Now we need to consider mounting the project in a case. Your best bet is a case that is not too deep to allow easy access, and lay everything out with a bit of room around them. Remember that the Arduino has a shield on top of it, and perhaps the RTC is standing vertically, adding to its height. The Arduino should be mounted on little feet called standoffs. A screw holds the Arduino to the standoff, and another screw from the back of the case will hold the standoff to the case, as shown in Figure 8-32.
Always plan for a bigger case than you think you’ll need. Don’t forget the power supplies and connectors, and remember that wires take up space as well. You want to route the wires between the boards and not over the boards so they don’t interfere if you have to work on or remove anything. For tidy wiring, I like these self-adhesive mounts for cable ties, as shown in Figure 8-33.
For projects with multiple power supplies, as we have here, consider mounting a small outlet strip inside the case. Use a strong double-sided tape to mount the outlet strip. If both your power supplies have only two prongs, you can use a two-pronged extension with at least two outlets instead of a larger three-pronged outlet strip.
This means another revision to our shopping list (we’re now at revision 0.6):
- Case
- Standoffs
- Mounting screws and/or nuts
- Cable ties
- Adhesive cable-tie mounts (available from Jameco)
- Strong double-sided tape (e.g., Digi-Key part number 3539-B831141-ND)
- Outlet strip
I like to keep the power supplies away from the Arduino. You should mount the Arduino near the bottom so that the wires from the valves and the DHT11 sensor can enter from the bottom, but not too close. You’ll be happy to have room for your hands and a screwdriver when attaching wires to the screw terminals, or if you need to work on the Arduino.
The USB cable can come out of any side.
You should always try to route the wires in straight lines and in tidy bundles. This makes working on the project later so much easier.
In this figure I’ve left many components off the Proto Shield to make it easier to see how things are connected. I’ve shown one cable tie, but you should use as many cable ties as you need to keep the wiring organized and tidy. Always use a cable tie before a wire leaves the enclosure; this serves as strain reliever in case the cable gets tugged: it will stress the cable-tie mount, and not your delicate circuitry.
As before, pay careful attention to the polarity of the water valve power supply, if it’s a DC system.
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