Need Electronics Help

[lycaonpictus]

I'm looking for a piece of electronics that I'm not even sure exists, but figured you folks would know if anyone does!

I have a large wardian case (roughly 2' x 4' x 5'). Built into the case is a system whereby a humidistat on the top of the case controls whether or not a fogger + fan arrangement turns on. Below ~50% humidity, fogger and fan turn on, blow fog all around the inside of the cabinet; when the humidity gets up high enough, the system turns off again.

This is a homemade case (not by me, and beautifully done, but still not "professionally" manufactured). Right now, the cord for the humidistat is spliced together with an extension cord, into which the fogger + fan are plugged. Basically, the humidistat is working as a switch, which allows current to flow or not to the extension cord.

Now, I was a little leery of this splice when I first got the case, but it seems to work all right. Still, I've been meaning to see about doing something more durable / safe.

This weekend, the electronics associated with my case had a minor meltdown. I knew I had too much stuff plugged into a couple of outlets, but for the first time I started having some problems with blown circuits, etc. (No fires or anything! Just stuff complaining about the conditions.) So this weekend was spent wiring in two brand new outlets -- each on their own independent circuits! -- and I'm looking at re-setting up the various electronics for the case. Now seemed like a good time to address the issue of the splice for the humidity system.

It seems to me that there should exist a sort of switch box that does the job of this splice -- something that the humidistat tells to turn on / off, which is what the fogger + fan are plugged into. Thinking about it now, I guess that's the job being done by the extension cord. But it seems like there ought to be something more official that would be a better, safer option than just splicing an extension cord into things.

Anyone have any ideas? Suggestions? Thanks!

L.P.

[Discus]

Step one, if you're worried about safety, GFCI/RCD.

The gadget you're looking for with regard to the switching is called a "relay", although your humidistat *is* a relay, effectively. If you're worried about the wiring being a bit dodgy, build a small plastic case with a muffin fan blowing through it inside which your humiditat and splice(s) live.

If you get a relay, effectively, you want the output of the humidistat to turn the relay on - this is called a NO (normally open) relay.

[lycaonpictus]

Excellent! Thanks for the info, Discus.

I'm not worried about wetness with any of the electronics. With the exception of the fans I use for air circulation, all the electrical stuff is OUTSIDE the case, including the dodgy splice. So it was more being suspicious of a wad of electrical tape around a carved up extension cord that had me going, "Hmmmmm."

Thanks again! This at least gives me somewhere to start looking.

L.P.

[Discus]

Exactly how you wire them up depends on the model you get. Wire the humidistat so it energises the coil on the relay and turns the current on. I was about to sketch something and realised it wouldn't really help you at all without knowing the exact components you were using. Generally, you use the gear to switch the live (hot) pole and run the neutral and earth straight through. Using small bus bars makes things neater when you do the wiring.

I actually have the components lying around to do more or less what you're trying to do (along with automating my lights with the sun's input for light supplementation), just haven't gotten around to the build

On thing that is nice about relays is you can use them to switch different voltages and/or currents for items that can't handle it. (i.e. fi you use low voltage sensors but need to switch mains voltage).

In general, where possible, it's best to keep things low voltage when near water/humidity, and make damn sure your earth is good. If you have metal in there, ground it!

Some handy links:
Residual-current device - Wikipedia, the free encyclopedia
Relay - Wikipedia, the free encyclopedia

---------- Post added at 05:10 PM ---------- Previous post was at 05:07 PM ----------

Oh, well, if you don't like the electrical tape splice, get a small plastic "project box" and some of those "chocolate block" terminal connectors and/or small bus bar(s), depending on what you need to wire and what you like the look of.

Peel the tape off the splice (UNPLUG IT FIRST!), see where the wires go. Put one end in through a hole in a project box (preferably through the right sized rubber grommit), then cable tie it on the inside to stop it slipping out. Ditto for the wire going out. Connect the wires up again as they were in the splice, using terminal blocks or bus bars. If you're not sure, sketch the thing out noting wire colours and what is connected to what before you undo anything.

Properly done splices are fine (safety wise), they just look a little untidy. You can even get resin casting blocks specifically to cover a splice in a hunk of resin - totally waterproof, and somewhat neater than tape.

If you don't like electrical tape, self-vulcanising rubber tape is awesome, but it will still look "splice-y"!

[lycaonpictus]

Discus -- I'm coming here with all my electrical questions from now on! :LOL: Thanks for all the great input. This gives me a lot of stuff to investigate and consider for purposes of improving my splice. I'll let you know how it goes!

L.P.

[Discus]

heh Good luck.