A DDS function generator using an ATmega16

I still remember the piece of a rectangular box with many buttons labeled 1kHz, 10kHz, 100kHz, 1MHz, and everything else in between. Oh, it also has a knob connected to a dial dividing a sector into a hundred parts with a series of 7 segments changing dial every time a button is fired– just like old school radio we see at StarTrek. We commonly call it the function generator, and it’s usually used to inject square waves into your circuits – what for? Mostly for clocking. Here’s a new implementation of the AVR DDS function generator 2.0 (scienceprog.com); it has a different board layout and uses only through-hole components for easy construction. It has two outputs, one for a +-5V signal source and the other for a 0-10V signal source; the voltage levels of the two outputs are reconfigurable using two separate potentiometers. Like the original version, it incorporates a 2×16 LCD screen and pushes buttons for control – press a button to start and stop the signal generation. The circuit’s DAC is just a simple R-2R ladder controlled by…

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Ultraviolet light box for PCB exposure

Probably everyone electronics hobbyist is dreaming about fast PCB prototyping method. Some of you are just ordering professionally made PCBs, that is not always worth of cost; other are using an easier way – The laser printer toner transfer technique, which is not very accurate; the third option is more advanced – ultraviolet light exposure of photo-resist coated PCB through film mask. This gives pretty good quality at a reasonable price and doesn’t take much time.   The main thing that is necessary and expensive – the ultraviolet light source that is needed to expose a sensitive layer of PCB coating. You can buy light source, or as a hobbyist, you can build one. Scienceprog has published an excellent project on how to build an Ultraviolet light source. It uses 8x20W light tubes that give a total 80W for one side. So the exposure time is just three and half minutes. The device can be used for double-sided PCB exposure. And can produce a large number PCBs at once. Probably many of you may not need such a big device,…

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