Wireless intercom V3 Prototype done
I completed assembly of the basic prototypes for version 3 of the wireless intercom:
I placed the battery holders on the outside for two primary reasons:
The boxes are different sizes because that is what I had on hand. I like the thinner, longer one better, but neither of them are really the correct form factor. Ideally I'll end up with a box about 4" x 2" x 1" (100mm x 50mm x 25mm), including the batteries.
Current consumption is between 63mA and 68mA. AAA size batteries should last over 10 hours of intermittent use. I'll have to conduct testing to find out the capacity of AAA batteries under a constant draw of 70mA. AAA NIMH cells come in 700mAH to 1000mAH pretty inexpensively as well, so I can count on 10 hour operating time (or longer) for rechargables now. Another option is the 860mAH Li-ION cell. It's about the same size as a AAA 3 cell battery pack in length and width, but only 5mm thick (just under 1/4"). There's a charging IC for it that requires very few external components and accepts power from two sources for charging and device operation. It's an expensive option, adding about $15 total to the device cost, but being much smaller and lighter it has advantages.
So I've completed the primary goal of this prototype - making a set that is usable off the bench for power consumption, distance and quality testing. It doesn't have external volume or channel controls, though, which is something I plan on featuring in the completed design. I haven't yet decided whether I'm going to include external audio sources in the final feature set - the month is almost half over and I need to move on to the next project next month.
Next week I expect I'll be working on the PCB design, and the final week I'll be assembling and testing the final units.
As always, if you have any questions or comments, please leave feedback.