Adafruit’s Circuit Playground is an awesome prototyping board that can be connected to a range of sensors and can be coded to take input and provide feedback in fun ways.
The pins provide some pretty large holes that are designed to be easy to use with alligator clips and the circular nature makes it hard for the clips to cross over unlike regular pinholes. Soldering is another option for creating a more compact form-factor. However with holes this large, we can do some interesting things.
You might want to be conservative with your projects and reuse the board a bunch of different ways. Soldering, unsoldering and re-soldering a board is no fun especially for a novice. We discovered this cool technique to wrap the wire around the holes:
- To start with, solder solid wires to the sensor itself.
- Cut the wires about twice the length necessary to get to the opposing hole.
- Pass the full length of the wire unstripped through the hole.
- Using a wire stripper, strip all possible wire that protrudes from the other side.
Doing it in segments will make it easy.
- Then simply twirl the wire around and back through the hole as many times as possible to create a tight grip. I used needle-nosed pliers and made sure it was snug all the way through.
Voila, you have a very solid connection to your sensor without the permanency of soldering the actual board and leaving it open to experiment with an endless number of ways. This solution would be great in a classroom environment where you may want to reuse the actual boards but don’t necessarily want the thing tethered to a clunky breadboard.
Corrosion of sensors is something to consider when deploying a project in the field. Solutions range from high-tech, such as specialized gold plating, to low-tech, such as coating the sensors cheaply using paint.
The main tradeoffs are cost vs. precision. Often high-end, expensive sensors are housed in the same low-grade stainless steel as much cheaper sensors tend to use. The only way to really tell is trial and error. A cheap temperature probe coated in paint and properly calibrated can often provide the same output as a sensor costing many times as much. In this scenario, you may be better off with going the low-tech route and routinely maintaining and swapping out degrading sensors.
For soil sensor monitors, a different technique is required since coating the sensors would impede the conductivity that is measured by the sensor. One key measure to extend the life of the sensor is to provide power to the sensor only when measuring the conductivity. Depending on how frequently the moisture is measured, this should increase the lifetime of the sensor much more than constantly providing power.
Another tip is when wiring the sensor to your device, use ones that attach via a 3 pin terminal to allow you to switch them out easily when needed during a maintenance cycle. Going a more expensive route may not be the best solution in this case and just as your plants need regular maintenance, so too will your sensors in a corrosive environment.
During our project, we came across a new challenge… How to cut through plastic boxes. We came up with different solutions. One of the solutions, a low-cost solution is to get a soldering iron and a very sharp blade. By attaching the blade to the soldering iron with conductive wires you get a plastic cutting knife. We used wires to make sure that the blade didn’t move at all.
Another low-cost solution was to attach a wire that transfers heat to the soldering iron. With heat-resistant gloves, hold on to the other end of the wire and just grind through the plastic.
Although low-cost solutions are cheap, they are not always optimal to get the results you need. The next solution is to buy a Dremel. The best accessories to use with the Dremel is the grinder and the cutting kit. I wouldn’t recommend the other accessories since we accidentally destroyed one of our boxes using them. This solution is a bit costly but will get the job done very well.
A neat technique to get low gauge stranded wires affordably is to pick up some of these ribbon cables at your local electronics shop:
Simply separate the wires with your fingernails and strip them with with a 28 gauge wire stripper. The exact gauge is usually printed right on the ribbon cable (in this case, 28 AWG).
No fancy colours but these are a great help at fitting your electronics into tight enclosures.