Under Pressure
Sunday, June 10th, 2007…So this weekend I finally got around to doing something that I have been meaning to for some time - Building a test rig for the MPX5010GSX pressure sensors. You guys have already seen my temperature sensor test rigs in previous posts like Electromadness Continues, and I’ve had the pressure sensors for a while but have not actually done any testing with them yet. Instead I have been pondering how to proof the concept of pressure level sensing, and build accurate test circuits.
I built the mechanical portion, as shown in the picture. The 28 gallon (~100 L) kettle is included for a scale comparison. It consists of a plastic 1/2″ T, plenty of 1/2″ vinyl tubing, an old brass drain valve (long since replaced with stainless in on my kettles), and a wood support. This will let me test the pressure sensor with a very small amount of water, as opposed to filling up and draining 28 gallons at a time (not like that was ever even considered).
The circuit portion is going to require a little more time. First I need to find and purchase a 4 or 6 socket header that I can plug the sensor… I will run some wire back to a breadboard, and from there use my AD620 instrumentation amplifier IC to make it full-scale. I am thinking of taking it from the AD620 through a 12 bit SPI Analog to digital IC (MCP3202) and then to a 08M PICAXE chip. I haven’t worked out details, but I should have enough inputs and outputs on the 08M to bit-bang the SPI protocol and implement an interrupt / serial communication back to a master PICAXE chip when requested. If not, I’ve got a couple of the 14M chips that will definitely have enough power to do so - or I may even try playing around with the 28X1 and 40X1 parts that have native SPI support - haven’t really decided yet.
I also did some minor work on the VB.NET user interface - mostly getting the basic functionality for the “Designer” control to work. The biggest gap at this point dragging the pipe points around the screen, but I have a plan on how to do that. Cut/Copy/Paste is all working, the Zorder (bring forward/send back) is all working, as is shift-dragging and ctrl-dragging. Soon I’ll start work on the designer form (not just the control that displays and implements the changes). I don’t have any good / new screenshots to share, but I hope to complete a good quantity of work this week while on a business trip to Fayetteville. Once the workday is over and we’ve eaten dinner, I plan on locking myself in my room and working on the application rather than killing time, money, and brain cells in an overpriced and understocked pub. Seeing as Fayetteville is a military town, I do not have high hopes for the local craft brew scene.
Other things beer-related from this weekend:
- I racked 10 gallons of Witbier to secondaries, 5 gallons of which went onto about 5lb of cubed mangos (the “Mango Mama” witbier).
- I participated in the 2007 BUZZ-Off Competition and took 2nd place in the Belgian Dubbel category for Travellers & Tourists (TnT). My amarillo pale ale did well too (38.5), but did not place.
- I carelessly broke my favorite belgian glass (a Dogfish Head tulip glass, given to me by Sam Calagione at a book signing) and they are not made any more - DRAT!
The unfortunate demise of my tulip glass is most tragic. You were good to me - RIP.
