Today I’m going to focus on the layout of the Grow Chamber’s sensor puck.  I discussed the sensor puck schematic in an earlier post.  Before I get to the layout, I need to pick a connector to use for the pin outs.  Urgh…connectors…it is hard for me to get my head around connectors…so many choices…picking the “right one” is a task I don’t always succeed at.

 

Open Source

The footprints I added to the sensor puck cvpcb are locked at this GitHub location.

Adding The Connector

The PCB needs a 1 x 7 connector:

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onto cvpcb…check this out… a slew of errors saying the component libraries can’t be found:

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bummer….but – as is pretty much true in every case – I am not the only one.  I did what Brandon did and issue solved: For record, in cvpcb I went to Preferences –> Footprint Libraries. Removed all Global libraries then used Append with Wizard to add all GitHub libraries and saved them locally on my machine.  

I like to use 0805 size for jellybean parts.  Here’s what cvpcb looks like before I have created footprints for the other parts:

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I decided to keep the connector simple and use the same type of connector used on Arduino shields.  Spark fun has a nice tutorial on connectors.  I’m using the connector discussed under the topic “Pin Head Connectors.”

 

 As noted in the Sparkfun post: The most commonly seen pin headers are .1″ single or double row connectors. These come in male and female versions, and are the connectors used to connect Arduino boards and shields together. 

.1” is the pitch I will use.

Perhaps there is a 7 pos footprint for an Arduino header like connector within the wad of footprints that come with Kicad.  I’m thinking it will take less time for me to make my own.  I’ll use this Arduino header data sheet for reference. 

I put the footprints I added into TheLeafSpa.pretty library at this GitHub location.

The Thermistor

On second thought, the 0402N sized Thermistor noted in the app note’s BoM I discussed here is uncomfortably small for my soldering skills.  I like working with 0805s (I also like reading with larger fonts…).  I went back to a post I wrote where I evolved my knowledge of how thermistors work (and now seem to have forgotten)…and decided I was making too big a deal about matching (B parameter) specs.  Also – didn’t I say I wasn’t even going to be using this feature?  So I’m changing the thermistor to an 0805 100KΩ (Digikey link).

Additional Footprints

I made footprints for the CCS811 and the Si7006.  These have been added to TheLeafSpa.pretty library located at this GitHub location.

I’m ready to do the layout…but before I do that…

Generating the BoM

I want to generate the BoM to make sure I get all the parts I need.  I’ll be using MakeDigikeyBOM.py which I discussed in several posts – including this one.  Steps:

  • run bom2csv (discussed in this post) to create.  This creates the GrowChamberSensorPuck.csv file (GitHub location).
  • download a csv file of jellybean parts.  The jellybean parts Google Spreadsheet is located here.  The downloaded csv file is located at this GitHub location.
  • Make sure the MakeDigikeyBOM .py files are available to run.  The GitHub location for MakeDigikeyBOM is here
…I ran out of time for today…. tomorrow I make progress on sensing and monitoring the Grow Chamber.  Then I will get back to BOM generation and layout.

 

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