I’ve already covered the outputs required from the Phidgets Controller in previous articles. But you can’t forget the inputs. While the Honey Stick machine could be setup to simply run on timings when to do what, and assume that each task is done correctly, it would be prone to problems if anything varried. Even differences in the thickness or temperature of the honey would cause problems. Thus I intend to include quite a few input sensors to make the machine smart enough to adapt to most situations. These inputs will include:
- Temperature of the straw sealing heating elements. Temperature when melting the plastic ends is critical to getting a good seal. Too low a temperature won’t seal the straw, and too high will melt though and leave a hole. While this could be controlled by a simple thermostat, it’s easier to adjust on the fly if the computer knows what the temperature is. Plus, sine the Phidget’s USB interface has plenty of inputs, it costs a fraction of the amount that a dedicated controller would cost.
- Temperature of the honey. My honey stick machine will include a heater for the honey (or other syrup) to keep it flowing well. We don’t want to overheat or even pasterize the honey (my customers perfer raw honey), but it flows much better at 90 degrees than at room temperature (which may only be in the 60s at my house in the winter). It may also give the computer an idea of how fast the honey should be flowing so as to adjust timing of filling cycle.
- IR Emitter and Detector pairs. These will basically function like the safey eye on your garage door. When the beam is broken, something is in the way. In this case it will either be a straw or honey. We will have 4 such pairs to determin if there are straw in the bin, in the filler holder, if there is honey in the feed line (or if we have run out of honey), and if the honey has filled the straw. I expect the positioning of this last sensor to be critical to get repeatability without having to clean the heating elements constantly. Too much honey in the straw and the honey will leak out everywhere, too little and it will leave air bubles and burn though the straw. (Less time/heat is required to seal an empty straw vs. a straw with honey at the sealing location)
- Current Sensor to determine if the pump is running. This wouldn’t seem necessary as the computer is telling the pump when to turn on, but the pump we have chosen has overrides that may cause it to turn off without the computers knowlege. Thus I think it would be usefull to have this additional input. It may prove to be unnecessary in actual use (the pump may never turn off on it’s own), but I will include this circuit in the prototype.
That pretty much fills up all 8 of the Phidgets analog inputs, and fortunately I can’t think of anything else I need to monitor at this point. I will take advantage of several of the Phidget’s digital inputs as well to add features like a ‘kill switch’, power switch, start button, etc. so that it could basically be run without looking at the computer screen (once all the bugs get worked out). The Phidget’s also has 8 of these digital on/off inputs, more than I can think of a use for right now.
Status Update: I have ordered and received most of the electronics parts that I think I’ll need. I’ll begin wireing and testing circuits possibly later this week if time allows. I do plan on building them in modules and not just one big circuit so that it will be relatively easy to adjust for the final machine.