YO, EEs!

[cx]

A Q for youins EE types, or any knowledgeable mortals, for that matter:

Built that fine greenhouse whereof I posted a picher a year or so ago. Has an exhaust fan on one end, and a "water wall" on the other. Water wall has a motor-driven open-out louver on the outside. Fan and motor are operated by a single thermostat. 99+ percent of the time, when the fan comes on the intake louvers open just fine. Now and then, usually when there is a slight wind against the louvers, the fan spools up before the louvers can open and sucks them shut. Very bad. No air gets in. Much sun still gets in. Plants maybe die. CX looks really bad. :(

I can't find a simple, fixed time delay that I can put in the motor circuit so's to give the louvers a head start. In my WW Granger catalog there are all sorts of delays, but all the ones with sufficient load rating are waaaay more complex than I need, and the fixed ones are much too lightweight.

So, how do I make a simple, fixed, in-line delay that will handle a 1/3 hp (I think) motor and give me a delay of, let's say, maybe a second or a little less? More would be OK, too.

Or where would I shop for one?

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[Sonnie Layne]

CX,

Finally, a subject I can offer assistance with! I don't want to bore you with too many details of the 100+ acres of HVC that I've dealt with in the greenhouse industry, so I won't.

First things first... what plants are they trying to maintain and what is their first priority? The specific plants that are the most important to them will determine what we do with the temps.

Some plants do better with cooler day temps than night temps. Not possible in TX without refrigeration coming into the recipe. That's not a common issue, however. If they want to maintain a stay of orchids/bromeliads from south of the border, the task is simple. If they want to keep potted asparagus in production throught the Texas heat, it's another.

Outline... be patient with me, I'm listening to Shania Twain and having my Martini...

Attach the water pump and the louvers to one thermostat. The fans are another world. Actually, in TX, I'd have a dual stage thermo for the water/louvers, then a single stage for the fans, given the size of the greenhouse as I remember it. Keep in mind I'm used to dealing lastly with greenhouse complexes of 10K sqft or so, but I've also had a dozen or so hobby houses in the south.

Unless there are exotic spp. of plants cared for here in the conservatory (yes, you're allowed to use the term, if plants are being saved from destruction), the shutters could be locked on at this time of year. In the remainder of the year, when temps drop below critical at night, a dual stage thermo will allow you to offer three stages of cooling...

First, the vents open on one leg of the dual thermo., then the fans kick on, then the water starts flowing. Man, if only our houses could be that great, huh?

Basically, in TX, unless their collection is really cool (in which case I'd like to see it personally), the louvers are open all day and night. When the secondary temp rises, say above 80, the fans come on (they'll likely stay on all summer), then if the temp rises above 83, the water kicks on. That way, the louvers should be on and not be blown shut.

Another way to deal with it is a more mechanical thingy. As the louvers fully open, have a mechanical switch turn the fans on, then let another thermo turn the water on, or a secondary stager of the mechanical limit switch.

Tip... cooling started 30 min before sunrise has a surprising effect on phytocompatriates. Then let it warm up. Kinda like the song... coldest hour is just before dawn......

all that's another chapter. Hope this helps. I could possibly lend more if needed.

all my best, Sonnie

PS... tell 'em they're not gonna duplicate Costa Rica in Austin without droppin a few bucks in insulated block walls. I've done it, but the clients had bucks. Also, for some specie of plants, downdraft is an issue for ultimate production. Especially if they're into getting blue ribbons in the local Orchid society (which I was a judge in LA and a photographer in the American Orchid Society, associate writer in the Bromeliad Digest, Southern Horticulturist.

On the other hand, if they just want to have some good stuff to look at, let them know how to get to me. I'll help you with the physical plant, but it's the horticulture that nowdays really attracts me. Primarily 'cause I can't have it where I live. There again, I can always find a way to pick a spot amongst the primary form of life on the planet.

We ain't even started to talk about daylengths or humidistats yet... we're still in the third grade. :D

[jjwq8]

Sonnie,
Salaams to your obvious expertise, but you might want to think about listening to your martini and having your shania :D

We faced a similar problem on a shopping mall with a central atrium that was more like a forest.

Quaint solution. smoke ventilators were doubled-up. Half to fulfill madatory smoke venting regs other were for the plants.

These were motorized dampers as against the magnetic release type. The motors were operated by a simple photovoltaic cell.

Sun she rise, come roun de erf nuff to put rays on cell and poof, plenty fresh air.

No admittedly this was tied back to the BAS system but something similar may help.

If cx neighbourhood is typical of the rest of the south-west then clunkers and junkers litter the road-side. Open up one of the doors and grag yersel one o'dem window lift motors then go to your local hobby shop and get a small 12v step down transformer and there you got your motor. Visit ACE hardware get a couple (?) of alu window brace hinges and a length of 10mm dia alu rod or thick wall tube and some pop rivets and you got yersel a actuator too.

If the car jacking method doesn't appeal or Mrs cx objects and wants a proper job then look at Colt (not the hand guns) or some other espenive kit.

