit board. Instead, all these wires need first to go the T-Block and from there to the controller.
 ===== Wiring the new circuit boards - externally =====
-The following parts have been acquired. Supplier was Farnell (Develektro)
+The following parts have been acquired. Supplier was Farnell:
 ^ Position ^ Part ^ Manufacturer ^ Manufacturer code ^ Farnell ^ Description ^
 | 1 | D-sub Connector Backshell | MH CONNECTORS LTD. | MHDVSL9-K | 2532964 | DMHDVSL Series Zinc Angled |
 | 2 | D-sub Connector Backshell | MH CONNECTORS LTD. | MHDVSL25-K | 2532963 | DMHDVSL Series Zinc Angled |

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