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watson.fawkes
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Most all of these inexpensive gas
sensors use catalytic oxidation and temperature differential as their physical basis. What the catalyst preferentially oxidizes in ordinary atmosphere
determines what the sensor will pick up. If you used a selective catalyst, you get a specific result with less chance of false positives. I don't know
much about the catalysts, except that (1) they are often compounds or mixtures I don't see used in other contexts, and (2) they're deposited in thin
layers in very small amounts so that expensive catalyst precursors still make inexpensive chips.
The TP-4 sensor part in that PDF looks like it may use a broad spectrum catalyst. The only specific things I saw were hydrogen and alcohol (presumably
ethanol) and hints that it may pick up nitrogen oxides and ammonia.
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IrC
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Maybe it's just me but it is a little depressing there is not much interest in the Arduino at SMO. Hopefully this project will spark some. You will
need to get Eagle to study the circuitry and you can download a 22mb zip at github of His project from a link on the page.
Ardustat "The Ardustat is my (in progress) open source successor to Jonny Galvo. It uses a standard USB-Arduino unit with a custom designed
daughterboard to provide:
A galvanostat with a current range from .1 microA to 10 mA
A potentiostat with a potential range from 0 to 5V with 5 mV resolution.
The Ardustat is a two electrode system for the time being, primarily for characterizing capacity and power delivery of small batteries,
supercapacitors, and DC energy harvesting devices such as photovoltaics and thermoelectrics."
http://steingart.ccny.cuny.edu/ardustat
"Science is the belief in the ignorance of the experts" Richard Feynman
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arsphenamine
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Quote: Originally posted by IrC  | | Maybe it's just me but it is a little depressing there is not much interest in the Arduino at SMO. |
SMO cut
a deal with Arduino.cc.
They don't host chemistry forums and SMO doesn't host Arduino forums.
Adafruit, google, makezine, github, et.al., operate under similar constraints.
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IrC
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While I am guessing this is meant to be ironic I can see a flaw in the logic. The Arduino is a goldmine for chemistry with the incredible number of
shields already on ebay for very low prices. Monitoring PH, temperature, ion concentration, current flow in an electrolysis cell and on and on.
Combined with SD card shields for data logging, Xbee for talking to computers in other areas, etc., controlling things like current and voltage as in
a plating or chlorate cell where voltage is reduced when temperature rises and so forth. All while a log file is being written to a 2 GB SD card. The
list is so endless I would not know where to begin in describing the possibilities.
Edit to add a few examples:
http://www.robotshop.com/bnc-ph-sensor-shield-arduino-3.html
http://practicalmaker.com/category/store/arduino-shields
http://www.reefsanctuary.com/forums/diy/73570-arduino-ph-orp...
A post about PH measurements combined with other parameters and His site below.
http://saltydogaquariums.webs.com/apps/blog/entries/show/790...
Does not take much thought to consider his aquarium dosing system could add various amounts of different chemicals to an ongoing reaction while other
parameters are being monitored, you could even add programmed stop and/or alert functions.
As I said the list is unending.
http://practicalmaker.com/category/tags/macroduino-code
You can even find schematics and code if you look at His macroduino code pages.
[Edited on 10-10-2012 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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arsphenamine
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| Quote: Originally posted by IrC | | While I am guessing this is meant to be ironic I can see a flaw in the logic. The Arduino is a goldmine for chemistry with the incredible number of
shields already on ebay for very low prices. |
Intrinsic merit is necessary but insufficient.
It's about numbers, numbers of people, critical mass of involvement.
Perhaps the number of people interested in chemistry is not only numerically smaller but proportionally smaller than those interested in more general
programming+maker projects. There is limited overlap of the populations.
If there is a particular Arduino-based project that you could put to work, then do it. Take pictures as you go. Post them.
I'm no Kevin Costner fan, but if you build it, they will come.
For the record, I _am_ an Arduino fan.
