Wave guide for Ultrasonic Sensor (HC-SR04)

Ultrasonic level sensors work by measuring the time of flight of a sound wave. The wave must travel in a clear path to and from the top of the liquid being measured in order to provide an accurate liquid level measurement.

As with any wave, the sound pulse generated by the ultrasonic sensor does not travel in a straight line, but rather expands as a function of the distance traveled. As the wave widens, it will bounce off of anything in its path. In many cases this is not an issue, but, occasionally, conditions within the tank or vessel being measured cause sound waves to be reflected from objects or surfaces other than the intended target.

Detecting the wrong target causes inaccuracy or false readings from the sensor. Things like large weld seams, pipes, mixers, or access hatches inside tanks can present false targets to the sensor. The use of a standpipe as a waveguide for the sensor can help eliminate these problems. 

A standpipe serves as a waveguide to focus the sound wave away from possible false targets and directly onto the desired liquid target. Any smooth-walled tube or pipe can serve as a waveguide as long as care is taken to de-burr the end of the tube and cut the end at a 45° angle. This avoids the creation of standing waves inside the tube.

Use of a standpipe may affect the maximum sensing range of the level sensor because the waveguide also serves to limit the sound energy coming back to the face of the sensor. This should be taken into consideration when applying a waveguide.

Let us know if you have any questions about using a standpipe as a waveguide for an ultrasonic sensor. Level measurement can be drastically improved when the circumstances are just right, and the standpipe is applied properly.

Quality problems

Good quality 3d printing relies on people, equipment, material, method and environment. First of all, the people who operated or used the technology must have knowledge at printing. Basic training on set up, design of object and properties of raw materials such as strength, elastic modulus, melting temperature and Max. angle or span of printing.

The next problem is the equipment. Calibration of printer must be carried out prior to use. Bed and hot end temperatures shall be determined according to materials and shape of printing. Suitable supports or brim are required in case of doubt.

Harmonic Gear

Timing belt harmonic gear – this is a harmonic gear (Strain wave gear)with the use of timing belt such that less gears are required to make. It can be easily available and maintained. 3mm pitch 15mm width timing belt (2703M 15), 90 teeth gear timing belt holder (Red in colour) and 92 teeth gear driving casing ring (Black in colour) which were driven by the rotating arm with two bearings (12mm dia.) at each end.

Strain Wave Gear

LAMP & WordPress

Step 1: Linux Distribution

In order to install LAMP (Linux Apache MySQL and PHP), you are required to install a linux distribution as first. For my case in Raspberry Pi 3, (i.e. Raspbian)in 「NOOBS」 can be downloaded or select a distro as you wish.

Step 2: Apache

Web server such as Apache2 (or Nginx) can be installed via command line after login as root or administrator. You are suggested to update and upgrade the system then install the apache2 as below. Default directory /var/www/html/ and a static page index.html will be created in local at Port 80.

#sudo apt-get update

#sudo apt-get upgrade

#sudo apt-get install apache2 -y

Open your web browswer and type in http://localhost:80, a web page is showing 「It work」. Then, it is mean that your web server is working.

Step 3: MySQL

MySQL is an open source database server which provide a core for searching and storage of dynamic data of user and web content. Modules can be installed to link other programming language and functions.

#sudo apt-get install mysql-server mysql-client

Step 4: PHP

PHP is a programming language with full range of functions to react with web browswer, database and system calls.

#sudo apt-get install libapache2-mod-php7 php7 php-pear php7-xcache php7-mysql php7-curl php7-gd

#cd /var/www/html

#sudo rm index.html

#sudo echo 「<?php phpinfo(); ?>」 | sudo tee index.php

#sudo service apache2 restart

Open your web browswer and type in http://localhost:80, a web page is showing 「Information and status of PHP」. Then, it is mean that your web server and php are working.

3D Printed – Watch Winder

This is a 3D printed watch winder which was driven by a geared motor and a 24×7 digital timer. 5V USB adopter was used to provide power to motor. Stainless steel watch pins were adopted for the axles of main gear which driven two watch enclosures to rotate 360 degree either clockwise of anti-clockwise. To ensure both watches are rotated/winded continuously without any damage or stop, cushioning was used to fit the watch into the encasement.