Major PCB changes, parts, and 3D models

A project log for GPS Receiver for Nikon D3100 Cameras

An inexpensive and more accurate GPS receiver accessory for Nikon D3100 (and compatible) cameras.

KevinKevin 09/27/2015 at 20:350 Comments

In my last log file I said I the PCB work is almost complete. Um... wrong! That was when I was on revision 4 of the PCB. I'm now on revision 11.

About a week ago I received the right angle pushbuttons I had ordered. With the pushbutton in hand I created a 3D model of it for use with Kicad. When I added the model to the board I saw a problem. The switch was wider then expected so there was barely enough room for it. I swapped the pushbutton and slide switches (and voltage regulation parts), and widened the board to 1.75" to make a bit more room for the parts across the front of the PCB.

I've searched for sync cables and found ones with a mini USB connector but none that used micro USB. This resulted in more PCB changes. The mini connector is wider than the micro so I would have had to widen the board by almost 0.1". By rotating P4 I was able to slide the mini USB in behind the pushbutton and avoided changing the size of the PCB. Having rotated P4 I decided to rotate IC1. I also changed the LED to a 3mm one as I felt the 5mm was too big compared to the 3.4mm diameter handle of the pushbutton right next to it. These two changes allowed me to shrink the PCB to 1.5" x 1" and it only has a single via.

I have moved or redone all of the traces on the board several times but I think (I hope) that it is in a final state ready to be sent out to be manufactured. I have ordered all the remaining parts (USB mini connectors, slide switch, 3mm LEDs, and tantalum caps) needed for this project. Some of the parts were already in my parts bins but I will soon have enough parts to make more than one prototype. Once all the parts have arrived (it may be a month for some to arrive) I will do a final check of the PCB footprints before sending the board out to be made.

I have updated the parts list for this project. One change was from a 5mm LED to a 3mm super bright one. It will allow me to reduce the current needed to drive the LED while still being bright enough to be visible when the device is used outdoors. I have made a note to see if can add a software option to offer variable brightness of the LED. When used indoors the user may want to reduce the LED brightness and further reducing current requirements.

The last 3D models I need to make are for the top part of the camera and for the final enclosure. I need to check clearances between my devices enclosure and the cameras built-in flash unit as I don't want to interfere with the operation of the built-in flash. I still need to work out how to mount the GPS antenna in the enclosure and how I'm going to stabilize the end of the GPS module to minimize movement and vibration. Once the models are done the only remaining task is to finish the software. I will keep it simple at first by just having it calculate moving averages of the GPS data and handle the baud rate conversion.