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Construction guide


This guide will take you through the process of modifying a projector, based on our work in the SPECTRAL Wandering Sounds and Images seminar. Most of this guide is focused on an Eiki R, but you can apply the same principles to any projector. (The Euming P26 projector is rare outside of Austria, but the Eiki is common worldwide.)

Theory of Operation

The projector's motor is replaced with a 540 sized motor (intended for radio controlled model cars). The lamp is replaced with a powerful LED and constant-current driver. The shutter is replaced with a rotary encoder that reports the drive-shaft position to the ESP32 micro-controller 100 times per revolution. The ESP32 takes inputs from knobs and switches and produces PWM signals to control the motor and LED, which blinks to simulate the shutter. For optical sound, a red LED illuminates the optical track and a photodiode preamplifier boosts the signal to line level. The projector is powered by a 3S (11.1v) RC car battery mounted inside the projector (with optional DC input for external power supply).

The behavior of the projector is defined by Arduino-compatible code. When compiling the code, you can easily enable/disable features to match your hardware. (Example: Our Eumig P26 projectors have simple controls, but the Eiki has more options. They both share the same code-base.) The code has hidden features like an FPS meter and frame counter that are not currently used, but could be incorporated into future designs.

The major parts of the system are shown in this diagram, and described in detail in the sections below.

Major parts diagram—-

Difficulty : not so easy

Duration: depends on your skills with electronics (see below)

Cost :about $$$ (see detailed Bill of Material )

Skills needed

You need to be comfortable with 3D-printing, electronics and soldering, micro-controller programming, and working with hand tools (drilling/tapping).

Tools needed

3D printer, hand tools, soldering iron, heat gun, metric drills and taps

Choose A Projector to Modify

Do you want a small, portable projector for film loops, or a larger one with sound that can support full-size reels? What about cost and availability?

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Test the projector, purchase parts, remove un-needed components, etc.

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Camtank and Shutter Pulley

The camtank contains the pulldown claw mechanism. The original shutter and pulley mounts to the outside, with a still-frame clutch lever in between. We will remove the pulley, shutter and clutch mechanism. We will replace the pulley with a new one, and mount the encoder magnet on the shaft.


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User Interface

The modified projector controls replace the original knobs on the side of the chassis. You can choose to include basic or advanced controls to suit your needs (Do this first because it requires a lot of drilling into the projector chassis. When viewed from the inside of the projector, these controls are the “deepest” layer so they will be partially hidden by later steps.)


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Power Safety

The projector's power system needs careful attention to safety. Lithium batteries are a fire risk if short-circuited, and they can supply enough current to quickly destroy the projector electronics in case of a fault. This page describes the protections that you will build in the Power Wiring step.

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Power Wiring

There are 2 possible power sources: A 12V DC adapter (via 5.5/2.5mm coaxial jack) or a 3S LiPo RC car battery (via XT60 connector). A 3-position SPDT switch selects DC / OFF / Battery. The switched power flows through a fuse and DVB01 power protection board before landing at a pair of terminal blocks near the motor. This is the connection point for the LED driver and cooling fan, as well as the motor. The motor has a built-in regulator that supplies 6V DC to the micro-controller and other low-voltage circuits.


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ESP32 PCB Mount

The micro-controller wiring comes later, but first we need to 3D-print the slotted mount to support the right side of its PC board.


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Motor Prep and Wiring

The Hobbywing “Quicrun SE” 1200kv motor is made for radio controlled trucks. It is a brushless DC motor with built-in ESC (speed control) and uses FOC (field oriented control) to create smooth movement at low RPM while maintaining high torque. This is a BIG benefit for projection at slow speeds. (Other “540 size” DC motors and ESCs will also work, but they probably won't move smoothly at low speeds.) The micro-controller will send a PWM signal to “impersonate” an RC receiver, but there are several things we must do to prepare the motor first.


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Motor & Belt Installation

Attach the motor to the 3D-printed adjustable mount using the aluminum motor bracket. Add a 16 tooth GT2 pulley to the motor shaft via an 1.8“ to 5mm adapter. Mount the motor in the projector and tension the shutter timing belt.


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Encoder Wiring

The AS5047D magnetic encoder senses the rotation of a small magnet on the shutter shaft and reports its angular position to the micro-controller.


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Encoder Mounting

The encoder board must be positioned within a few millimeters of the magnet on the shutter shaft.


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LED Driver Wiring and Mounting

High power LEDs need careful current regulation using LED Driver circuits. We use the TaskLED H6cc, which has a dedicated PWM pin for lamp dimming.


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LED Module Assembly

The Cree XHP70.3 HI LED needs to be mounted to a fan-cooled heatsink. To focus the light on the film frame, we will use a combination of an aluminum reflector and a condenser lens. Everything will be mounted on a sliding rail to permit focusing.


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Rear Door & Battery Meter

Eiki R & N series projectors have a hinged rear door that opens without tools. This makes it easy to change the battery and troubleshoot any problems. After removing the AC transformer and motor, we can modify this door to make the projector smaller.

The ESP32 could monitor battery voltage and alert the user, but it would require a voltage divider and more pins for the ADC input and a visual indicator of some sort. Pre-made battery monitors are cheap and easy, so let's use one!


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Optical Sound

We replaced the BRK exciter lamp with a high brightness red LED, and built a preamp to amplify the optical pickup to line-level.


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ESP32 Wiring

The ESP32 micro-controller is the heart of the projector, so there are a lot of connections to make. We use color-coded wires and connectors to make the process easier.

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ESP32 Programming

The micro-controller code is written in the Arduino programming language. Use the Arduino IDE to customize the code to match your projector and upload it to the ESP32.


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Program the ESC

The motor's internal ESC (electronic speed control) has settings that we need to change.


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Synchronize the Shutter

Before projecting film, the digital shutter needs to be synchronized to match the film movement.


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Calibrate Motor Speed

The motor / ESC uses the RC car “servo” protocol to indicate speed (50Hz PWM signal with pulse-width from 1000uS to 2000uS). RC receivers have sloppy timing so all ESCs have a calibration process to adapt their timing to the receiver. In our case we leave the motor / ESC at the default settings and calibrate our speed using code.


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Focus the LED

The LED module needs to be adjusted to produce maximum brightness and even illumination. Do these steps in a projection environment, but without threading film.


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Check these steps if you find that something is going wrong!

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Further Research & Upgrades

A list of future upgrades we're considering, and ideas for you to extend the project.

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en/meetings_projects/spectral/mire-wandering/wandering-16mmprojection/construction_guide/start.txt · Last modified: 2024/05/14 16:07 by zach