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Messages - SkyLabs

2
Project logs / Location Based Development Board
All,

Courtesy of Dangerous Prototypes Dirty PCB service, I have been able to put together and complete the testing of the first prototype of my very own location based development board. Here's a bit of a glamour shot below.



So lets talk about what you’re looking at. The board is a 4 layer PCB of dimensions 50 x 68 mm. The populated board has a maximum thickness of 9 mm. I considered using a 2 layer board, but the ground planes would not have been large enough and the substrate was too thick for the micro strip trace to the antenna to be of a realistic width.  The microcontroller is running an Arduino Bootloader and the board is pictured on 7mm standoffs that are attached using M2 screws. Below is a photo of the assembled device and an overview of the hardware on board.

On the topside of the PCB, Image attached, working top to bottom, the device consists of:

    Penta-band GPRS/GSM/EDGE/HSPA/CDMA Antenna
    Antenna Matching Circuit
    Micro SIM Card Holder
    uBlox SARA-G350 GSM/GPRS Module (2.5G)
    Netwok Status Indication LED
    Standard Arduino LED
    Micro SD Card Holder
    uBlox CAM-M8Q GPS Module & Embedded Antenna
    Mini-B USB Connector
    F234XD USB-UART Controller
    Voltage Regulation
    Li-Po Battery Charging Controller via USB
    JST Connector for Battery

On the bottom of the PCB, Image attached, working top to bottom, the device consists of:

    Additional Voltage Regulation
    3x Expansion Ports that use FFC Ribbon Cables
    ATMega2560AU Microcontroller
    Logic Level Converter

The board acts like any other Arduino, building upon that easy to use and powerful framework that is particularly inviting for new users. Too commonly I see pictures of people who have created complex circuits involving GPS Modules, SD  Cards or GPRS Modules ect and they all have one thing in common. They are either very messy and fragile with wires running everywhere, often consisting of large areas of breadboard, and they are bulky. An Arduino Mega and a shield or two in terms of electronics is gigantic, far from pocket sized. This to me feels pretty nifty in terms of size, and what you can do with it.

So with the overview complete, I thought I’d move onto some of the things I have been able to undertake with the device. The firmware I have running on the device currently takes in the GPS data from the serial UART, processes it on board, establishes a GPRS connection, and then carries out a GET Request over HTTP to place that GPRMC data into a mySQL database using a PHP script. I can then log onto an online application and view the location of the device in real time. Furthermore this device will carry out this task anywhere in the world with a cellular connection. This is a much more attractive method than Wi-Fi or Bluetooth where range becomes an issue. The location is displayed using google maps, as shown in the application screenshot below. The device runs off a data only M2M Sim that costa about 45p a month prepaid for 2Mb of data which is plenty for just GPS data.



So that's what I've been able to do so far and really I was just looking to get a little feedback from the community on the project. When I feel it's ready, I'd love to release all the design files. I've got a few things in the works using the expansion boards and so I'll post that when it's done but I'm really looking forward to getting a feel for what you think of the project.

Thanks.
4
Project development, ideas, and suggestions / Re: Dirty PCB Panelization
I managed to snap up both the cables and connectors from Digikey. The cables are Molex and the connectors are FCI, they have plenty in stock. There is actually a company I can across in based in china that makes FFC cables based on a drawing, but obviously there looking for bulk orders.

Also, does anybody know where to find the 4 layer Eagle DRU for Dirty PCB's?
5
Project development, ideas, and suggestions / Re: Dirty PCB Panelization
To be honest as Ian said, at these prices as long as I can combine them together on one board I'm happy. I will probably set the holes back a bit more, snap them with pliers and then just file off the remainder of the tab. I can see this would be a pain for a larger run, but I'm only going to assemble two of each design so it's no hassle.
6
Project development, ideas, and suggestions / Dirty PCB Panelization
Hey,

I was reading up on the Dirty PCB service but I am unclear on a few things regarding panellization, and what it actually means.

I have attached an image of a design which constitutes a group of 2 layer circuits joined together onto one board using breakaway tabs in a 5cm x 5cm foot print.

Put simply I want to know if this is allowed, or if it will be rejected down the line for some reason - can't see why but the website left me confused and I want to get it straight before I order.

Thanks in advance,

Matt

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