Opto Isolator v1.0

Overview

The Opto Isolator board allows you to pass signals between two circuits without having to connect them electrically. They are great for eliminating noise problems, or to connect circuits that have different voltages. In the RepRap system, they allow us to isolate the noisy motor driving circuits from the rest of the electronics. This makes it easy to do advanced things like use interrupt driven rotary encoders, etc.

• You'll need a soldering toolkit to do most of this.
• Read our Electronics Fabrication Guide if you're new.

Get It!

Full Kit

• Buy the full kit (components + PCB) from the RRRF

Raw Components

• Buy this PCB from the RRRF
• Buy the components with ease w/ parts.reprap.org

Files

You can download the electronics files from Sourceforge.

This file contains the following:

• GERBER files for getting it manufactured
• PDF files of the schematic, copper layers, and silkscreen
• Eagle source files for modification
• 3D rendered image as well as POVRay scene file
• exerciser code to test your board.

Schematic

Interface

The opto isolator isolates 2 circuits electronically by sending data as light. It has 2 separate VCC and 2 separate Ground connections.

With IDC cables, the red pin generally denotes pin 1. The pins are counted up from that pin until reaching the other side of the cable.

IN

This is the side that is sending data.

OUT

This is the side that is receiving data.

Build It

Watch the video

Opto Isolator v1.0 Timelapse from Zach 'Iowa' Hoeken on Vimeo.

Board Bugs

• No bugs yet, please report any you find to the forums.

Printed Circuit Board

You can either buy this PCB from the RepRap Research Foundation, or you can make your own. The image above shows the professionally manufactured PCB ready for soldering.

Components

Soldering Instructions

Socket

The socket will hold both chips. Make sure the semi-circle lines up with the mark on the silkscreen.

220 Ohm Resistors

Fold the wire over close to the body and insert it into the PCB. Make sure the wire faces the chip socket.

3.3K Ohm Resistors

Fold the wire over close to the body and insert it into the PCB. Make sure the wire faces the chip socket.

C1-C4

Ceramic capacitors can be inserted in any direction.

IDC Headers

Insert the headers and solder them. Make sure you put the notches facing inwards so that they line up with the silkscreen.

Insert Chips

There are 2 chips to insert. Insert one at the very top, and one at the very bottom. They both have a semicircle mark that needs to line up with the top of the board and the semicircle in the socket as well as the silkscreen.

Insert IDC Cables

First, you must make some IDC cables. Next, insert them into the headers. They're keyed, so they can only be inserted in one orientation. Yay!

Use It

The opto isolator is very easy to use. Since it just passes signals through it, you just hook it up between the two different devices you want to communicate. Additionally, you will need to properly hook it up to each devices power supply. The device is intended to isolate the circuits electrically, so each side needs to be powered independently.

The basic technique is this (with device A (sender) and device B receiver)

1. Attach +5v on device A to IN +5v
2. Attach GND on device A to IN GND
3. Attach up to 4 output signals on device A to the 4 IN inputs
4. Attach +5v on device B to OUT +5v
5. Attach GND on device B to OUT GND
6. Attach the corresponding outputs to device B

Opto Isolate the DC Motor Driver v1.1

The DC motor driver can generate a bit of line noise. In normal operation, this is not a problem. However, if you want to do more advanced things (like combining it with a quadrature encoder and doing edge-triggered interrupts) then you will want to use an opto isolator to keep things nice and clean.

Here are some instructions on how to use it with our DC Motor Driver.

Here are the basic steps:

1. Unhook DC Motor Driver from Arduino / Power / Motor(s)
2. Desolder connector wires from DC Motor driver
3. Solder in new wires from OUT IDC connector
4. Tape and secure newly soldered wires to prevent breakage
5. Wire up IN wires to Arduino as they were previously

Hookup Schematic

Hookup Pictures

Here is how it should look from the top:

Here is where to solder the red (OUT_VCC) pin to. It is the 5V pin of the voltage regulator: (check the flickr gallery for more pics)

Opto Isolate the Stepper Motor Driver v1.1

The stepper motor driver is a bit better when it comes to generated noise. However, opto isolation also protects against dangerous line spikes and such that could destroy your Arduino. There's probably even a minuscule chance that a non-isolated board could send dangerous current through the Arduino to your computer and fry something important. It's highly unlikely, but if you really want to be sure, its best to opto isolate.

Here are the basic steps:

1. Unhook Stepper Motor Driver from Arduino / Power / Motor / Endstops
2. Desolder connector wires from Stepper Motor driver
3. Solder in new wires from OUT IDC connector
4. Tape and secure newly soldered wires to prevent breakage
5. Wire up IN wires to Arduino as they were previously
6. Wire Opto Endstops directly to Arduino using the local Arduino GND/5V and the signal to the appropriate Arduino pin.

Hookup Schematic

Hookup Pictures

Here's a shot from the top:

Wire the OUT_VCC pin (red) to the 5V pin on the molex connector: (v1.1 / v1.0 of the Stepper Motor Driver has no voltage regulator)

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