UAT-1 1

[MoonshadowXIII]

thread240-24000
"DRWeig (Electrical)
28 May 02 10:30
Hi BFuddled,

Kele has a device (UCS-121 or UCS-221) that does this trick, and if you need to scale the input, there is a UAT-1 that can do that too.

Have a look, the web is

http://www.kele.com,

and it's in the product catalog under output transducers.

Let me know if you need more info.

Old Dave"

Dave,
I know this was thread was a while back, but I have a question for you. BFuddled wanted to turn ON at a set voltage then OFF again at another voltage. I too want the same thing. I want to come ON at between 3.5vdc and 5vdc, anything above or below I want to be OFF. Question: Will the UAT-1 you mentioned accomplish this? I have read the docs from KELE, but I'm afraid I just don't understand the lingo enough to know if it will. If it isn't too much trouble for you, could you please let me know if it will do what I described?
Thanks!
Moon

 

[DRWeig]

Hi MoonshadwXIII,

Full disclosure: I am a consultant to Kele. Other companies have similar products, you may search for 2-stage sequencers to find them. I worked many years with the fellow who designed these products, though, so I am comfortable saying they're reliable.

The UAT-1 you grabbed fom the old post is for re-scaling or converting analog signals if needed. Example: if you have a vibration transmitter with a 0-1 VDC output and you'd like to hook it to a controller that expects a 0-15 VDC input, a UAT can be set up to make the conversion and allow the controller to access the full span of its input.

For the case you described, an on/off signal based on voltage, the UCS-221E will work. To get an interval of 3.5 VDC to 5.0 VDC, run your controlled load in series through the NO contacts on the low relay and the NC contacts on the high relay, and adjust the setpoints to get the action you desire. The total output will only be closed when the input is between the two settings.

Limitations: You didn't state what sort of load you're controlling, nor the accuracy you desire, nor the acceptable deadband around the switching points. Check the specs carefully against your needs (data sheet attached) to make sure it will work in your application. The Kele model has setpoint deadbands that can be minimized, but they're still significant. With the factory-included differential resistor, you can set it to turn at 3.5 VDC and off at 5.0 VDC on a rising input voltage, but it will turn on again at 4.625 VDC and off at 3.125 VDC on a falling input voltage. This 0.375 VDC differential can be changed to 0.188 VDC by substituting a different differential resistor, but I'm not sure how low it can go. The differential is required to prevent short-cycling of the output. Kele tech support can give you more info.

If you need a tighter device, I believe Omega Engineering has some precision models, and others who make precision temperature controls may have similar.

Hope this helps!

Good on ya,

Goober Dave

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[MoonshadowXIII]

Dave,
Thanks for the fast reply. Sorry if i seem a little dense. If it takes a hammer to get the job done, I'm your man! If it takes electronic finesse... uh well that's why I'm here

Let me explain what my goal is and them maybe you can advise a better solution. I have a small greenhouse I grow Orchids year round. It's just a hobby I enjoy. I built it out of old windows I salvaged from the local glass shop. It's about 200sq ft total. I have automated the environment, temp, humidity, watering etc...
I experimented with CO2 enrichment last year and got notable results. I invested in a CO2 monitor (see

http://www.ge-mcs.com/en/co2/wall-mount/ventostat-8000-series.html

) so I could maintain optimal PPM in the greenhouse. But I have to turn on and off the tank manually. I tried a timer method, but the results are unpredictable. Now I want to automate the CO2 bottle (see

http://www.amazon.com/C-A-P-Co2-Regulator-Valve/dp/B000QGU4XQ

). The monitor puts out 3.5vdc at the minimum PPM, and 5vdc at the max PPM. I already have a relay to trigger the CO2 bottle (see

http://www.aliexpress.com/store/pro...A-10A-3-32VDC-24-380VAC/708669_496590692.html

). What I need is a device that will trigger the relay when the input from the monitor is below 3.5vdc and shut it down if the input is 5vdc or higher.
I have found commercial devices to perform this, however they are very expensive. I was hoping I could just hook up the monitor to the relay and be done... but not that simple it seems (as I said I'm a little dense with electronics). I need something in between the monitor and the relay, or a specialized relay, to automate the CO2 regulator valve.

I hope that all made sense and you have all the data you need. My budget for this $50. I can solder fairly well and am willing to build my own, but I would require a kit or something step-by-step in order to overcome my dense nature in these matters

Thanks!
Moon

 

[IRstuff]

These things can be tricky. For example, a direct connection would certainly open and close the valve, but because of the lag in the CO2 concentration being even distributed, you'd potentially wind up consistently either over or under your desired setpoint by a fair bit.

This is the sort of thing that a PID controller does. Depending on much much DIY you can tolerate, you can either buy an off the shelf controller, with its commensurate cost, or you can buy something like an Arduino board and implement your own PID loop in the processor. see:

http://www.sparkfun.com/products/10914

for a typical Arduino board. Obviously, with that, you'd have to jigger something to get the monitor outputs into the board and the relay controls out of the board.

