Home > Tech geeks > I Don’t Know Jack

I Don’t Know Jack

…about wireless antenna design. That’s what I have come to realize. After placing that antenna spiral on the PCB, I decided it might be prudent to Google the subject matter of wireless antennas, and found this paper. Basically, the spiral probably wouldn’t have hurt anything, but its damn near worthless too. As a result, I ripped that trace off the main board design and instead put in a couple of pads to hook in a wire antenna, if I find it necessary. A question to the PICAXE Forum has somewhat alleviated my fears that the pump motors won’t distort the signal when they turn on and off, but I’ll have to do some real-time testing and see. Wireless may be a bust for this application… at least for now.

One upgrade I really must consider for the next iteration will be using the XBee hardware set. It operates at 2.4Ghz and is bi-directional, and appears to still be reasonably priced (as far as this stuff goes)… These chips come off-the-shelf with nice features like individual addressing and error checking built in. That would allow me to have multiple individual wireless transmitters in the grant, pump skid control box, main sculpture control box, and at the PC all working together – Wow. What a vision that is… Maybe just a pipe dream?

Getting back to the board, I also tweaked a few additional aspects of the design:

(1) I realized my 330, 10k and 22k resistor values got re-labled as 4K7 somewhere along the line, most likely the result of a poorly executed multi-select change. I would have soldered in the correct values, but the PCB artwork would have been wrong… Also could be confusing to anyone looking at the board design (not as if many will do that anyways)

(2) I put additional silkscreen layer descriptions on the +5V and GND rail pads

(3) I completely hid the unused pins for the ULN2803A Darlington driver rather than just moving them to the top layer. As I said before, I’m clipping those leads off the IC socket anyways… Why show them at all?

(4) I put in a slot for a .2″ pitch terminal connector over by the power supply. Before I solder that $16 fancy power supply and $3 fuse holder to the board, I’m going to first test it out using batteries. If there is a circuit problem, it will be safer for the components on the board if less juice is flowing through them. I’d rather hose a few batteries than have the power supply go BOOM and take the other stuff with it. Once the circuit is tested out and I begin using the VAA505 to power the circuit, those screw terminals could be used to power other 5V loads or whatever…

(5) Minor trace movements to provide more clearance, clean up ugliness, etc.

I am dying to pull the trigger and just make this happen… WHERE IS MY DRILL PRESS?!!?!? The sooner it gets here, the sooner I can etch, drill and solder my boards up… and the sooner I can start actually use this grant I’ve been designing for several months. Patience is starting to wear a little thin…

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