After some very busy months of assembling all the components, trying out different screen materials, playing with various housing designs and a lot of coding, we finally finished our new prototype.
I have uploaded pictures and a video of the working clock. BoM, CAD model and other details will be updated soon. Below are also some pictures from the assembly.
We finally finished the design of the Servo Wordclock. BOM will be updated soon.
All consumables and lasercut parts are ordered and will arrive soon.
We switched from the curved organic form to a more straight forward classic one. This prototype is designed to be "easy" to built - as far as you can say easy, when everything you build is multiplied by 114 ;-) . The Servo Wordclock is broken down into sub-assamblies to be pre-assambled in order to realise easy and faster building of the Servo Wordclock and in regards of warehousing and service cases.
Here are the pictures of our final design.
(Note that the screen is hidden to allow a better view on the mechanics)
The Housing for the Actuators (shown on last picture) will be printed in two parts and glued together due to print area limitations.
Now the print marathon begins!
We can't wait to finaly get all the parts together to start building this wonderful prototype!
As written in a previous log our plan was to control the clock via an android app using the BLE interface of an ESP32 microcontroller. However, we came to the conclusion that it would be more convenient to use the WiFi interface of the ESP. For one, a low energy protocol like BLE is not really needed since the clock is permanently connected to a power supply. Also WiFi functionality allows to update the time from an NTP server and therefore we can get rid off the RTC module. The clock functions will be controlled via a webserver that can be accessed from every device within the same network so there are no Android/iOS compatibility issues.
I already started programming the code which is based on andrei.erdei's VERBIS. Below you can see some preliminary screenshots of the web interface.
We have just ordered 125 custom PCBs for the WS2812B LEDs on PCBWay.com. For the previous prototype we just cut an LED strip into 114 pieces, glued these onto a 3D printed panel and connected them again with wires. Since each LED needs 6 connections, the preparation of all wires (cutting, stripping and tinning) and soldering them took a huge amount of time. Now we will get preassembled PCBs that include JST connectors for easy wiring.
Eagle and Gerber files for the PCBs can be found on the linked GitHub page.
This is how 120 pcs of MG90S servo motors look like. We also received 20 pcs of PCA9685 driver boards. Each one of these can control 16 servo motors and interfaces to the MCU via I2C.
I recently got an ESP32 development board which will be replacing the Arduino Nano that we used for version 1. The idea is to control the clock from an smartphone app using the Bluetooth Low Energy (BLE) functionality of the ESP32.
For a first test I used the example code written by arduinofanboy to turn an LED on/off. I was also able to control the servo motor using the same app. The next step will be to write an app that can fully control the clock and will be replacing the IR remote that we used in the first version.
The most important part of our Servo Word Clock are of course the servo motors. For our previous clock we used SG90 nylon gear servos. Although they were labeled with the popular brand Tower Pro they were obviously cheaper Chinese knock-offs. For the new version of our clock we decided to switch to the more robust metal gear servos MG90S. To keep the price low original Tower Pro servos are still not an option but we ordered some servos from the Chinese brand MiToot. This should at least allow us to get consistent quality in contrast to ordering unbranded servos.
The servos we ordered were delivered very quickly and I let them running for a few hours without any of them failing. While this does certainly not count as a thorough lifetime test we felt confident enough to order 120 pcs that will be used to build the next Servo Word Clock prototype.
We are planning on using an acrylic plate as screen on which the letters are projected from the back. I have ordered several samples of white acrylic with varying optical transmission. Unfortunately, the outline of the letters is always blurred on the acrylic sheets. This is because the light is diffused too much within the plates which are rather thick (2-3 mm). Therefore, the current plan is to use a thin semitransparent foil (similar to the previous version of our clock) which will then be attached to a transparent sheet of acrylic. As can be seen in the last picture, the projection has a sharp outline on the foil.
Moritz v. Sivers