TTFN
faq731-376

 

[MoonshadowXIII]

IRstuff - I took a look at the link you provided.... have you ever been driving on a mountain road at night, came across a deer in the road? You know that look the deer gives you? If you could only see my face now

A quick Google search for "PID controller" yielded many, although most all seemed temperature or motor related. Will spend some more time researching this subject.

Your point about over/under PPM due to lag: I considered this, however it seems to me that the small sq ft of the greenhouse combined with fast response of the GE monitor and if I set the trigger point for max just a bit low, I shouldn't really have too much trouble there. My biggest worry would be more that the humidity is controlled by an exhaust fan and automatic window, thus renewing the air in the greenhouse and taking all the CO2 out with the humid air. My flowers like high humidity (60-80%) and the vent function is rather rare.

I'm grateful for your advice and input. Thank you!

 

[DRWeig]

Yes to IRstuff's comment, you really need a controller with a relay output instead of a simple on/off device.

Attached is a data sheet for one, REX C Series. Available on eBay for less than $30. You'd need to get the current-input model and configure it to use the relay output to control your valve. Then you'll configure your Ventostat to give you 4-20 mA out instead of 0-10V. Be sure and build your model number properly before ordering, though. You don't want to receive one that needs a temperature sensor hooked to it. Here's what I would buy if it were me:

C900 biggest one in size, easier to mess with
F reverse acting (turn the relay output OFF as CO2 rises)
8 4-20 mA input
01 scale range
M relay contact output
M second relay contact output (since it's in there anyway)
N N (no alarm outputs)

So Model C900 F 8 0-1 M M N N

You could change the two "N" characters to another code if you want alarming outputs (see pages 3 and 4 of data sheet).

You also get to choose the power supply voltage, 100-240 VAC, 24 VAC, or 24 VDC.

In my next post below I'll put the configuration manual.

If you decide to shop, go to eBay and put REX-C700 in the search field. Then try to contact a seller with the model number you need.

Or, I think FLW (

http://www.flw.com)

reps the manufacturer (no affiliation with me). But you won't get eBay pricing from them I bet...




Good on ya,

Goober Dave

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[DRWeig]

And here's the manual. Make some calls, I bet you have a friend-of-a-friend who can walk you through it.

Good on ya,

Goober Dave

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[MoonshadowXIII]

Dave -

Thanks for the info! I will do my research and see if I can find 1 of these units.
I am most grateful for your efforts. Thank you very much!

Cheers!
Moon

 

[MoonshadowXIII]

Just an update for you Dave....

So far I am having trouble locating a source for either the C900 or C700 with the specs you mentioned. There are an abundance of them with the "K" input, but the "801" is a bit more rare. I have a few emails out and am waiting for replies.

I did come across this unit -

http://atkinsonelectronics.com/manufacturing/product_pdfs/AVR1A.pdf

seems like it should do the job. Your thoughts?

Cheers!
Moon

 

[DRWeig]

The atkinsoneelectronics.com is very similar to the UCS-121 or UCS-221 mentioned earlier.

It's possible that you can experimentally determine the best points, but a controller is the absolute best solution.

Thinking back, the original Ventostats came with a 2-relay output as an option. They'd open the outdoor air dampers (fully) in a building when indoor CO2 levels hit 1200 ppm, then close them at 900 ppm (for example -- I think those were the factory defaults). You could choose your own setpoints as well.

Good on ya,

Goober Dave

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[MoonshadowXIII]

So far all my replies have been negative. One of the sellers I asked if they could get the C700 with a specific model# and the reply I got back was "it's 240v". Alrighty then!

So I found a UCS-221 on ebay for $25 + shipping. I think I'm just going to get that and wing it from there. Blowing on the monitor can cause a rapid increase in ppm reading, shouldn't be to difficult to calibrate the unit before I get too winded

Thanks again for all your help!

All the best...
Moon

 

[DRWeig]

Let us know how it goes!

Good on ya,

Goober Dave

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[OperaHouse]

Temperature controllers aren't always a problem. I am partial to the FUGI PXZ4 series PID controllers also sold as BIG CHIEF. These can be found on ebay fairly cheap. I bought a pair shipped to me for about $30 total used. A friend needed a high/low alarm for a pair of CO2/argon gas mixers for his weld shop. I just used a voltage divider into the temp input. The low side resistor has to be fairly low (under 100 ohms I think) to prevent open sensor alarm. I scaled it up so the correct gas mixture for each read 100% on the display and then set the upper and lower alarm limits 20% above and below that. The factory instructions are pretty bad as to set up. Once you play with it a bit they begin to make sense. Quite a powerful control and it sure saved time over building some comparitors. The voltage/current versions are rare and pricy used but the temperature versions are cheap and can likely be worked into many applications. I always keep a couple around.

