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  1. #1
    I am in the process of developing my own user interface program to monitor my HVAC equipment.

    I would like to have a USB interface between the sensor circuit board and my PC.

    Anyone have any suggestions for a mfgr for a HVAC monitoring (only) circuit board and matching sensors?

    To get an idea of what I am working on goto here:

    Thanks in advance...

  2. #2
    Join Date
    Mar 2004
    I looked at your web page...

    First, the graphics are nice and the information shown is good, but if you are trying to break ground and present a revolutionary new way of monitoring HVAC equipment you are many years behind. Virtually every DDC controls package available has graphical interface of some sort. If this is just for your personal use at home, kudos!! Carry on and have fun.

    Second, you might think about switching the inputs to your calculations which show your TD's for outside ambient vs return ambient and your return ambient vs supply ambient...they are usually represented as positive numbers.

    Finally, to answer the question in the my knowledge most boards communicate with the front end with either RS232 or CatV, and on older boards ARCnet cable, I have not seen one which uses USB. I suspect your goal is to be able to set your laptop next to the board, plug in, and go to work. RS232 and network cable for direct connect to a DDC controls board is fast, I don't think there would be an advantage using USB, but I'm an HVAC tech not a computer tech.

    Good luck with the project!!!
    Def. of insanity: doing the same thing over and over again expecting different results!!

  3. #3
    ts ac tech,

    Thanks for your response.

    I am not a hvac tech, and I wanted something simple to indicate GOOD or BAD, and if BAD call a hvac tech to fix it. I looked at some of the state of the art stuff you mentioned.... they are very impressive, however way to much info/data for a non-tech homer owner like me.

    If USB is not an option, what CAT V(TCP or UDP) mfgr's do you recommend that would have 8 sensor input monitoring boards (no control) that have a CAT V ethernet interface to the PC.

    I not looking for lightning fast, just something that would be accurate and durable, stay calibrated for a reasonable timeframe. I would appreciate any suggestions or recommendations.

    [Edited by aguada on 08-04-2005 at 09:30 AM]

  4. #4
    Join Date
    Feb 2005
    there are many USB I/O manufacturers, like:

    If I were you though I would look into "1 wire" devices.
    Slow, but networkable and cheap. have been used in weather stations (which are mainly input points)for years, many starter kits out there and nice little graphics interface packages too.

  5. #5

    Regarding..."many starter kits out there and nice little graphics interface packages too."

    Any URL's you can provide would be most helpful...I am not having any luck on the web searches (excite, google, etc).

    "1 wire" devices... are you refering to 1 wire Sensors... if so... a couple of url's would help me alot.

    Thanks in advance...

  6. #6
    Join Date
    Feb 2005

  7. #7
    Amigo...Thank you sir!

    I came across this little puppy while referencing the URLs you provided.

    What are your thoughts?

  8. #8
    Join Date
    Feb 2005
    looks good.

    I think for your application rule of thumb for system components should be "simple" . Hardware and software.

  9. #9
    To All,

    Thanks for all your help... I found what I was looking in Air Temp and Airflow sensors at EBTRON. You guys have been most helpful... BTW thanks to the HVAC forum grand poo-pahs for providing this service.

    Catch ya'all later on the flip side... when I get this puppy working.

    AG OUT

    [Edited by aguada on 08-04-2005 at 07:51 PM]

  10. #10
    Join Date
    Jun 2005
    Wheeling, Il.
    Nice work on the output side. Your problem is on the input side. I agree with the theory of using the system to give an indication of a problem. The root problem is sensor cost. Wireless is the way to go. I believe you need 8 points. OAT, DAT, RAT, RATwb, Suction line T, Liquid line T, Liquid line P and Suction line P. Using these 8 points and information on the system such refrigerant type & heat output, you get the status of most light commercial & residential systems. Good quality sensors & software will cost over $2,500.00. I have looked into developing a portable system to prove a split system or rooftop is charged and running correct. There are a few out now. By the time I add up hardware, software and throw in a laptop or pocket pc it gets pricy. The price of 8 channel a to d boards and DAS systems have come down.

  11. #11

    1st allow me to say that I have greatest respect for HVAC techs such as yourself. From a non-hvac tech home owner point of view I am not the least bit interested in measuring or acquiring detailed hvac data ie the number atom molecules contained one cubic centimeter of ambient air during the latent heat transfer process...(LOL) so-to-speak... that level of detail is what you guys do... and do it well I might add.

    I thank you for taking the time to analyze what I am after...

    drrtu you nailed it.. "I agree with the theory of using the system to give an indication of a problem."

    Let me take that a step further from an average home owner point of view... what I am trying to develop is, something that indicates that the Heat/Cooling system is performing within the design limits specified by the mfgr for size of the home, ducting, location, elevation, etc. I refer to it as the "IT IS WHAT IT IS" system performance factor for the average home owner.

