Testing stepper motors with pulse generator

This is a quick portable circuit used to test stepper motors. It is based on small PIC 12f675 microcontroller. The pulse speed is changed with potentiometer. It allows smoothly variate between 20Hz and 3kHz.


It has couple jumper bridges to select enable and dir pins. Servo tester is powered with four NiMh rechargeable batteries that give total 4.8V.  This circuit can also be used as general purpose pulse generator if needed.


Arduino portable sensor pack with Bluetooth LE

Human have only five senses, but there are huge amounts of data that we cannot see or feel. This can be fixed with a bunch of sensors. IntensePancake share his instructable where he built a sensor pack that sits on top of Arduino ans talks to Android device via Low Energy (LE) Bluetooth channel. Sensor pack is built on custom prototyping board where he mounted all sensors. The list starts with its own voltage regulator. Since Sensor pack meant to be portable, on board linear regulator seemed to be inefficient (bellow 50%). So he bypassed it with switching regulator LM2825N which promises about 80% efficiency. With 9V and about 560mAh battery it worked around 13 hours.


He’s chosen nRF8001 LE bluetooth breakout board from adafruit. It is interfaced to Arduino via SPI interface. Lets get to sensor list. Firs one is Si1145 light sensor which packs several features including visible light intensity, infrared light intensity and UV index which allows to predict UV exposure. Another sensor id BMP180 barrometric pressure sensor which can be used as altimeter. It also includes temperature sensor. Going further there is well known DHT22 Temperature/humidity sensor which measure humidity and temperature. Second part is Android application. The interface is really easy to follow – all sensor data is displayed in human readable form. Project files can be found on GitHub.


Getting most of Arduino with sensor extension board

Arduino like any other microcontroller platform is quite useless without connection to real world. It has digital and analog input and output pins where various sensors and actuators can be plugged in. And this is where real fun begins. Arduino is famous of being easy to use, rich in libraries that support almost every popular sensor, transducer or other module. If you want to learn how embedded systems work, Arduino is great starting point. I suggest starting with simple sensors like switches and LED flashers. Once you are getting better go ahead and plug more advanced sensors like temperature or ultrasound.


Having everything conveniently organized can be tricky. But thanks to Arduino Sensor Expansion shield, most of sensors can be connected and programmed much easier. Continue reading


Building capacitance and inductance meter

Capacitor and inductor are like brother and sister. They both are reactive components with somewhat similar characteristics. Like any other electronics component you need to know its value before putting in to circuit. Capacitors are a bit easier as they are pretty good labeled. Inductors are different story. Some of them are labeled, but what if you want to make your own – then you can calculate its value (what is not always so easy) or measure. Most multimeters come with capacitance meters, but only few have inductance measuring option. BasinStreetDesign from instructables decided to build capacitance/inductance meter that would be accurate enough for his daily use.


He considered several measuring methods including resonance, time constant and impedance. Resonance seemed to be most accurate. Measuring frequency and calculating component value definitely involved microcontroller that he wanted to avoid. Interesting thing is that he used UV erasable PIC microcontroller. Most of young hobbyists probably never seen this before. So the project got some smell of retro. Anyway further journey took everything to AVR. He had some struggle by setting things up and writing software, but eventually digits lit up asking for further calibration. He put schematic in to tin can, painted and labeled.