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  • 7/27/2019 Improved Optical End-Stop.pdf

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    http://www.instructables.com/id/Improved-Optical-End-Stop/

    Food Living Outside Play Technology Workshop

    Improved Optical End-Stopby Jason-Bon August 20, 2012

    Table of Contents

    Improved Optical End-Stop ......................................................................................................

    Intro: Improved Optical End-Stop ...............................................................................................

    Step 1: The Design .........................................................................................................

    File Downloads ...........................................................................................................

    Step 2: Assembly and Operation ...............................................................................................

    Related Instructables ........................................................................................................

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    Intro: Improved Optical End-StopI am in the process of building a Rep Rap Prusa 3D printer, and I have this habit of trying to re-invent the wheel. I started researching electronics and really dislikedeverything I found,

    I had originally ordered some gen 2.1 Opto boards, which I decided were too large for the printed clamps.

    After some research I found the most recent End-stop http://reprap.org/wiki/Gen7_Endstop_1.3.1, looks like somebody's after-thought.

    So I decided to design my own....

    Step 1:The Design

    I started with the schematic from the Gen 7 end-stop and went from there. My biggest problem with the schematic is that the output signal (probably) will not give a 5vhigh output, according to my math the output will range from 0- 3.7v. I'm sot sure what a digital input pin on an arduino will accept as a high but I would rather the outpcould go the full 5 volts.

    I used the same photo-interrupter TCST2103 and corresponding current limi ting resistor as well as the pull up resistor for the photo-transistor.

    It needed to have an led for debug purposes but I couldn't decide on the final wiring, so I left 3 different component landings near the end of the board. The idea is for builder to use whatever landings they feel necessary: led on all the time, led on when the sensor is blocked and led on when the sensor is not blocked. Use the 2nd onwith caution because it will also have an output high of 3.7 volts.

    The board was carefully sized to fit onto a Prusa End-stop holder with minimal overhang. The connector is placed at the end of the board so the wires can be routed oof the way.

    Board Parts:The board (3 ordered from http://oshpark.com/for around $5)TCST2103 Photo-interrupterblue led (surface mount 0805)180 ohm resistor (surface mount 0805)

    2.2k ohm resistor (surface mount 0805)2 - 1k ohm resistor (surface mount 0805)Plus a complete assembly of a ~.1" pitch male/female connector (don't forget pins), or solder wires directly to the board. This project was designed to use a 2.5mm pitJST connector.

    Mounting Parts(assuming mounting to Prusa):Printed end-stop holder2 - M3X18 screws or similar3 - M3 nuts2 - non conductive spacers or small diameter washers to space the board from the printed holderM3X25 screw

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    http://www.instructables.com/id/Improved-Optical-End-Stop/

    File Downloads

    Opto.brd(6 KB)[NOTE: When saving, if you see .tmp as the file ext, rename it to 'Opto.brd']

    Opto.sch(8 KB)[NOTE: When saving, if you see .tmp as the file ext, rename it to 'Opto.sch']

    Step 2:Assembly and OperationThe three component landing on the top of the board allow for 3 dif ferent led/resistor combinations, its up to you to choose one:Option1 - Place the resistor on the "G" pin of the connector and the LED on the "V" pin with the anode pointing away from the Photo-interrupter. The LED will be on aslong as the board is powered.Option2 - Place the resistor on the "G" pin of the connector and the LED on the "S" pin with the anode pointing away from the Photo-interrupter. The LED will be on whthe Photo-interrupter is blocked.Option3 - Place the resistor on the "V" pin of the connector and the LED on the "S" pin with the anode pointing towards the Photo-interrupter. The LED will be on whenthe Photo-interrupter is not blocked. (recommended)

    Assembly will vary on what kind of tools you have on hand, I used a hot air re-work station and solder paste. Generally you should probably start with the surface-moucomponents and then move onto through-hole.

    Surface-MountR1 - 180 ohm, Emitter current limiting resistorR2 - 2.2k ohm, Signal pull up resistorLED/1k ohm Resistor combination

    Through-Hole

    TCST21032.5mm JST connector

    Then all you have to do is mount it.

    The Signal will be LOW when unblocked and HIGH when blocked, The board should be powered with 5 volts, the resistors must be changed if you need to use a diffevoltage.

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    http://www.instructables.com/id/Improved-Optical-End-Stop/

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