Toroidal transformers

[Daemon]

Hi all

I have read the forums a few times and my question does not seem to be answered.

I got a bit of a deal on some 400va toroidal transformers but they are 230v to 28.5-0-28.5. Approx 5v per secondary

So I need to reduce the voltage a little bit. I have wired the secondaries so they are in parallel so I have 230v to 28.5v @ 10 amps.

I was going to unwind the secondaries a little until it tested at a little over 24v but sometimes apparently the secondary windings are on top of each other.
(I havent received the transformers yet, they are in the mail)

How would you guys handle this?
Would you increase the primary winding to decrease the output voltage, use a variac on the input, use a triac or resistor on the output or other.
Would you rectify the voltage to dc?

Just wondering, and although my post may sound like I know what I am talking about, I dont really so please use really little words and spell it out in electricity for dummies language for me.

And try to avoid telling me that electricity kills, because I know that one. :)

Thanks all

[synnie]

Easiest way Daemon would be to use a resistor or something on the output, not by playing with the windings.if youre using Incandescants it probably wouldnt be a major issue with the voltage. If you rectify the voltage to dc then remember that 24VAC is equal to 33.6VDC due to DC voltage being 1.4 times greater than AC voltage.
Kamahilights could help you there with being in the area, would know which parts needed and best place to source them in your part of the world
Cheers Syn

[awhaley]

Well, in addition to killing, electricity hurts really bad. :P

What are you trying to do with all of this once it's set up? Are you just trying to drive 24V light strings off of 230V power? I agree with Synnie that 28V will probably not destroy 24V incandescents, but it may shorten the lamp life...

How much current are you actually planning to pull down the line? Any simple and cute way to drop those last 4 volts after the transformer will depend on the current being pulled...

If I were going to modify the transformer, I would think unwinding would be easier than winding, assuming that the wires aren't intertwined or glued down... The primary on your transformer should have roughly 8 turns to every 1 turn on the secondary and you want roughly 9 to 1 to get 220 to 24V...


Art

[Daemon]

Hi Synnie

John is helping me out and is being rather patient too! I just thought I would question to see if anyone had a simple solution I hadn;t considered.
My intention is just to run incandescants.

And thanks Art, I will keep in mind that electricity really hurts. At no time during my elctrical work will I put my tongue on 2 contacts to see if they are conducting current.

[djulien]

My intention is just to run incandescants.

Could you just add a few more bulbs in series? For example, take a 100 ct. string and chop it up into 2-, 3-, or 4- bulb segments (use the appropriate number of bulbs to get the voltage drop you want). You could fine-tune the voltage or brightness by adding or substracting bulb(s). This would also give you a few more lights, rather than just generating heat aith a series resistor.

don

[synnie]

With the Aussie and im going to assume Kiwi lights they are low voltage so you might have a string of say 200 lights, but it could be made up of 20 sections of 10 bulbs, each bulb being 2.4 volts.depends on who the manufactirer is, i have strings with sections of 20 bulbs.

[awhaley]

I wouldn't judge you for tasting for low voltage. ;) I used to know a guy who could kind of function as a human voltmeter... he could tell you within about a volt what he'd just touched to his tongue... anywhere up to about 24 volts he claimed. Now, I don't think I want to shock myself enough times to calibrate my internal scale... nor do I want to be there the day he tastes a 120V wire accidentally....

Art

[Daemon]

John is going to have a look first, I will send one to him and see if it can't be unwound a little. If it turns out one of the secondary windings is under the other then I will take the option of adding lights to it for a voltage drop.

Thanks everyone.

[Daemon]

Hi all

I never sent one to John in the end. He had a look at photos by email and I unwound a few turns off them following his instructions. It wasn't a difficult thing to do in the end.

Now I can just work on mounting them and adding fuses to the output.

Thanks

[Daemon]

WOuld someone be kind enough to post a few photos of their toroidals and ssr's etc.

As in, what everyone has done to mount and connect the toroidals to the ssr's.

My plan is to put a toroidal and 4 ssr's into a waterproof enclosure.(x3)

I am a backwards child so I am probably doing things wrong but I intend to have a 230v power chord and 12 network cables leading out from my controller box to each enclosure and then wire directly into the toroidal transformer.

If anyone else has toroidals in an enclosure or can show me some photos of the output from the secondaries going to the ssr's and then onto the lighting then I would appreciate a look.

Thanks
Daemon

[toodle_pipsky]

I thought I had more notes on transformers . . . but I don’t, only a few hand scribbled notes and a photo from the Melb Mini last year.

Anyway, the transformer I have is a 240V to 12V – 12V, so connecting it the way I did meant I got 24V (which is connecting it in series). The white output was connected to the lights, the red was connected to the appropriate board (in my case a Ren-16 and a few SSRs). I also have a 18V-18V transformer wired to run 36V. I daisy chained the power for those.

I put together a little spreadsheet to help me work out how much load I was running – really simple, just the specs from the original wall plug, added that up and took that from the specs of the transformer. I also used the watt meter in Vixen to get an idea of how much juice the lights were pulling to make sure I wasn’t going over the transformer’s specs.

My plan this year, if I’m organized enough, is to put the transformers in a nice enclosure and keep that part inside. What I will then do is run the power out to all the points I need, so far that’s 2 different places in the yard, by way of an extension cord. I can then “organise” the power as needed inside waterproof enclosures by way of screw terminal strips. I also plan on using the fused plugs I never got around to using last year.

Hope this helps! I'm not posting a picture of mine because it was an absolute mess and not what I wanted at all. Just a big wad of wires, that's what I get for rushing and leaving things to the last minute. But hey, first year, everything was from scratch! The picture of the Ren-16 is not mine, it's what I used to work out how to connect mine (after I fudged the first one I bought - I still have it sitting on my desk to remind me I'm an idiot).

Also this is a very useful diagram http://www.diylightanimation.com/wiki/index.php?title=LVT

[Daemon]

Thanks very much for that.
Much appreciated