Quick Review of a cheap Chinese component tester

Adam Fabio has posted a quick review of a cheap Chinese brand multifunctional component tester on Hackaday. He found its build quality was very cheap, but he was also amazed with its features and functionalities, including ohmmeter, capacitance meter, transistor tester, etc, which worked amazingly well with a reasonable accuracy. Powered with Atmega328 microcontroller, this component tester can be purchased for ~ $20 on eBay and Aliexpress.

Transistor tester

Inexpensive Transistor tester from China

I didn’t have huge expectations for the tester, but I hoped it would at least power up.  Hooking up a 9 volt battery and pressing the magic button brought the tester to life. Since I didn’t have anything in the socket, it quickly lit up and displayed its maker information – “91make.taobao.com”, and “By Efan & HaoQixin”, then it informed me that I had “No, unknown, or damaged part”.

I had a few resistors lying around the bench (doesn’t everyone?) so I put one in. The tester read it as 9881 ohms. Sure enough, it was a 10K 5% resistor.  Capacitors – ceramic disc, electrolytic, and surface mount all worked as well. The tester even provided ESR values. The real test would be a transistor. I pulled an old  2N2222 in a TO-18 metal can, and popped it in the tester. The damn thing worked – it showed the schematic symbol for an NPN transistor with Collector, Base, and Emitter connected to Pins 1,2,and 3 respectively. Flipping the pins around and re-testing worked as well. The tester showed hFe as 216, and forward voltage as 692 mV, both reasonable numbers for a 2N2222.

DIY bike speedometer

Check out this detailed build of Arduino-powered speedometer to monitor your bike speed on road. The project uses a reed switch to sense the rotation of one of the bike’s wheels. The Arduino reads in the reed switch closings and calculates the bike speed in mph. The calculated speed is displayed on a LCD screen. The speedometer is calibrated by defining the radious of the wheel in the firmware.

Arduino bike speedometer

Arduino bike speedometer

Secure both the magnet and reed switch to your bike wheel with electrical tape (either wheel is fine).  As shown in the images above, the magnet connects to one of the tire spokes and the reed switch connects to the frame of the bike.  This way, each time the bike wheel turns the magnet moves past the switch. Connect the leads form the reed switch to the long wires from your protoboard (orientation does not matter here- it’s just a switch)

Onion Omega: Another WiFi dev board for IoT applications

Only 1/4 the size of the Raspberry Pi computer, Onion Omega is the latest and most promising open hardware development platform for WiFi based IoT applications. It comes with built-in WiFi, Arduino-compatible and it runs full Linux. It lets you prototype hardware devices using familiar tools such as Git, pip, npm, and using high level programming languages such as Python, Javascript, PHP. The Onion Omega is fully integrated with the Onion Cloud, making it a breeze to connect physical devices to the Web to create Internet of Things applications.

Congratulations to the Onion Team for far surpassing their Kickstarter funding goal, while there are still 11 days for the campaign to go.


Onion Omega is only 1/4 the size of RPi


Onion Omega Features

Onion Omega features:

  • Dimensions: 28.2mm x 42mm (1.1″ x 1.7″)
  • CPU: Atheros AR9331 400MHZ MIPS 24K
  • RAM: 64MB DDR2 400MHz
  • Flash: 16MB
  • WiFi: 802.11b/g/n 150Mbps
  • Ethernet: 100Mbps
  • GPIO: 18
  • USB: USB 2.0, Supports additional USB Hub
  • Power: 3.3V
  • Antenna: PCB Antenna w/ uFL Connector
  • Power Consumption: 0.6W


Hacking IKEA LAMPAN table lamp

Last month, we looked at a IKEA Molgan Lamp hack and adding ESP8266 connectivity to it. Here is another IKEA lamp enhancement project by Jesus Echavarria from Spain, where he hacked IKEA LAMPAN to include features like manual RGB controller to set the light colour, a timeout to turn off the light after 30 minutes without changes and a bluetooth connection to control the lamp with a smartphone or tablet.


Modified IKEA Lamp controller

Adding Bluetooth RGB controller to IKEA L

Adding Bluetooth RGB controller to IKEA LAMPAN

The system is based on a PIC18F2550 microcontroller, with a 12MHz external crystal. This allows run up to 48MHz internal code (using the internal PLL), necessary to manage the RGB leds. The RGB led’s I use are this ones, that has built-in the WS2811 controller (are compatible with Adafruit Neopixel ones). I use 8 leds for the lamp illumination. Note the 100uF capactitor (C3) near of the led connector, to prevents the initial onrush of current from damaging the pixels. Also, R2 resistor (330 ohm) is bwtween the microcontroller pin and the first led to prevent voltage spikes. Check Adafruit Neopixel Guide for more info.

Improving PWM-to-Analog voltage conversion

Modern day microcontrollers are equipped with one or more dedicated PWM peripherals built-in that can be used to generate analog output voltages with varying range by just using a basic RC filter circuit. While this is a very simple and practical approach, it has some limitations such as it can only drive high impedance load and the processor should continuously output the PWM signal to maintain the output voltage constant, which prohibits the processor to be put into a low power shutdown state when required. This application note from Linear Technology describes the use of LTC644 and LTC2645 chips, which are dual and quad PWM-to-voltage output DACs, to overcome these problems by directly measuring the duty cycle of the incoming PWM signal and sending the appropriate 8-, 10- or 12-bit code to a precision DAC at each rising edge.


Improving PWM-to-Analog conversion

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