Handy count-down timer

Probably you can thing about many ways to use a count-down timer. It could be simple kitchen timer, PCB exposure box controller, or some other specific places where counting down is needed. This particular project is really simple to build and has a bunch of handy functions: It uses two seven segment LED displays; Nice and intuitive button operations; Ability to adjust time while timer is running; Has one (can be two) output control pin. Nice thing is that author provides six versions of firmware where, where you can select one that suits you best. And of course in authors website there is really nice application where you can test timer operation on a browser window. Continue reading

Ultraviolet light box for PCB exposure

Probably everyone electronics hobbyist is dreaming about fast PCB prototyping method. Some of you are just ordering professional made PCBs, that is not always worth of cost, other are using easier way – Laser printer toner transfer technique which is not very accurate, third option is more advanced – ultraviolet light exposure of photo-resist coated PCB through film mask. This gives pretty good quality at 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 sensitive layer of PCB coating. Yo can buy light source or as a hobbyist you can build one. Scienceprog has published a nice project on how to build a Ultraviolet light source. It uses 8x20W light tubes that gives a total 80W for one side. So the exposure time is just three and half minutes. 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 big device, but some design ideas may be… Continue reading