As my main interest is in getting people up and running with their own Phifact I’m not going to spend too much time describing the operation of the electronic circuit but here are a few notes…
1) Both the PICAXE chip and the LCD screen require a 5V power supply. Any higher than 5.5V and you could damage the components. Lower than 4.5V and the LCD screen may become dim and hard to read. The simplest solution is to use 4 AA rechargeable batteries. These supply a voltage of 1.2V each and enough current to provide a good working cycle per charge. You could use other power supplies but you would need to include a voltage regulator and associated components in the circuit. You must not use 4 AA alkaline or aithium batteries as this will damage the components.
2) There are lots of ways that the circuit could be changed to provide different features but I wanted to keep the Phifact relatively simple. If you want to make changes to the circuit that’s great and I’d love to know what modifications you have made but please don’t ask my advice about circuit modifications as I’m no electronics expert.
3) The PICAXE 28X2 was chosen because of its low cost and the easy method of programming. You could replace the PICAXE chip with a Microchip PIC which would have several advantages (faster instruction cycle, more compact code) but you need a special device to program a PIC and a lot of knowledge. Again if you want to experiment with programming a custom PIC then I think that’s a great idea but please don’t ask me for coding help.
The circuit diagram is split into two parts, just because it makes it easier to view on a computer screen. Click the pictures on the left for a larger view.
The circuit diagram was drawn with Eagle Cad Light and if you want to experiment with this here are the files to open in Eagle Cad.
Download Phifact Eagle Cad Files
You can download Eagle Cad from their site and there is a free version for Windows, Linux and MAC
I’m no expert with Eagle Cad, or drawing circuit diagrams so if you produce a better version of the circuit diagram please let me know and I’ll be happy to post it here.