Sunday, October 27, 2013

BOM update - V0.1.1 design

This morning I posted up a parts list and Mouser BOM  (See Parts list tab above).   And there is some good news / bad news from a cost standpoint!

Good news is:  Basic component cost for the regulator came down a whopping $13.22 (to $29.72) through a combination of the simplified design and some more careful scrubbing of components selected.  The bad news is changing from the low-cost HC-05 Bluetooth module to the RN-41 eat up all that savings, and the new combined component costs (including optional Bluetooth module) now comes to $54.67, a $6 increase...

So why again did I switch out the Bluetooth module?  Two reasons:   First and foremost is the HC-05 has no FCC certification.  And given it also has no shielding there is a great probability this things is quit noisy from an EMI standpoint.   The RN-41 not only has the FCC cert (plus other countries as well), it also has the needed shielding.  

And there is another significant benefit of the RN-41, range.  The RN-41 is a full-power Bluetooth with a range of several 100 feet, which the HC-05 is a low-power class of Bluetooth modules, with a best range of maybe 100'.   Put it into a shielded engine room and that might get even shorter...  If you do not need the extra range you can swap-out for the RN-42, it too has the FCC cert, is pin and firmware compatible, but as a short-range lower power device is $7 lower in cost...

I have real mixed feeling over the Bluetooth module.  Perhaps once I finalize the design I will make up two PCBs - one for each - modify the firmware with some #defines and let you all decide which way you want to go.  

Off course, a 3rd option is:  Just built the board as it is today, but without the RN bluetooth.  Order the HC-05 from Ebay and use jumper wires to connect it via the service port!

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