A Clock Projector can project the time to a ceiling in the night.

There are lots of commercial alarm clocks with integrated clock projector on the market but I thought, it would be fun to build one myself.

Moreover it was a good project for becoming accustomed to the process of 3d-designing cases which can be 3d printed and to learn about designing tolerances.

The principle is easy – basically it works like a video beamer (or any other projecting clock^^).

LCD and Calculations

I choosed a small negative (background black) 64×32 LCD which has the dimensions of just 15mm x 12mm (active area 11.18mm x 5.58mm).

The goal was to build a complete projector with not more than 50mm x 50mm x 50mm (which I didn’t managed … But close to^^).

A small LCD has the advantage that everything becomes smaller and cheaper – this influences heavily costs for optics because a smaller LCD needs smaller optics to project an low distorted image.

Moreover a smaller LCD needs smaller focal length for a decent sized imaged on the ceiling. A good distance would be 2m from LCD to ceiling.

The formula for image width depending from the focal length is defined as:

with:
– S2 distance from lens to LCD and
– S1 distance from lens to ceiling
– W2 is the width of the LCD
– W1 is the width of the projected image

The formulas show that the smaller the focal length the larger the projected image will be.

I decided to go for 25mm because there are cheap lenses which can be obtained for about $12 in china.

For our values that would magnify the image by about x80 – 11.1mm LCD width would become 88.1cm image width on the ceiling in a distance of 2m.

Light and Condensor Lens

It was not really clear how strong a LED has to be in order to get a reasonable well readable picture in the night on the ceiling.

To be sure – actually I wasn’t really – I decided to use a high power LED with 1W and use a cheap chinese condensor lense to parallelize the light before it passes the LCD (this has do be done anyway but a condensor lens makes it possible to use more light because condensors are shaped in a way that allowes to get the lens as near to the LED as possible – so catching more light).

The two pictures show the condensor-lense which is directly mounted to the PCB the resulting light spot on the ceiling. It is a really gread lens which is made for my LED – so it fits perfectly and parallelizes the light nicely.

Electronics Construction

Two PCBs were designed – one holding the LCD and the actual projecting board.

The latter is equipped with 1W LED driver, STM32F103 Cortex ARM, a rotary encoder (for changing settings like brightness, standby-timer, time, …), USB, IR (both not used yet).

Mechanics Construction

Originally, I aimed for 50mm x 50mm x 50mm but I only managed to get to 60mm x 60mm x 60mm 😥 😉

Here an overview about all I designed:

From left to right: Case with DIY projection lens (I skip this part – it worked but not really well), Sony E-Mount, C-Mount. In the middle the rest.

LCD-Holder

A custom LCD-holder was designed to perfectly mount the LCD on the right place on the PCB.

Case – C-Mount Variant

There are incredibly cheap chinase C-Mount lenses with a focal length of 25mm. They are sooo cheap that image quality is really really bad when using for fotography.

But surprisingly it works (almost) perfect for the Mini DIY Projector 😀

The pillow-effect (optical distortion where the edges are not straight but bent outwards) is almost neglectable – resulting a much better image than I expected (after reading reviews to this lense)

Case – Sony E-Mount Variant

Just for fun – and because I have a 3d printer which works reliably without much attention – I did a variant for Sony E-Mount.

Here the projector with Walimex Pro 10mm 2.8 lens.

I have to admit – it isn’t that bright in reality but it’s still very readable although it is so large.

The image has more than 2m in width! And distortions almost non-existent 🙂

Downloads

Followig GitHub-Repository contains:
– Schematic
– Layout
– Bill of material
– STM32 Cortex ARM Source
– 3D-STL-Files
– Images

Link to GitHub Repository

STL-Files on Thingiverse

Documentation and Project site moved to:

https://gitlab.com/microengineer18/pidiver1.3/wikis/home

This is the site for the obsolete Altera DE1 proof-of-concept. Please look here for the PiDiver

Introduction

IOTA PoW needs a lot of computational power which makes sending transactions on smaller microcontrollers (like ARM) very slow. One of the main reasons is that the innerst loop of Curl-P81 can’t be computed very efficient on general purpose CPUs. Even modern CPUs with SIMD extension (like SSE or AVX) are heavily restricted when it comes to true parallel calculations.