[Edited on 10-10-2012 by arsphenamine]
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watson.fawkes
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| Quote: Originally posted by IrC | | The Arduino is a goldmine for chemistry with the incredible number of shields already on ebay for very low prices. Monitoring PH, temperature, ion
concentration, current flow in an electrolysis cell and on and on. |
The larger issue is that there's been
fairly little interest on this forum for instrumentation and calibration. Occasionally there the over-ambitious fellow who wants to talk about
something that never comes to fruition, e.g. notably NMR. There's a small cadre that are trying to get surplus instruments running, but they aren't
hacking the insides of them.
Take pH, for example. Actually building a pH meter is rather more multidisciplinary than it might appear at first glance. pH electrodes are a classic
low-current source. Ideally, you want to measure them at zero current, and that's hard. This is required for decent accuracy, and if you don't need
that, well, there's no particular reason not to use COTS equipment. Zero current measurement requires you to eliminate or mitigate all source of stray
capacitance, since that capacitance must be charged (requiring current) in order to equilibrate the voltage at the sense amplifier. Elimination means
knowing something about the physics of capacitance. Mitigation means building a guarded electrode, which requires a guard amplifier, guard rings on
the PCB (if you're doing a bang-up job), and shields within the probe cable. Proper sensing of thermocouples has similar issues (though not as
severe). Related to this is the reason that precision RTD's use three wires (and high-precision use four), because you can't drive too much current
through them lest self-heating cause inaccuracy. These details matter less in specific than the fact that the overlap of chemists and
people-who-know-instrumentation-electronics is really quite small.
And much less instrumentation, the dominant trend here is not in building apparatus in general. A few people have experimenting with this. At this
writing, for example, Magpie's phosphorus experiments are active, and they're as much about equipment as reactions. This kind of experiment, however,
is not the norm here, where most people do their work in standard glassware.
I'm not bewailing this situation, particularly. I am personally quite interested in instrumentation, but I haven't had the attention to pursue it
lately. Personally, I think there's a good piece of low-hanging fruit in an open-source melting-point apparatus. The key to making this useful is that
webcams have gotten dirt cheap and image manipulation software on personal computers is easy to use. Point a camera at the sample, watch for the phase
change, and shut off automatically. Almost as easy to do with the basic setup is DSC (differential scanning calorimetry) which gives you heat capacity
etc. of the sample in addition.
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IrC
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Good points all. I wonder though if hyper accuracy is so mandatory for the do it yourself chemistry experimenter running a reaction that is not so
critical. The inexpensive setups I have looked at do a decent job controlling the PH of aquariums for example. Mainly I was just trying to stir up
some interest in the subject. I have only recently acquired several Arduinos and a few dozen different shields to experiment with. I am trying to
teach myself enough coding to create my own useful devices which right now relate to metal detector discrimination and Geiger counters. Some of the
language seems common sense as I have worked with basic for many years, and some I am having difficulty with. Right now I am playing with code to
pulse a MosFet to drive the high voltage thereby eliminating some circuitry.
I started wondering about using the ADC in voltage regulation schemes. This lead me to wonder about monitoring the GM tube for operating
characteristics where the circuit would adjust to whatever type tube it saw. Going further I started being curious about closely monitoring where on
the curves the tube ran as a way to determine the actual energy. This would make it easy to differentiate units from counts per minute over various
sources with differing decay rates and energies. Still far above me in coding but I can see the concept and that it can work. As I went along I
started thinking about so many other ways it could be useful in chemistry. For example the member wanting a thermostat controller with LCD readout.
"Science is the belief in the ignorance of the experts" Richard Feynman
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arsphenamine
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| Quote: Originally posted by watson.fawkes | | Related to this is the reason that precision RTD's use three wires (and high-precision use four), because you can't drive too much current through
them lest self-heating cause inaccuracy. |
It is common practice to separate sensing leads from drive leads.
The topic is frequently covered in analog power suppy regulation design texts.
Platinum devices typically receive a tiny excitation current to minimize self-heating.
