Mendel Electronic Wiring

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Mendel Build Documentation



Introduction

This page describes how to wire up RepRap Version II "Mendel". Before you wire the machine up, test the circuit boards individually as described on this page.

Wiring-diagram.png

This is the overall Mendel wiring diagram; click the image for a full-resolution version. The wiring diagram is stored as an [Eagle] schematic in your download at mendel/electronice/mendel-wiring-diagram.sch. The latest version is in the [RepRap subversion repository here], but that may be an unstable version in development. In the diagram above multi-way connections are shown as thick lines with a number next to them. The number is the number of wires in the connection. Numbers in brackets are the lengths of the wires in centimeters. Thin wires are single wires.

One Mendel will need:

  • A RepRap Motherboard,
  • A Mendel USB and power connector,
  • 3 RepRap Stepper drivers,
  • 3 RepRap Opto Endstops, and
  • As many RepRap extruder controllers as you have extruders.

For details on the individual printed circuit boards and how to build or adapt them, follow this link.

The power wiring is not shown on the diagram for clarity, but it is very simple. The 12 volts from the Mendel USB and power connector is connected in parallel to the three stepper driver boards and to all the extruder controller boards. The Motherboard does not need to be connected to Mendel's internal power connectors. It is powered by the USB connection from the computer. The green (RTS) side of the USB<_>TTL cable goes to the top of the Motherboard, and the black (GND) side goes to the bottom.

The extruders are connected in parallel to the RS485 and to the SDA and SCL ports on the Motherboard. The system only has four connectors for these on the Motherboard, but you can chain these together up to any reasonable number (in theory it should be possible to drive 64 extruders at once...).


Power Cabling

Start by wiring up the 12-volt power cables. You'll need 1.1 m of twin wires.

The standard RepRap 12v power connector is a 3-pin XLR connector.

XLR-connector.png

The picture immediately above is looking into the socket (female) and at the pins (male). Pin 1 is the ground (negative) connection and pin 2 is +12v connection. Pin 3 is not used. Mendel has a panel-mounted male plug connector.

Use wires of different colours that are capable of taking 8 amps. If your wires are not twisted or paired you can easily twist them up yourself by putting one end of the pair in a vice, the other end in a hand twist-drill chuck, and winding. Do all the wire at once, then cut it.

Chock-block.jpg

Attach a four-way "chocolate-block" connector beside the XLR power input. You may need to drill a couple of extra 3mm holes in the stepper-plate, depending on the hole-gaps in your connector.


Xlr-power-mendel-plug.jpg

Solder two short wires to the XLR power connector as shown. Measure them to the two central connections in the chocolate-block. Then untwist them, put heatshrink on the terminals, and twist them up again. Make two small U-shaped pieces of wire to attach the two central chocolate-block connectors to the two outside ones. Put all the wires in the block, but don't tighten the screws yet.


Stepper Cabling

Stepper-power.jpg

Chain the stepper driver boards' power connections together back to the chocolate-block.


Extruder Cabling

Extruder-power-taped.jpg

Run wires up the leg to the extruder board as shown.


Finishing the power wiring and testing

Tighten all the screw connectors. Tug each wire with long-nosed pliers to make sure it is securely connected.

Use a continuity tester to make sure that:

  1. The power is getting to each board,
  2. The two power lines are not shorted, and
  3. The polarity on each board is correct.

Wiring Video

The following video shows the runs of all the wires:

<videoflash type="vimeo">8397407|640|480</videoflash>