 

[DRWeig]

I'll second the good words about Fuji PXZ4. Great product.

Good on ya,

Goober Dave

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[MoonshadowXIII]

RE: Fuji PXZ4

Cheapest 1 I could find on Ebay - $79.99 + shipping...... :/

 

[OperaHouse]

Like everything on ebay the Fuji PXZ4 appear in cycles. I've bought a half dozen in that price range. Besides if you want that deer in the headlight look just read the manual. I wrote my own document for programming them. If you don't use this stuff everyday it is like a new learning curve every time. I really like the Arduino UNO at only $16 for the China version and the development system is free online. Again initial setup of development system can be tricky but programming is pretty straightforward. Simple steps loke Read CO2 AD, if under turn on gas, wait 10 seconds, turn off gas, wait 10 seconds, loop to beginning. Lots of things you can add to it making it automatic. I just did a store display with an airplane with a 100 foot wingspan with one of these. I put a little solar panel from calculator on the top and read the A/D voltage. So the plane turns off at night when most of the lights are turned off. I think on ebay they even have CO2 monitors that plug into the board.

 

[MoonshadowXIII]

Wow... sounds like I would need to go to night school for a semester or 2 just to get it set up.
But thanks for input never the less. I saw somewhere in my Google wanderings a greenhouse automation computer system. But my goodness the price tag was out of this world! Orchids are just a hobby. Not going to spend thousands on a hobby. I built a 200 sf greenhouse out of old windows and mostly scrap I could scrounge up. Even after the humidity control system I pieced together and the latest investments in CO2 equipment I'm still coming in at under $500. Next I want to work on an automated drip irrigation system. This will be my 3rd summer with the greenhouse and it's really been a lot of fun setting things up and I have learned a few things along the way. My wife likes having fresh flowers for the table too, so that's a perk. I even started my tomatoes early this year in the greenhouse and transplanted to the garden at the end of May and they were almost 2ft tall. They are over 4ft now and loaded with fruit. Pretty cool!

Will post an update after I get this CO2 thing up and running (or sooner if I run into trouble).

Cheers!

 

[OperaHouse]

Everyone says....I just want it to do this. And that is NEVER a correct ststement. Once you start paying for gas you will decide to shut it off at night, then 10am to 4pm, then off when the exhausr fan comes on, then the misters. It never ends and it shouldn't end. As Demming says whatever you are doing now, no mater how successful you are it is wrong. Very liberating when you think of it. Many people from vastly different interests have been able to use the Adurno. I will be first to admit it, some will never figure it out. You likely don't even own a soldering iron or meter. If you could find some help getting started these little boards are really powerful. The greenhouse computer I found cost $1300. What state do you live in. There could be a market for a $150 board for the hobyist. Years back I was germinating plants with ultrasonics. Really interesting results.

 

[MoonshadowXIII]

Very true indeed!
I plan to use a timer on the CO2 so it doesn't run at night. I hadn't considered the exhaust to be a problem since it seldom gets triggered, but now that you bring it up I may have to consider a way to disable the CO2 while it's exhausting.... Yes I own a solder iron, can use it pretty well in fact. Years ago I worked in the Silicon Valley on an assembly line. Ever hear of the Koala? It was the precursor to the mouse (giving away my age now). But I can't read a schematic. I can identify components, read a resister (Bad Boys Like Our Young Girls But Violet Gives Willingly), but I have no clue how to put them all in a circuit or why one piece goes before another. Give me a printed board with a component list and a box of the pieces, I'll build the board for you no problem!

I live in the Northern California mountains. About 5000 ft elevation. The growing season is very short up here, hence my wanting the greenhouse. The set up so far has been pretty easy more or less. The temperature was easy enough to regulate, the humidity took a little more effort, have to run 2 monitors, 1 to activate the humidifier, the other to switch on the exhaust. I run supplemental lights in the winter months to get the hours of "sun light" up to 12 or better. Automating the CO2 has proven to be the biggest challenge so far. But I think (thanks to Daves help) I might have that beat... we shall see soon enough. And as I said before, the water will my next en-devour.

I would be interest in these boards you're talking about and how they can be used to make a computer automated system. I'm much better with computers than I am with electronics.

Cheers!
Moon

 

[OperaHouse]

Too far away for me to help.

For those not technically chalanged I would suggest the venerable LM431 Amplified Zener. Every engineer dreams of a three terminal solution and this is easy as it gets. Connect the cathode to a LED and relay to the plus supply. That can be up to 36V so great for 12 and 24V supplies. Use a small relay or just solenoid if less than 50ma. Most 4-20 ma devices can take a voltage burden of 3V. The control pin of the LM431 trips at about 2.5V so for ideal CO2 level. Select a sense resistance that approximates that with a small pot in series to add some variation or use a pot in normal voltage divider configuration. A LM431 can usually be found in an old PC power supply.