For Pt100 RTD's, this usually translates to 20 mV, 200 μA, levels which, using 6 foot long leads,
are usually down in the noise floor of lesser devices and which make a separate sense lead mandatory for useful measurement.
| Quote: | | These details matter less in specific than the fact that the overlap of chemists and people-who-know-instrumentation-electronics is really quite
small. |
Worse, there are many chemists with a negative interest in crufting up their own
apparatus, to judge from my discussion of the book Building Scientific Apparatus with one of the university analytical chem prof types.
_Physical_ chemist types are a different story.
On the practical side, if you have a hobbyist level of electronics proficiency
(read schematics, do Ohm's Law calcs, solder without destroying things),
you can read a few dozen application notes and get usefully familiar with
issues in small signal measurement.
Analog Devices, National Semiconductor, and TI have a plethora of app notes with worked calculations.
There is a good deal of hobbyist-level pedagogy published in the late 80's.
Search initially on the words "instrumentation electronics design" and refine as desired.
*sigh* I used to do a lot of that stuff and had forgot until you reminded me.
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watson.fawkes
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| Quote: Originally posted by IrC | | I wonder though if hyper accuracy is so mandatory for the do it yourself chemistry experimenter running a reaction that is not so critical.
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In my own experience, the difference in skill between someone that can design a decent measurement circuit
and one that can design an accurate measurement is just not that large, that is, not large compared to the not-insignificant body of knowledge needed
to design any circuit at all. And I mean analog circuits; digital doesn't count here.
One simple exercise is to drive a high-current LED from a low-power CMOS signal using a single NPN transistor. Run the transistor in common-emitter
configuration at saturation. In addition to the digital output, you need a base resistor, a collector resistor, a transistor, and an LED. It's a good
exercise because you really need to understand what's happening in the transistor, then compute the currents, voltage drops, and finally resistor
values. Anybody who can do this can learn to understand instrumentation electronics by applying effort.
The hard part comes when you have to start doing design with noise budget. That's the difference between ordinary accuracy and high accuracy.
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arsphenamine
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Arduino Due, 32-bit
Massimo Banzi leapfrogged the 16-bit Atmel cpu's, has finally released the
Arduino Due based on the 32-bit ARM SAM3X.
The Due is compatible with existing 3.3 Volt shields.
http://www.adafruit.com/blog/2012/10/04/due-arm-powered-ardu...
Much IO, more bits, more memory, fast enough to do audio DSP in real time.
NOW how much would you pay?
$49
Not a Bean: When following "Arduino", Due is pronounced DOO-eh,
even if you aren't Italian.
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IrC
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Smaerd, I found this version of a temperature controller which seems very easy to build, complete with schematic and ready to use software. Maybe you
can use it.
http://www.myplace.nu/avr/thermo/index.htm
"Science is the belief in the ignorance of the experts" Richard Feynman
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smaerd
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Thanks for looking out IrC. My next pay-check is going to parts for the DIY roto-vap I've had haulted for about a year now, and then tax-returns and
such will probably go to a PID controller+thermocouple. That's a really nice set-up though it's definitely something to keep in mind I'll do some
research on cost and see what's most appropriate(sadly $ is one of the biggest factors in my projects). One of my upcoming projects requires stable
temperature control so this does need to get done.
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IrC
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I liked the use of LED digits because unlike LCD you can see the reading from further away and at greater angles, even in a room with poor lighting.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Oscilllator
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The only thing stopping me from buying many many arduino boards is that I cant think what I would actually do with them once I got them
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arsphenamine
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In order of increasing importance, you only need one Arduino, one sensor, and an itch to scratch.
My first was a cheap gaussmeter.
Arduino+display+sensor was $51.50
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Solomon
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I have an Arduino mega 2560. I have designed several programs. One was a simple code that ran an RGB led in a fade mode while simultaneously operating
a speaker that you could adjust the sound wave it produced via a potentiometer. You can also use Arduino to make your own satellite.
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plante1999
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Best arduino/chip
I want to automatize some things in my lab, temperature monitoring etc. I would like to know what is the best "kit" to do so, most functionality
etc... I'm not really good in theses things, so if anyone can help it would be appreciated.