    The indications (GOOD vs NEEDS SERVICE), is all I need to know (and all I want to know). If and when I get a NEEDS SERVICE indication, I call my HVAC (Stevensons Air Care) tech, and give him the data as to what the NEEDS SERVICE indication is related to, so when he shows up at my front door, he already has some idea what he is walking into, and in theory hopefully shave off some on-site troubleshooting time to fix the problem, which in-turn saves me some money.

    Another angle is the "IT AIN'T BROKE" factor for the average home owner. For example... its 100 degrees ambient outside and I have my temp set at 65 degrees, and the best the system can do is maintain 78 degrees(for example), which by design is absolutely within spec for the system, and therefore, there is nothing wrong with the system "IT IS WHAT IT IS" (sorry the previous statement was poorly written, but I hope you get my point).

    Regarding "Good quality sensors and software will cost over $2,500". I totally agree with the good quality sensors part and the Wireless... wireless is way out of my league at the present. I have been lead to believe that Analog sensors are the most durable and stay calibrated longer than the Digital Sensors. I realize that the Analog sensors are slower, but for my use and intent they appear to be adequate... speed is not necessarily a requirement for me right now... my best guess is that a complete poll of all sensors/data can be completed and displayed easily once every 2sec or less, which is more than adequate for my needs.

    Currently I am considering the (8 channel input) E-TEMP as my DAQ interface device to connect the sensors to, and upload the sensor data to my PC via Ethernet TCP.
    --The E-TEMP device has a Built-in ambient temperature sensor capability that covers my (OAT) requirement.
    --Two more additional Temp sensors to cover my Liquid and Suction line Temps.
    --No power supply required, CATV data transmissions are good for approx 130 ft without dropping any 1's or 0's... in my case I only need about 50ft of CATV, from my HVAC equip to my PC.
    --The Softwire software is free with the E-TEMP device, and I can tailor my front-end GUI to interface with the Softwire or write my own LAN interface if need be.

    --Then attach two of the EBTRON (Dual AirTemp/Airflow) sensors.
    Two each will cover both my Return/Supply Air Temp and FPM requirements.

    I estimate the HVAC DAQ monitoring hardware for my intended design will run me less than $700 retail.

    Regarding the additional inputs you mentioned:
    RATwb (wb=wet bulb I assume)... what will that do for me data wise, and how do you see that data being used and interupted. I am not questioning your suggestion...remember I am not a HVAC tech, so I have to ask..sir

    Liquid/SuctionP (P=pressure I assume). I mentioned that to my HVAC guy... and he said don't go there, he told me it is against the law to put in a pressure sensor in the AC lines. Is there a analog sensor available that can measure internal liquid/suction line pressure...EXTERNALLY? If so, pls provide me some links to some web pages.

    DAT? I think AT = Air Temp... D= Dry?

    [Edited by aguada on 08-06-2005 at 06:43 PM]

  12. #12
    Join Date
    Jun 2005
    Wheeling, Il.
    I think we are both working on a similar product but are on different paths. There are a lot of companies selling data acquisition hardware. Your idea seems more like the “check engine” light on your car. Mine would help a field tech diagnose the problem and could be run at a later date.

    I believe you do not have to measure airflow for the following: 1. sensor accuracy – in order to obtain good readings you will have to install a flow grid or conduct a traverse. 2. Output from other sensors will have you looking for an airflow problem. IE low flow can show up as increased delta t or low suction pressure. 3. Cost and calibration. The units I have used in the past have been 4 to 20ma outputs.

    You need to check to check both pressures. Subcooling and superheat are two calculated values that are very important. The down side is pressure is a costly to purchase and install.

    Return air wet bulb is needed as an input to find out the entering air on the evaporator. Most equipment manufactures can provide charging charts. Most use RATwb. Most wb sensors are also 4 to 20ma. Don’t forget you can always read RH or dewpoint and convert with software. 4 to 20 loops require a power supply.

    This vendor has a good line for one stop shopping

    If you are looking for a very cheap solution, try just using temp. sensors with the system working. IE at known OA and indoor points the system should give similar DAT points. If the output varies from past data you get the alarm. Throw in a delta p switch across the filter and you have a custom data profile of your system.

  13. #13

    Thanks for your response...

    Yepper..You are EXACTLY correct...."Your idea seems more like the “check engine” light on your car."

    Msg received..."If you are looking for a very cheap solution, try just using temp. sensors with the system working. IE at known OA and indoor points the system should give similar DAT points. If the output varies from past data you get the alarm. Throw in a delta p switch across the filter and you have a custom data profile of your system."

    Is the Delta-P switch go by another device name...I am having problems finding one specifically designed for Airfilter use/measurement.

    Thanks in advance...

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