This is a port of IOTA IRI’s Pearl-Diver for PoW-computation for FPGAs which speeds up the process of doing Proof-Of-Work significantly by a factor of more than 140 compared to e.g. a Raspberry Pi.

The core concept is that FPGAs are  able to calculate one round of Curl-P81 in a single clock cycle and one complete Hash in about 85 (including test for valid nonce). The core works 5-fold which means, in every 85 clock cycles 5 Hashes are calculated in parallel – this gives about 12.87MHash/s at a clock frequency of 220MHz. Moreover, the parallel computation can be adjusted easily to be even faster on larger FPGAs.

For instance, finding the nonce of a single transaction takes about 90s on a Raspi. Finding the nonce hardware accelerated by this core reduces the time to ~350ms.

This core can be also used by IRI when using a modified version which allows to use dcurl as external hashing libary.

So it is possible to build a full-node on raspberry pi with a decent hashing power for doing PoW calculations.

The project aims to be completly open source including all source codes, schematic, layouts.

VHDL-Core

The IOTA PoW Pearl-Diver core was implemented in VHDL.

Except an Altera PLL, no additional core or unusual VHDL library is used which makes it very simple to implement for other FPGA platform targets.

Moreover the core is customizable so the 5-fold parallelization can be increased or reduced (currently up to 8 but that could be changed with little work) depending on the resources of a FPGA target.

The core implements a high-speed SPI interface which directly can be used by the hardware SPI of a Raspberry Pi.

Following the electrical connections between Altera DE1 and Raspberry Pi.

Here the synthesis report for the EP2C20:

Maximum clock frequency:

First clock is I/O like SPI and commando decoder (running @ 110MHz in the design). Second clock is the actual Pearl-Diver PoW State-Machine reaching 220MHz.

Design is still functional although all of the optimizations 🙂

Pearl-Diver Core Repository

Following repository not only contains VHDL source for Altera DE1 and „Pi-Diver“ proto-type but also project-files for Quartus (Prime).

Altera DE1 Cyclone 2 is supported by Quartus 13.0.1 and Cyclone 10 is supported by Quartus 17.x. In the first case, you can directly synthesize the project and upload it to the Altera DE1.

Link to Github Repository

Hashing-Library dcurl with FPGA support

dcurl is a very fast Curl-Hashing-Library which not only supports graphics cards (OpenCL) but also provides highly optimized variants for SSE and AVX capable CPUs.

I did a fork of the library and added code for support of the VHDL Pearl-Diver.

The advantage is that every software working together with dcurl library can make use of the FPGA version of Curl (on Raspberry Pi – for different targets the low level control of SPI has to be replaced).

Link to Github Repository

Compiling and Testing with dcurl

1. Download and install BCM2835 library

# download the latest version of the library, say bcm2835-1.xx.tar.gz, then:
tar zxvf bcm2835-1.xx.tar.gz
cd bcm2835-1.xx
./configure
make
sudo make check
sudo make install

2. Enable „SPI“ under „Interfacing Options“.

sudo raspi-config

3. Load kernel module with modprobe

sudo modprobe spi_bcm2835

4. Check Permissions

pi@raspi:~ $ ls /dev/spidev0.0 -al
crw-rw---- 1 root spi 153, 0 May 3 15:17 /dev/spidev0.0

pi@raspi:~ $ groups
pi adm dialout cdrom sudo audio video plugdev games users input netdev gpio i2c spi

5. Clone and Compile dcurl library

git clone https://github.com/shufps/dcurl
cd dcurl
make BUILD_FPGA=1

6. Test library (for a reason I still don’t know SPI access only with „sudo“ possible).

cd build
sudo ./test-pow_fpga

parallel level detected: 5
Found nonce: 000c9b9c (mask: 00000008)
Time: 321ms  -  MH/s: 12.870

7. If there is no error then everything worked 🙂

Licence

This project is licensed under the MIT-License