Just started working with Uno and Mega, have a farm and needed some automation for more than just sprinklers. Need the ability to monitor over time, pressure, temp, weather, soil, samples over long periods, as well as run complex 88 zone irrigation, nutrient injection, security, lighting, and multiple RF/APRS related systems for farm management.
While Ard’s are small they are quite useful when used for these applications. 74hc595s, triac handle 24VAC controls, I2C, SPI cover weather, temp, pressure, mechanical limit or load sensors.
The core however needed a basic monitoring component so we started there. There were several designs in the web for basic display, buttons and things, but needed quite a bit more capability. We initially started with Uno and Seead color touch TFT 2.0, found it was out of IO, not enough memory, and the Seead touch sensors were piss poor and unusable, then display however was not too bad. We upgraded to Mega and then had enough IO to minimize external components, added 4x4 keypad 0-9, *,#, A-D then designed custom font for horizontal display, added to libraries horizontal display routines for graphing, positioning text, and painting backing store horizontally. These were modifications of the Seead libraries which are missing significant functionality out of the box.
The original scope design http://n.mtng.org/ele/arduino/oscillo.html was black and white, Much smaller display so significant work was done to expand the design and replace the voltage divider keypad with reliable 4x4 keypad. The VD keypad relied on fixed voltage references that varied between boards, standard 4x4 keypad eliminated this. Ard’s are slow babys but if you restrict the time domain to the application domain 20ms-1000hrs (with SD store) works well, drop usual voltage divider and protection network to the front end with analog sw matrix to switch between things to be sampled you have very useful tool to gain information on the real time and longer term state of these complex farming systems. One of the key things missing in farming systems is the ability to measure inputs, usually most are output only, or just have rain sensor port. Ard’s change this radically. Add wireless and you eliminate most of the wiring and also run solar or local power. Saves big $ over wired systems. 2 wireless routers gives solid coverage for 40 acres and 64 or more sub systems with 64 or more sensors and triac or relays. Pretty cool stuff.
See my Facebook site for images of the project https://www.facebook.com/photo.php?fbid=737918649552563&set=a.100272063317228.413.100000033031519&type=1&theater¬if_t=like
Will be redesigning the keypad to add better workflow, over next couple of days.
Have Uno setup with SPI as slave now with 32 valve triac array, 70 AMP 240VAC PWM motor controller, pressure sensors will move this to Mega later this week.
So not bad start so far. Learning lots of interesting things. Soon as snow leaves however have to get back to farming.