Modeling auto ranging resistance meter using Arduino

Resistors are most common components in electronics. They are used to limit current flow, pull-up or pull-down voltage, scale down voltage and so on. If you are electronics enthusiast probably you have full bin of them. But when you are trying to pick one from a pile things start to be annoying. We know how those promises “I will keep them organized!” work. A plan B is to have handy robust tool to measure resistor value on the fly. Before soldering any resistor it is always a good practice to check if value is correct.


Praveen have shared his thoughts on how simple ohmmeter can be build by using Arduino and small amount of passive components. His meter measures voltage drop across unknown resistor and thus calculates resistance vale by applying Ohms law. He also implemented auto ranging feature to have best accuracy equally by measuring small or high value resistors. The trick here is by measuring voltage drop. If voltage drop gets too small, then ADC looses sensitivity. So Arduino simply selects different known resistor make voltage drop higher. Once measured resistor value is displayed on LCD screen. Circuit is really simple and easy to test-built on a breadboard.


Building bicycle pow effects with Arduino and WS2811 strips

POV displays are one great way of getting large images with only few LEDs. Spinning object with LEDs in them you can display messages, graphics and various effects. People like these things on bicycles, because it is fairly easy to build, but most important it makes you look different.

Balrog-k1n have shared his bicycle POV implementation. In his project he uses Arduino to send images through six WS2811 LED strips.

To give his creation interactive control and sense, he used 6+DoF sensor board which comes with Accelerometer, Gyroscope, Magnetic field sensor and barometer. Not all sensors are used here. In order to change light patterns he used neat method – since there are IMU unit, he can send control signals by taping breaks at different patterns. This doesn’t work 100% reliably, but seems it is enough to do the trick.


Water softener level detector

In places where water contains higher concentration of dissolved minerals is considered to be hard ware. It does not affect human health, but teapots, washing machines and dishwashers suffer from calcification. To avoid this problem, there are water softeners used where special salt is used to soften water. Of course this salt also dissolves and needs to be refilled time to time. David always forget to refill the tank because there is no visual indicator of it. So what you don’t see – you don’t care. To avoid future conflicts with his wife, he decided to add visual indicator to water softener.


On front panel he mounted LED bar graph where salt level is displayed. Also he added photocell to detect room light. It simply detect if someone is in the room or passes by by dropping a shadow. Other time bar graph is turned off. This hopefully prolongs life of LEDs and saves a bit of electricity. Another part is measuring salt level. Since salt is hard material, he used Sharp GP2D12 Infrared Distance sensor. It is able to measure distance from salt from 10cm to 80cm.


Programing Arduino over WiFi

In many situations you would like to program Arduino without any cables. For instance while testing mobile robots, or simply when your board is installed in not convenient position. So why not setting up an inexpensive WiFi connectivity to program Arduino on the run. Oscar have used ESP8266 based WiFi module.

He didn’t try to rewrite Arduino bootloader to work especially with WiFi module, but instead he wrote a processor program that listens for specific commands on coming from WiFi module. Once “reboot” command is received, Arduino resets and enters its stk500 bootloader. On PC side there is a Python server running which streams new firmware to chip. After software is uploaded, Program continues normal execution. [translated source]