On Thursday, 10 March 2022 08:36:39 EST andy pugh wrote: > On Thu, 10 Mar 2022 at 13:00, gene heskett <[email protected]> wrote: > > But neither of the $23 sensors I bought, actually works. black to -, > > red to 5v, green to dvm on my test table, one rests at nominally 1 > > millivolt, the other at around 27 millivolts which doesn't change > > with the applied pressure. > > What are the sensors? Are they possibly PWM output and need a pull-up? > The type of sensor isn't stated.It just says the output on the green wire is .5 tp 4.5 volts with a 5 volt supply. Not terribly informative. Claims a .5% total non-linearity once the math has been done. Nowhere is a pullup mentioned. Ohmage at zero pressure, of any lead to any lead is high, 4.7 megohms on my dvm's, from the green wire, and around 15 megs from black to red, infinite if meter probes reversed. So there would appear to be polarity protected circuitry in them. And I'll admit I didn't think to try a pullup. Can I plead oldtimers?
The next candidate I've found is a digital barometer with a hose nipple input, that claims similar accuracy after the offsets are mathed out, up to 40k but doesn't state the unit! That I'd have to assume would need some sort of translation to get its 16 bit seriel output to an SS mesa interface. Sells for $12 for three of them, but delivery dates were in early may so I canceled that. From the looks of the board that may have been easy as one of the terminal pads is labeled "osc". It may be easy if mesa exported an SS clock. But I don't recall seeing that in the mesa docs. SS is balanced but apparently self clocked. Seems like this should be a simple problem, but the pedlars are keeping secrets about how to use this stuff. I thought somebody here would have already solved this with a $3 part and some clever hal magic. I can cobble up a manual control easy enough just by cloning my misters wetness control. There, I'm banging that peristaltic pump with both the on time and the dead time adjustable from some python pins, time actualy shown in gui sliders, so the mister can run till the shop compressor burns up, on one 8oz coke bottle of diluted koolmist. But I thought it would be "cool" to regulate the pressure with a pwmgen signal to one of those $6.50 BTS-7960 full bridges that can handle 25 volts at 43 amps with zero heating. These teeny compressors are power mizers, well under an amp each at LRA & 12 volts, only heating for a 30 minute run is the plastic top of the diaphram head and thats quite minor. And they'll beat the daylights out of burning up the shop compressor just to feed this piddly stuff. And 50+db quieter to boot. Thanks Andy. > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
