Category Archives: hardware

555 Project part 2

From design to PCB

This year with students back in the classroom it was time to resume the development process. I was able to use a professional development day in Term 2 to finally get to grips with KiCad. I had already looked at a tutorial so using that as a reference I started the process to turn this circuit into a finished PCB that I could use in classes.

Eeschema editor

Following the steps in the KiCad tutorial I was able to create the circuit, then export this to a board design, choosing the appropriate footprints for components. Next step was to do the layout and connect up the tracks.

Finished PCB layout in KiCad

KiCad has a very neat 3D viewer which means you can view a finished board before it even gets produced.

The 3D viewer even populates the board with components

Previously I had ordered some PCBs from others’ designs from PCBWay as a test. From KiCad I was able to export my board layers as Gerber files. PCBWay has a quick feature where you just upload the Gerber files and it does all of the configuration. Their prototype rate means that you can get 10 boards made for just USD$5, but unfortunately the shipping costs rather more. Nevertheless, the service is incredibly quick, from submitting the order on Wednesday to receiving it on Monday morning, from China to Australia. The unit cost will come down when I order larger numbers for production.

10 + 1 for free!

When the boards arrived, 5 minutes work with the soldering iron and a finished product.

Success!

555 project part 1

Two years ago I had my students prototyping a simple 555 based LED flasher circuit on breadboards.

Prototype on mini breadboard

The next step involved transferring this to strip board so they could make a permanent circuit to take home. This part of the process proved troublesome as Veroboard is difficult to work with due to the close spacing of tracks, and the inability of students to follow placement instructions precisely.

In 2020 we started the year, but then COVID-19 intervened and students did not attend school, so did not build physical projects or do soldering.

Rotel amp restored

Picked up a couple of dead hi-fi amps, one of them being this nice Rotel RA-820. Opened it up, gave it a clean and replaced all the electrolytics and back in business. Now sitting in the garage hi-fi cabinet for when I’m working down there.

Useful links:

The other amp is a Cambridge Audio A-300 (like this A-500) but it looks to be in rather a sorry state, with at least one blown output stage. Have to work out whether that one is going to be worth restoring, or may get rebuilt as a chip amp …

NodeMCU electronic switch

Here’s a really easy demonstration of how you can control outputs on the NodeMCU with a simple web interface. The NodeMCU runs as a simple web server, writing a control panel interface directly as HTML.

Hardware

The circuit is very simple, just four LEDs with resistors wired to outputs of the NodeMCU.

wiring diagram
wiring diagram

Here’s the wiring I used, which matches the code.

  • yellow – D1 = GPIO5
  • green – D2 = GPIO4
  • blue – D3 = GPIO0
  • red – D7 = GPIO13

In Arduino code, GPIO numbers map to Arduino digital outputs, so to turn on yellow LED use digitalWrite(5, HIGH)

NodeMCU circuit
NodeMCU circuit

Software

  1. Get the code example (esp8266ledControl.ino) and edit to add your wifi name and password to the code.
  2. Board type in Arduino IDE is ‘Node MCU 1.0 (ESP-12E Module)’
  3. You will need to set up your Arduino IDE to work with the NodeMCU. A good guide can be found at https://www.circuito.io/blog/nodemcu-esp8266/ (go to the last section Programming NodeMCU with Arduino IDE. Note there is a slight typo in the instructions, the board URL should end with ‘.json’ not ‘.jso’).
  4. Upload the code to the NodeMCU.
  5. When it has finished loading, quickly open the Serial Monitor, set the baud rate to 115200.
  6. Wait until the device joins the WiFi network, and note the IP address it obtains.
  7. Enter this address in a web browser, and the interface will load.
  8. Now you can turn on and off the various coloured LEDs by clicking on the respective buttons.

web interface
web interface

Silicon Chip module articles

A series of articles on ‘Cheap Asian’ Electronic Modules

  1. Low Cost Asian Electronic Modules (Oct 2016)
  2. Computer Interface Modules (Jan 2017)
  3. Measuring Temperature and Relative Humidity (Feb 2017)
  4. LCD Module with I2C (Mar 2017)
  5. Direct Digital Synthesiser (Apr 2017)
  6. LED Matrix Displays (Jun 2017)
  7. Li-Ion and LiPo Charger Modules (Aug 2017)
  8. Pressure/Temperature Sensors (Dec 2017)
  9. 2.4 GHz Wireless modules (Jan 2018)
  10. Sensing motion and moisture (Feb 2018)
  11. ESP-01 Wifi Data Transceiver (Apr 2018)

We have vision!

I bought a Raspberry Pi camera to go with the RPi 3 for the school project. The eventual intention is to put it on our tank robot so we can see what it is seeing.

Following on from the previous tutorial IoT: Raspberry Pi Robot with Video Streamer and Pan/Tilt camera remote control over internet I installed streaming software, plugged in the camera and crossed my fingers. Loading the page showed some promise except I’d turned the lights off in the server room when I went away, so I had a square of black. Back to the server room, then back to my computer to find I was looking at the roof of the server room.

It works!

First view from the pi camera. The server room ceiling, not the most exciting view.
First view from the pi camera. The server room ceiling, not the most exciting view.

Science Talent Search – Robot Buggy

My son entered Science Talent Search with this Arduino-powered buggy. We used IR with a TV remote to issue codes for motor control and combinations of colours for the RGB LEDs.

Programming was fairly simple, but we found issues with power. It seems that motors are very noisy and when they run it can reset the Arduino. We solved this by running the motor off 4 x AA batteries, whilst the Arduino is powered by a phone battery booster. The Arduino in question is actually a Freetronics Leostick, which is a nice small board, and has a USB plug which we just plugged straight into the phone battery.

New Raspberry Pi 3 setup

This is the second Raspberry Pi I’ve bought, this one is for school projects. The really neat feature is that it has built-in WiFi.

  1. Download NOOBS and copy onto a MicroSD card
  2. Put in the MicroSD card and boot the RPi, then run the installer
  3. After a while, it restarts and you get the desktop. At this point it was easy just to join the home network and we’re done to this point
  4. At school, we set up a fixed IP address on a hidden wireless network, and used the MAC address to secure access to the network
  5. Proxy settings needed to be added
  6. Now, to run some updates. First apt-get update, then apt-upgrade
  7. Install vncserver so we can connect remotely using Chicken of the VNC

Now it’s time to tackle some specific jobs we need for projects.

  1. I used this article IoT: Raspberry Pi Robot with Video Streamer and Pan/Tilt camera remote control over internet to install lighttpd so now we have a simple web server running on the Pi . I wrote a simple page in Nano to test that it works