Battery and nRF24L01 connections and definitions in Eagle

Question

Hello,

I am designing a board that has 4 sensors and an nRF24L01 wireless module to send the sensor readings off to a base station. It's quite similar to maniacbug's Low Power Sensor project. I'm doing a thru-hole design.

I'm a new Eagle user, but think I am coming up to speed pretty reasonably with some of the very good tutorials on YouTube and looking at other projects for examples. I have a few random questions.

1. For powering my project, I am thinking of using 2 AAA or 2 AA batteries, putting them in a separate holder and just soldering power leads to the board. So in Eagle schematic, how would I define these solder points in the schematic and the board layout?

2. The nRF24L01 wireless module that I have is a separate breakout board that has a block of 2x4 long, square header pins. Hopefully you can see the image below. What is the best way to connect this to the main board? Pins look a bit big to solder. I've looked around at female sockets to mount on the main board, but I'm not convinced I have found the right solution. Any suggestions?

Thanks for any suggestions,

Steve

autodeskguest · Answer

On 02/08/2015 09:14 PM, Steve McCrew wrote:

Hello,

I am designing a board that has 4 sensors and an nRF24L01 wireless
module to send the sensor readings off to a base station. It's quite
similar to maniacbug's Low Power Sensor
(https://maniacbug.wordpress.com/2011/10/19/sensor-node/) project. I'm
doing a thru-hole design.

I'm a new Eagle user, but think I am coming up to speed pretty
reasonably with some of the very good tutorials on YouTube and looking
at other projects for examples. I have a few random questions.

1. For powering my project, I am thinking of using 2 AAA or 2 AA
batteries, putting them in a separate holder and just soldering power
leads to the board. So in Eagle schematic, how would I define these
solder points in the schematic and the board layout?

2. The nRF24L01 wireless module that I have is a separate breakout
board that has a block of 2x4 long, square header pins. Hopefully you
can see the image below. What is the best way to connect this to the
main board? Pins look a bit big to solder. I've looked around at
female sockets to mount on the main board, but I'm not convinced I have
found the right solution. Any suggestions?

To provide pads for connecting your battery holder, you might want to

look at the "PINHD-1x1" or "PINHD-1x2" devices in the "pinhead" library.

They're intended for use with pin header strips, but they'd probably

work with the wires on your battery holder. Check the diameter of the

wire vs the finished diameter of the hole.

I built something very similar a while back, also using the nRF24L01+

module. You can get female sockets that will accept a pin header like

that on the module, but unless you absolutely have to be able to remove

the module you'd probably be better off using a PINHD-2x4 device to lay

out your board. After inserting the module pins through your PCB, clip

them off short before soldering them in place.

Bear in mind that the PCB traces on the module on the other end from the

connector forms an antenna. It won't behave properly if you mount

components, route traces, or place a ground plane under it. Best to let

about half the module extend beyond the end of your PCB, or at worst

have a large area of totally bare board (no components, no copper) near it.

Another thought is to watch the discharge curves for standard Alkaline

batteries. They start above the nominal 1.5V, then head south at a

pretty fair clip. At full discharge they put out barely 0.9V each. The

nRF24L01+ is rated from 3.6V to 1.9V, but the microprocessor you use may

not be happy. I used a PIC 16LF876 in my initial design because it's

rated to run down to 2.0V.

-Reece