Thanks.
I never asked for this.
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Funkerman23
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http://www.sciencemadness.org/talk/viewthread.php?tid=23062
http://www.sciencemadness.org/talk/viewthread.php?tid=16440
while I can't help you just yet the two threads above might help. There was another excellent thread on this but my crappy sleep seems to have removed
its name from my memory. If I find it I'll post here.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: fixed
internal link(s)]
[Edited on 30.7.13 by bfesser]
" the Modern Chemist is inundated with literature"-Unknown
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IrC
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Most usually pick the UNO R3 such as:
http://www.ebay.com/itm/Arduino-Starter-Kit-w-Uno-R3-Ultraso...
However in my mind the Mega2560 is a better choice because you do not so quickly run out of I/O:
http://www.ebay.com/itm/arduino-mega-2560-r3-starter-kit-mot...
You can also just buy the Arduino and carefully pick the other devices based upon your goals, say pick the shield most useful to go with your 2560.
This would save you money compared to a kit price which likely includes items you do not need. However if starting out and learning to code is your
goal I for one would pick the kit. In fact even though more costly the 'non clone' choice for about $130 is best as that 170 page book included is
worth it's weight in gold.
http://www.ebay.com/itm/The-Arduino-Starter-Kit-Official-Kit...
Just keep in mind it comes with a UNO R3. Only about $18 to add a Mega2560 clone later on when you find you need more lines for I/O.
http://www.ebay.com/itm/ATmega2560-16AU-ATMEGA16U2-Board-Fre...
Probably the best route, total investment around $150. Later you can dedicate the UNO to some lab controller and still have the kit with the 2560 for
learning/playing. Bear in mind sketches designed for the UNO in the book/kit may need alterations to work with the Mega.
Myself being cheap I just bought the clone and spent time studying at http://www.arduino.cc/. However I strongly suspect if I had bought the official kit I would have learned at a much faster rate.
[Edited on 7-30-2013 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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smaerd
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I can't say what is best or what is worst or anything like that. I can say I'm very happy with my arduino leonardo.
My advice is this, research before you buy anything. See what's been done before, what the limitations are of arduinos, stuff like that. Then buy the
board, several little bread boards, jumper wires, and lots of little pieces for your projects. Good idea to have an assortment of capacitors, and
resistors. The rest depends on what you plan on doing really.
Also don't forget this - http://ruggedcircuits.com/html/ancp01.html
This quick article saved me 25$!
[Edited on 30-7-2013 by smaerd]
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bfesser
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<strong>plante1999</strong>, Adafruit has a nice <strong><a href="http://www.adafruit.com/products/68" target="_blank">Starter
Pack for Arduino (Includes Arduino Uno R3)</a></strong> <img src="../scipics/_ext.png" />.
You could also check out the small <a href="https://www.tindie.com/products/category/platform/arduino/" target="_blank">Arduino clones and
accessories on Tindie</a> <img src="../scipics/_ext.png" /> (although, the new site doesn't load properly for me).
And, of course, SparkFun has a large <a href="https://www.sparkfun.com/categories/103" target="_blank">selection of shields</a> <img
src="../scipics/_ext.png" />.
I have an <a href="http://arduino.cc/en/Main/ArduinoBoardUno" target="_blank">Arduino Uno</a> <img src="../scipics/_ext.png" /> R3
that I'm very happy with. But, if you'd like to go a little more advanced, I suggest a <a href="http://www.adafruit.com/products/1014"
target="_blank">Raspberry Pi</a> <img src="../scipics/_ext.png" />—which can be interfaced to an Arduino for added I/O (among
other benefits). I've been wanting to try the <a href="http://wyolum.com/projects/alamode/" target="_blank">AlaMode</a> <img
src="../scipics/_ext.png" />, but don't have the funds yet.
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bfesser
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Threads Merged
30-7-2013 at 13:33 |
Texium
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Thread Moved
20-12-2023 at 12:50 |
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