Thermocouple on BS2, possible just not recommended?

joneschj

Q1: I have a BS2.· I want to use the thermocouple with it, but the directions on the thermocouple pdf indicate that I should have a BS2p.· Will it not work with the BS2?· What are the limitations and why on the recommendation for BS2p?
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Quote from product description:
"The Parallax DS2760 Thermocouple Module capitalizes on this application and provides a complete connection between BS2p BASIC Stamp microcontroller and a standard thermocouple element."· Source, http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/CategoryID/49/List/0/Level/a/ProductID/96/Default.aspx?SortField=ProductName%2cProductName
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Q2: There is another product I was looking at, but I am unsure of this one as well because in this case it gives very little information.· http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/CategoryID/49/List/0/Level/a/ProductID/86/Default.aspx?SortField=ProductName%2cProductName
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Q3: Anyone have any recommendations on this next part I would appreciate it as well.· I want to periodically test the temperature of a tank of water.· These readings will be used to turn on a water heater which will warm the water to within a certain range.· Ideally I would be able to leave the probe or thermocouple in the tank, possibly even mounting it in the tank with some sort of switch to turn it off and on as needed.· The tank will have an agitator running 24/7 so I am not concerned with spot checking the tank, just a one time reading will be sufficient for my purposes.· Once I turn the heater on I am thinking of checking the temp of the water again every few minutes until I am within the range I need then turn off the heater.· The heater is a very lightweight system and will heat the water·very slowly, so I will not be in any hurry to monitor readings.
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Q4: Last question...· I have heard that leaving a metallic probe in water that has·a range·of acidity values over time·may cause the probe to leak electrons into my water causing an undetermined negative effect·.· I am specifically working with plants, so I do not want to kill them off or mutate them in any way.····

Thanks for any answers.
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Joneschj

Franklin

Q1 the DS2760 communicates with the one wire protocol and the bs2p stamp can talk that but the bs2 does not. You may be able to "bit bang" code to communicate though.

Q2 here is more info www.analog.com/en/temperature-sensing-and-thermal-management/digital-temperature-sensors/ad592/products/product.html

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- Stephen

Ugha

Q4:
I've never herad of this... I've worked with fish and fishtanks for years and I've seen all kinds of metallic things in the water.

One of the major concerns with adding items like pumps, filters, air pumps, thermal sensors, ect to a fish tank is the object altering the PH balance in the tank... not
the tank affecting the object.

I'm not a professional, but i'd say unless your applying a current to the water (breaking it up into its elements) then I'd see no harm in having the probe in the tank.

PS: Hydroponic experiments are cool and very rarely done... keep us updated on your project... [noparse]:)[/noparse]
...unless its the illegal kind :P

Tracy Allen

Q1) If you want to use thermocouples with the earlier BS2s that don't have the OW commands, another easy option is the MAX6674. It has a direct thermocouple to digital interface using SHIFTIN and SHIFTOUT. The earlier Stamps can't even bit-bank the OW protocol, which requires fast, accurate timing.

Q2) The Sensirion temperature/humidity sensor is great for measuring those parameters in air, but not underwater.

Q3) Other temperature sensors that might work for you would be the AD592 or the LM34, both sold by Parallax. They would require that you add an analog to digital converter to your BS2, and that you protect the sensor from direct contact with the water.

Q4) You can't go wrong with stainless steel. It is true that differing metals in water make little batteries with cathodes and anodes. Ceramic and glass are very inert, as are some plastcs.

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Tracy Allen
www.emesystems.com

John R.

Q4: It depends... Some plants or animals (fish, inverts, etc.) can be very succeptable to trace amounts of material coming from probes or other objects. Generally, if you do somewhat frequent water changes, this shouldn't be a problem. If the nature and material of the sensors (or other objects) results in a higher level of decay of the materials into the water, this might be more of a problem.

For plants, I'd be most concerned about copper.

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John R.
Click here to see my Nomad Build Log

plankton

If you have a length of heat-shrink tubing, some thin coax wire (or just two wire) then it is very easy to make a remote sensor using any of the Temperature Transducer that come in the TO-92 'can' package.

I've used all of these succesfully (just see Tracy Allen's website for details. <grin>)

- DS18B20 (Dallas 2-wire)
- AD592 (old school using RC)

Try to avoid using metals altogether since eventually they'll rust and in general metals are not good for fish, inverts, etc. For freshwater systems this is less of an issue, but for marine a very big no no. I have a fully mature reef tank with LPS, SPS, shrimp, fish, crabs, etc, etc and I have seen what happens when even trace amounts of copper get introduced... not good.

Remember wire is normally made of some amount of copper so take care in making sure none of it can be exposed to the water.

PS Hey Tracy, how about some circuits for interfacing with conductivity cells (for the purpose of measuring Salinity in ocean water - ~53 mS/cm - 53,000 uS/cm)·or pH probes? Please, Please, Please...

Scott

Post Edited (plankton) : 6/17/2009 6:38:47 AM GMT

sam_sam_sam

Here is a· temp sensor in a metal······ LM34CAH-ND··they cost a little more money than the plastic case ones do· Data Sheet

Encapsulates it in (fiberglass The kind used for boats resin) just make sure that it works·right before you Encapsulates the sensor

I have not tryed this yet but I think about a project where·I am going to do this very thing

·I·have a few ·LM34 in the metal can just wait for me to this·BUT just have not have
had the time to work on this project yet



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··Thanks for any··that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 6/22/2009 12:55:47 AM GMT