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.
BASIC programming language was founded back in 1964. Its main goal was to enable people to use computers for their need the easier way. BASIC is generally a high level programming language that from simple form evolved in to modern programming language like Visual Basic .NET. Anyway simple forms of BASIC language still exists and are used in several areas. Microcontrollers are one place where it fits pretty well. Dan has been doing projects with BASIC functionality. His earlier work was done on building Arduino BASIC shield. But eventually he saw the limitations of such approach like low TV out resolution and Arduino dependence.
Having these in mind he decided to build a standalone BASIC computer based on ATmega128P. Using stand alone solution these problems were gone. BASIC computer has a PS/2 keyboard support, TV out and the rest GPIO headers for interfacing purposes. BASIC programs are stored in AVR EEPROM memory. Microcontroller runs TinyBASIC Plus which supports most of common BASIC commands including IO support, system commands, storage, math, etc. BASIC computer is assembled using only through hole components, so building one is really piece of cake.
Soldering is necessary part of electronics prototyping and production. If you are getting serious in to this you probably noticed that not all parts can be soldered with iron or heat gun. Some electronics parts you may want to use are BGA or QFN that require different soldering techniques. What manufacturers do, they are using reflow ovens to solder all SMT parts at once. Oven soldered boards look professional and save time. There is no problem to build reflow oven for home use. All you need is toaster oven with convection and controller which you will most likely have to build by yourself.
Henrik built such controller by using ATmega8U2 microcontroller with USB support. He traced custom board where he put MAX31855 thermocouple to digital converter. Thermocouple is number one choice for sensor where things get really hot. Controller controls oven heater through solid state relay. Controller firmware is based on PID control algorithm that helps to get close to desired temperature curve. It is important to follow temperature profile (temperature vs time) while soldering in order to succeed.
Jan shared his small project where he built a police light simulator using couple blue LEDs and Attiny25 (or other tiny’s from series 25/45/85). Each channel can drive up to 500mA so LEDs can be replaced with LED stripes or bulbs. There are couple effects programmed in that are controlled by using PWM.
This project came to mind when repairing toy police car. But this schematic could be used to prank friends or for other purposes. Be sure to check if using it in public wont break the law.