DIY for Electronics

In this article a simple inductance meter is presented. It comes in handy when winding your own coils or transformers as needed in switching power supplies. It becomes even necessary for winding flyback transformers where the air gap must be adjusted. The oscillator circuit presented here is not my own creation, it can be found on various web sites. My contribution is the PCB design, the additional range switch and the buzzer.

When programming microcontrollers debugging is inevitable. Options like JTAG or DebugWIRE exist, but they are usually too expensive for most entry level DIYers. Another simple and controller-independent option is to utilise the USART for debugging. It's integrated into nearly all of today's microcontrollers. The only problem here is to convert the two serial signals RXD and TXD from the controller levels, usually TTL, to the EIA-232 levels as found in the serial port of every PC. Fortunately there is the MAX232, which converts signals between both levels.
This article describes how to build an extremely compact converter circuit built around the MAX232. With a size of just 14 x 17 mm (0.55 x 0.67 inch) the PCB is small enough to fit into a D-SUB plug housing