Boron / Xenon / Argon Carrier for Outdoor Applications


#1

All, I will be creating a carrier board for the Boron to support outdoor use. Here are the main items I plan to include:

  • Temp sensor in case I need to control LiPo charging
  • External watchdog timer - connect to either Enable or !RST
  • Single - button on / off so you can leave the battery and power plugged in
  • The ability for the device to power-cycle itself
  • ESD and fuse protection
  • Headers for i2c, SPI and IO
  • Big capacitor on DC-IN to support Solar Powered use case

Please take a look. Comments are welcome. I will also be trying Cadlab.io to facilitate collaboration.

Here is a start of the layout, I also created a library for the Boron footprint on the carrier.

Thanks, Chip


#2

@chipmc, Nice work. You might want to add a photo of the physical board or some screenshots of the board layout so others can see what exactly this is without having to load up the brd and sch files. I kept clicking on your github profile pic thinking I’d see the carrier… that was a “doh” moment.


#3

@ninjatill,

Great point. Here is a board view from EAGLE. I also am uploading a picture of the current Electron carrier so you can see what I am going for.


Current Electron Board


Example of an outdoor sensor


Boron Carrier Rough Layout

Thanks,

Chip


#4

All,

Here is the first pass - will likely get a few of these made at OSHPark - unless someone has a good suggestion for an improvement!

Schematics:


Particle Device / Sensors / Headers
Power Management

Power protection
OSHPark Renders

Board View

This carrier should work for all Gen 3 devices. Please let me know what you think.

Thanks, Chip


#5

Since there is plenty of space, I would add a couple vias to avoid running traces under U2, R1 and R2. Also U7 pins 2,4.

What manages battery charging?


#6

@chipmc I like it! I think that @Pescatore has a good point about the vias. Also, if you haven’t yet, you might want to check out JLCPCB for board manufacturing. I’ve used them for multiple boards now and they are great. Then you can also order some of your components from LCSC which are normally 1/3 of the cost that you find from your go to US distributors.

Normally about 1 week for me to get new boards from time of order.


#7

@Pescatore,

Thanks and very good point. For some reason (likely my inner type A personality) I try to minimize vias but it would help with clearance.

The charging for the LiPo batter is managed by the charge circuit on the Gen3 device. - the BQ24195.
46%20AM

Thanks, Chip


#8

Thank you for the suggestion.


#9

Have you noticed any issues when connecting a solar panel to the BQ24195?

I am attempting to charge an Argon and Xenon but those have a XC6802 for the LiPo charging.


#10

I see that you use copper pours on both top and bottom planes… that’s a common practice. Are both pours tied to ground? Or is one pour +V and the other side is GND? If they are both GND planes, then you should “stitch” the ground planes together to ensure no pour areas float. It makes for a stronger ground. If you have a signal trace that you want to guard against interference, then you can “stitch” along either side of the trace (placing many vias parallel to the trace.)

In EE 101, many years ago, the professor gave us a challenge to place as few vias on the board as possible. But that was because we were etching our own board and in general, it is best to avoid vias in your signal traces if possible. But with today’s automation, there’s no reason to hold back on “necessary” vias such as plane stitching (unless the PCB fab house charges more if you put more vias per sq inch than they allow for free). I still try to minimize my signal vias and I can do better than the autorouter in many cases.


#11

@roofTip,

No, I have over 50 Particle Electrons deployed and almost all of them are running on Solar Power. I was very happy to hear that this part was going to be used in the Gen 3 Hardware. See @RWB’s great tips on how to manage the PMIC.

Thanks, Chip


#12

@ninjatill,

Thank you and, yes, both sides have ground pours. Notice, I have put vias around many of the ground pads to help make for a better connection. That said, I have noticed that many professional boards - especially multi-layer boards (see the antenna section of the Boron for example) put a great number of vias on either side of the antenna trace. Perhaps this is something I could do more of. As you alluded to, vas do not increase the cost of the board. I will take another look to see if there are disconnected areas of the ground pour on the board.

