My own redesign

[jazzjunkie]

Never one to leave well enough alone, I’ve gone and made my own version of OpenSprinkler Pi to better suit my own needs.

This was done with a few goals in mind:
1) Reduce the PCB dimensions, and tailor screw holes to match my own RasPi B.
2) Mount the board directly on top of the Raspberry Pi without ribbon cables.
3) Remove the expansion header (I only have six irrigation zones, so just to save space).
4) Tweak the BOM to include components I already have on-hand.
5) Satisfy my own compulsive need to mess around with absolutely everything.

The working draft measures 2.1″ x 3.375″ inches instead of 3.5″ x 4″.
There’s no PCF8591T, but I think I can squeeze one in without adding too much board space.

Soon, I’d also like to accomodate mounting a small automotive rear-camera monitor for easy status monitoring.

Attached is a PNG showing the working layout only; the schematic is (basically the same as OpenSprinkler Pi V1.1).
Not displays, are the GND pours on top and bottom layers.

If anybody’s interested, I will share the design files.

[djagerif]

Nice work!!

I would love to do this as well, just to add a Rain Sensor for one 🙂

[Ray]

Very nice work. Glad that OSPi inspired you to design your own board. A few quick comments:
– The COM (common) port just needs one pin. The reason I have two (which are connected together) is to re-use the 2p terminal block so to reduce the total number of different parts. You can get rid of one to save some space.
– Regarding PCF8591, you can easily replace it with an ADC chip of much smaller package, such as MCP3021, which provides one ADC channel and takes almost no space.
– If you want to add a rain sensor port with minimal impact to the board size, you may want to take a look at the microcontroller-based OpenSprinkler:
http://rayshobby.net/wordpress/wp-content/uploads/2013/06/os20_component_diagram-1024×599.jpg
where the rain sensor port is the blue-colors screw terminal located in the interior of the PCB.

[jazzjunkie]

Thanks for the feedback!

Using two COM pins still makes sense to me; fitting six wires into a single screw terminal could be a real pain.
The outline fits the RasPi fairly snugly, so my size goal is pretty much met. I’m not too worried about the space taken up by that extra COM terminal.

Assuming a good internet connection, rainfall/humidity/temperature information can come from a local weather station. An analog channel could be used to detect open circuits on the outputs (a single ADC channel should be enough, monitoring a sense resistor on the COM terminals).

A few more ideas for additional features:
1) Interface circuit for an electronic flow sensor. Many deliver one pulse per volume unit of water – if I can’t find a counter with I2C or SPI, an ATtiny would do the job.
2) Indicator LEDs for each channel. Space is especially tight around there, so it might not be very practical.

[Vaughano]

I did a little experiment with flow meter pulse counting, see viewtopic.php?f=22&t=125#p605 for some discussion and some C code.

[djagerif]

How about extending the Rpi header and add the following for your Zone Indicator requirement?

http://www.hobbytronics.co.uk/raspberry-pi/tft-serial-display-18

[txheat]

jazzjunkie, Please share!

[jazzjunkie]

Here are links to the draft .brd and .sch files stored on my google drive.

https://docs.google.com/file/d/0B9XWqgRqzxl6V1NLcGhmSU0tNWc/edit?usp=sharing
https://docs.google.com/file/d/0B9XWqgRqzxl6SWU2VE5iRG5XVDQ/edit?usp=sharing

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