The Creek: Creek Board 1.1

In the previous post I described the entire system architecture.  In this post, I am going to describe the Arduino shield that I unfortunately call “Elkhorn Creek Water Level 1.1”.  It is unfortunate because in version 1.0 I made a really stupid error which ruined the first run of printed circuit boards.  You can read more about how I made the error and what I am doing in the future in the post Creek Board 1.0 RCCA.

To make this system work I need to be able to interface the PSoC4200 with two sensors:

• The US381-000005-015PG pressure sensor
• A TMP036 temperature sensor

Both of these sensors are subject to environmental noise so they both have capacitive or RC filters connected to them.  I originally built a prototype of this board using a proto board.  However, it was a PITA because the wires would come loose and the system would stop working.

So I decided to make a real PCB.  To do the design, I used the Eagle 7.2 PCB editor as it seemed like it had the most support from the maker community.  The schematic for the system is fairly simple.  It has

• Pressure Sensor
  • X1: A Molex Microfit 3.0 Connector to attach the two wires from the pressure sensor
  • R1: A 51.1 Ohm resistor to group to convert the 4-20mA –>  0.204mV to 1.022V
  • C1/R2: A low pass filter
  • TVS1: A ESD diode to clamp any ESD event to ground to prevent it from blowing up the PSoC4A or the Sensor
• Temperature Sensor
  • TMP36: A sensor that turns temperature into a voltage.  The equation for temperature is T=0.5V+10mV/degreeC.  For 25 degrees C the Voltage = 750mV
  • C2 + C3: Two decoupling capacitors to filter power supply noise
• Arduino Interface
  • A standard Arduino interface set of pins + the additional Cypress CY8CKIT-042 pins.  I only used the A0 and A1 pins for signals and the Vin pin (which is 12v) to drive the current loop
• Measurement Test Points
  • Keystone 5000 test points.  These test points are a little loop of wire that sticks up from the surface of the PCB to make  it easy to probe a voltage with your DMM.  

Here is the final Eagle Schematic for the board.

And the layout:

Once I completed the layout I sent the board to OSH Park to be manufactured.  I have shared the project on their website.  OSH Park is an excellent company that is easy to do business with.  They charged me $22.55 for three of the boards.  The fit and finish of the boards is very nice.  Here is the board:

Here is the assembled board:

 

I have posted all of the project files at github.  You can “git” them from https://github.com/iotexpert/TheCreek  The Eagle project is in the CreekBoard directory.