As an aside to my testing of the amplified pressure sensor of the prior posts, I wanted to spend some time evaluating an alternative approach which would appear to not require amplification.
Initially, when I began researching flexible pressure sensors, I came across some exceedingly interesting projects made available at Instructables by a user named Plusea.
After looking over some of the sensor related project details and watching a few of Plusea's YouTube videos, I was convinced that my project was possible.
I immediately contacted Hannah ( ... Plusea) and ordered a fabric sensor kit from her Etsy shop with high hopes that operational range of this unique dynamic resistor would fit for my application.
Given that Hannah was going to be shipping my order out from Germany, and that I was pretty impatient and wanting to get up an running on this application, I did a little more Googling for other possible approaches and found a commercial manufacturer of flexible pressure sensors right here in the Boston area.
Both sensors appeared to work similarly in that they both were effectively acting as dynamic resistors, preventing current flow with no pressure (i.e. like a switch switched to off) and then slowly allowing more and more current (i.e. less resistance) with greater and greater application of pressure.
Of course, the package of sensors I ordered from the Boston supplier came almost overnight and thus I got up and running with them first.
Right from the start, there was more to using this sensor than the simple Velostat fabric swatch of Plusea's construction.
Most notably, it was suggested by the manufacturer that the sensor be paired with an either a single or dual supply OpAmp (... as we now well know from prior posts) which took me down the path of assuming some level of circuitry allocated just for proper function of the pressure sensor.
Mind you, my intent was to minimize this circuitry (low voltage OpAmp, probably single supply, minimal supply voltage) but I was firmly on the path of detailing amplifier circuitry and vetting power scenarios just for the pressure sensor (... remember there are other sensors as well in my project!).
Well, last night I finally got around to putting together Plusea's fabric pressure sensor and sure enough it works great!
It produced what preliminarily appears to be vary consistent readings even at very heavy loads... I even put my whole body-weight on it ( ... about 178 lbs)... and all with only the little current put out by my digital multimeter.
One thing though, the change in resistance appears very non-linear in that there is a large change in resistance with very light weight and then progressively less and less change as you pile on more weight, but the sensor appeared to be generating some very consistent readings in any event.
So, this appears to frame a bit of a smack down of sorts... which sensor is the best option for this application given all the constraints and requirements?
Obviously, I now need to create a comparison matrix.
Best to all...
No comments:
Post a Comment