Cold spray, where do you buy?
in [Design]
|
Prev: Mosquito killer
Next: Finally!
From: Joerg on 11 Apr 2010 16:36 Frank Buss wrote: > Joerg wrote: > >> Yup, I have used substrate diode for stuff like this but those solutions >> are often met with outbursts of disgust at design reviews ;-) > > If you have the space on the board, I would use the SE95, because no > calibration is needed. ... Problem is, that series is no-stock too often and that's somewhat of a red flag for me. I2C stuff sometimes goes lalaland after a while. Mostly I prefer a simple analog method and then either into an ADC, or dual-slope when it has to be cheap. > ... I've used it with high sampling rate and digital > lowpass filter for a resolution of 0.01�C. It's fairly stable and > intersting to see the temperature falling, when slightly blowing it. I > think this could be used for something like this: > > http://www.coolest-gadgets.com/20060530/electric-candles-that-you-can-blow-out/ > > :-) > Oh man, electric candles with matches. That reminds me of the 2nd generation walkman that my classmates had in school. Those had a "talk-through" button which allowed a conversation with other kids. Conversation, what a concept :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Frank Buss on 11 Apr 2010 16:57 Joerg wrote: > Problem is, that series is no-stock too often and that's somewhat of a > red flag for me. I2C stuff sometimes goes lalaland after a while. Mostly > I prefer a simple analog method and then either into an ADC, or > dual-slope when it has to be cheap. I know a product, which uses it for 6 years and I think the sensor is a standard chip, which will be in production for some more years. But the MAX6633 looks very similar, could be replaced with no hardware changes. How do you avoid (or implement) calibration for analog and ADC? You are right, if you just need the information "it is hot" or "it is cold", then you don't need complicated chips. -- Frank Buss, fb(a)frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
From: John Larkin on 12 Apr 2010 15:34
On Sun, 11 Apr 2010 21:48:12 +0200, Frank Buss <fb(a)frank-buss.de> wrote: >langwadt(a)fonz.dk wrote: > >> I seem to remember that some (xilinx?) guy has a patent on using >> the ldvs input as a comparator for an ADC > >A simple digital input would do it, too. E.g. with two pins of a >microcontroller you can use a standard LED for light emitting and light >sensing: > >http://www.merl.com/reports/docs/TR2003-35.pdf > >Maybe this could be used with a FPGA, too, for temperature measuring with a >1N4148. But I don't know, if it needs a schmitt trigger input, which is not >available for all FPGAs (e.g. only some configuration pins on Cyclone II, >but Xilinx FPGAs have schmitt trigger inputs with 100 mV to 200 mV >hyteresis). > >Of course, on page 34 of this journal: > >http://www.xilinx.com/publications/archives/xcell/Xcell19.pdf > >there is a simple schematic with only two resistors and two FPGA pins for a >user defined schmitt trigger :-) That can get tricky, as can adding external hysteresis to any comparator. If you get a spike that's faster than the internal loop-back delay of the device, the positive feedback arrives too late to do much good. So a rising edge with noise, but less noise than the theoretical hysteresis, can still double-clock things. Better is to use two LVDS inputs as comparators. Apply the signal to both, and set up the other sides with the desired thresholds. Drive an RS flipflop internally. John |