Thank you for taking a look.

Thanks, Chip


#13

Since you are using ground pours, recommend making sure you have thermals on any ground pads that you expect to solder to.

In the spirit of improving manufacturability, especially small quantity manual soldering, I would recommend you extend the advice on removing traced running through the center of SMT parts throughout the board.


#14

@AndyW,

Good point, I do have thermals on and have included an image below for folks on the forum who may not be familiar with the term (hint: look at the GND pins - Thermals control the amount of copper that connect the pad under that pin with the larger sound “pour” to improve the heat profile in a reflow oven).

I had not appreciated the “not routing through the center of SMT parts” issue until today. I always learn something when I ask the community for input.

Thank you for your advice.

Chip


#15

Agreed, routing traces through SMT parts is not an issue for professional assembly, all that matters is meeting the design rules for the board house. For something that may be hand assembled by a hobbyist, its good to be far more cautious - and you’ve got room to burn on this board.


#16

Another thought: The I/O A0/A1 etc on the multi pin headers may be more useful if you turn each one into a “Grove” style connection i.e. use a 3pin header with sig-5V-0V with each I/O on the sig pin. This can be made into a parallel strip of 3 headers (x how ever many I/O’s wide).

What this does is allow a new sensor to be easily connected (be it analog, digital or One wire) without having to customise a harness from JP8 or JP1. This makes it trivial to add/remove a new sensor in the field without any tooling required.

Additionally add a 3V3 & GND pin to the RX/TX JP3 so again it makes it easy to plug into a level shifter for connection to an external RS232 device.

If you reconfigure the SDA/SCL connector to suit this layout of the connector pins (https://store.ncd.io/product/soil-moisture-sensor-analog-digital/ - click on Resources tab at bottom of page) you suddenly open up the board to a huge number of sensor modules from NCD.IO and others that can be easily connected (and extended) to make the carrier board very flexible and configurable for a multitude of different applications


#17

@shanevanj,

I like your idea about using standard connectors. However, the NCD standard is defined on the site as strictly 5V.

NCD is the creator of plug and play modular hardware using the NCD I2C Interface connector standard. NCD I2C devices allow you to chain together several devices on the I2C bus, and communicate to each device individually at high speed (subject to the limitations of I2C). The NCD I2C Interface uses a standard 4-Pin I2C Input and I2C Output connector. NCD I2C devices communicate 5V I2C data and provides 5V DC power through this connector. NCD I2C devices use standard I2C communications for all data transport, which is supported by nearly every microcontroller in production today. The NCD I2C Interface is strictly a 5V standard, which is ideal for transport across longer cables. NCD I2C devices always include a 6″ (152mm) 4-conductor I2C cable. NCD I2C Mini Modules always include a 3″ (76mm) 4-conductor I2C cable. Cables and connectors are available separately for designers who would like to include their own NCD I2C Interface into their designs.

Perhaps the “Grove” connector standard - would be more applicable since it supports 3.3V devices. It appears this will also work for Adafruit STEMMA - though the pins are reversed.

Thank you for the suggestion.

Chip


#18

Yes, I like 5V currently as there are seemingly more 5V of the shelf modules and peripherals out there today. I am also doing a similar basebord/carrier for mesh boards - more leaning towards commercial/industrial usage. So it has an RTC, ETH, PoE, 12VDC - fits into a standard DIN rail enclosure with 3 external 5V digital (and one-wire) i/o, as well as a 5V I2C and a spdt relay. Display is a 0,96" I2C display. I would plan to use selected NCD mini modules for expansion out the I2C port hence my leaning towards this approach. I am happy to help you review you board as you progress.

Cheers Shane


#19

Thank you Chip for sharing your work and ideas, yet again!
I enjoy a lot these topics.
Gustavo.


#20

Hi Chip. 12V DC power input capability please. Opens up a wide range of marine and auto capabilities. Cheers