[John Bridge]

Link to said greenhouse. :)

http://johnbridge.com/images/kelly-greenhouse.jpg

[cx]

Mmmm, no response from no EEs. Maybe too many injineer jokes? :(

Sonnie and Jeremy:

Thanks for the input, but neither answers my question. :)

All the engineering and construction are long since done, Sonnie. I've got only two stages of cooling: fan and fan plus water. No passive ventilation; building was too small to take up space for another big opening. I have separate thermostats for the gas heater, exhaust fan, and water pump plus intake louver. I have it set up so the fan comes on at 85 or so, and the water wall comes on just under 90. That also lets the fan stay on after the water goes off so the water wall pads can get dried out, which the manufacturer thinks is a good idea.

Local greenhouse guy said he puts a separate, remote reading thermostat on the louvers that basically keeps them open all year until it gets real cold. Didn't want that for a number of reasons.

Anyway, I've got what I've got, I just want it to work better. Your idea for a switch on the louver to activate the fan is something we though about and rejected; didn't want one more switch in the wettest, most hostile area of the whole beast. Still don't want any more relays or switches in there anywhere, which is why I'd like something solid-state if possible.

Don't need a motor, Jeremy, already got one of those. Need a time delay.

It's about 24 feet from the exhaust fan to the intake, which I thought would be far enough, and provide air volume enough, not to have this problem. But nooooo.

So for now I've just wired the louvers open. This will get me by for some months, but I really want to fix the problem as soon as I can. I like bein' the hero better than bein' the goat, eh? :p

[Davy]

Better not be any wacky tobacky in that green house.:D

[cx]

These are most respectable customers, Davy! :mad:










How would one recognize such tobacky plants? :D

[davem]

Sorry I missed this till now Kelly. Have a looky here:
http://oeiwcs.omron.com/webapp/commerce/command/ExecMacro/Omron/macros/itemdisp.d2w/report?prmenbr=316&prrfnbr=3957

If you like, it can be had at digikey for $37.11
http://www.digikey.com/scripts/us/dksus.dll?Criteria?Ref=137901&Cat=32900173

Only thing is the spec sheet says 85% relhum limit. Don't know what happens if it goes above that.

[cx]

Thanks, Dave.

I looked at a similar (don't recall the brand name) unit in WW Grainger's catalog. I was really trying to stay away from anything with exposed contacts and such, precisely because of the humidity problem. I'm sure that place runs above 85% most of the time, or at least it seems that way every time I've been there.

I suppose if I mounted it way up near the exhaust fan, she at least wouldn't water it as often as I bet the thermostats get. :)

I was hopin' you would just tell me how to make a fixed delay with no plug-in type connections or moving parts that I could just stuff into the fan connection box. Oh, yeah, that's what I was hopin'. My electronics learnin' was waaaaaa to long ago to remember how one might attack that. :(

I shall keep that one in mind, though. The price seems like it's a couple bucks lower than Grainger, and my Grainger catalog is a 1996 model. :eek:

[davem]

You looking for a home brew solid state time delay relay. That's all? :D

I'm a little rusty too. I'll see what I can do. :)

[cx]

Well, either that or tell me how much longer the war to the fan would need to be so's it'd take them little electron fellas a second longer to arrive. :shades:

I figgered one of youins EEs would kinda know right off the top of your head. You know, little bit R, little bit L, maybe some C, pewt'em inna bag and shake'em and presto! one second delay. No?
:p

[davem]

Where do you propose to put them bitsies? Maybe I can send you a little baggie of parts and you can do a little mojo dance in front of that fan? :D

[kemguru]

http://www.accesscontrolsales.com/catalog2/tgc.htm

[cx]

Thanks, Tim. That's closer, for sure. Similar ones I've seen were all for much lighter loads than I need. Maybe I could solder to their terminals, epoxy over the switch panel, and have a semi-sealed unit.

Problem is, them's Canucks. Reckon their electrons are the same as our electrons? :)

I'll give'em a call.


I can pewt'em all together, Dave, but I don't do no dancin'. :D

See that little box Tim linked? Somewhere in there is just what I need, without the flexibility of all them switches. What is it? :confused:

[kemguru]

http://www.accesscontrolsales.com/catalog2/tgc_cube.htm

Without the dip switch.

The delay is digital CMOS, completely enclosed on all units, even the switch units. Made specifically for harsh environments. Little 2" x 2" box.

Or hide a full spool of wire somewhere:D

[davem]

:bow: I owe you one Tim. :D

[cx]

Is this a great site, or what?!! :):)

Where else on this wild wild web can a fella get electrical advice from a chemist, computer advice from and electrical injineer, woodworking advice from a mud man, bullshit from a small-time home builder, and soooo much more? Gotta love it! :D

Thanks, Tim, that's damn close. In fact, if it had wire pigtails stickin' out instead of push-on terminals, I'da swore I designed it myownself. Now I just gotta figger out how to buy one - and how bad that's gonna hurt. ;)

Dave: With nothing more than changing a load resistor value to change the time constant, I know in my heart of hearts that in your engineering brain right now you're seein' a picher of that circuit. I know you are. Remember when you studied that in the big school? :idea:

Anyway, one of those that Tim posted is plenty close enough. I just wanna remember what that circuit looks like. Hell, man, I learnt that stuff in 1963, your schoolin' is a little more current than that, eh? :stick:



OK, OK, so you can get the bullshit from a builder anywhere, the diversity was my point. :rolleyes:

[jjwq8]

CX

is a diversity, one university plagiarizing another? :D