Suggestion on lights

"George" wrote: (clip) Alternatively, suggestions on how to wire one? ^^^^^^^^^^^^ To me, the obvious solution would be another HF unit, but this time add a muffin fan. Since it survived for six months, and then failed only after eight hours of continuous use, it seems marginally OK. Just a little additional cooling should make it last a real long time.

Good idea, Leo. Another would be to use one HF dimmer for each 500 watt light.

I would use a commercial 1000-1500 watt dimmer and wire it into a box, but they cost $50 and up, probably more by now. Using something that might melt down in the future doesn't sound like an option to me. A Sylvania rep told me that halogen bulbs should be brought up to full brightness before being switched off, if you're using a dimmer, or the life expectancy of the bulbs will be shortened. Why not add a smaller halogen light and simply vary the number of lights you're using? The color temperature seems to suffer when you dim halogen lights anyhow, they get kind of yellow.

Out of curiosity, what would be wrong with wiring a plain old household $5 dimmer switch to an outlet?

If the OP is the sort of person that can wire together 4 electronic components safely, using rosin (or other non-acid core) solder, and who doesn't care about RFI or "snap-on" at low brightness levels, it's not hard to make a phase control good for many amperes.

Eg. Q4040K7 @7.13 ea. 1-off 40A/400V Alternistor HT32B @0.25 ea. 1-off 32V diac

Plus a 250K pot insulated well enough for line voltage and a 0.1uF film capacitor that could be scrounged (eg. out of a regular dimmer)

A nice big fat piece of of aluminum could serve as a heatink. The TO-218 package is electrically isolated from the mounting screw but care still needs to be take to insulate the leads from accidentally touching the case.

OTOH, if he's going to hurt himself or someone else or cause damage, better not to ask..

Best regards, Spehro Pefhany

If I'm given a wiring diagram and a list of part numbers & vendors, I can manage. I'm just not an electronics guru. Years and years ago, I did circuit board component level repairs but it was take part X, test it, find part Y that is damaged, remove Y, solder in Z and test again. For example, I don't understand the slang you are using below.

Do you have any websites/schematics?

Have a look at PDF page 4 (figure AN1003.9)

It shows only a 10A triac, which isn't nearly good enough for this application.

The Q4040K7 (40A triac) data is here:

The HT-32B (diac) data is here, the HT-34B shown in the schematic will work as well.

You can get the two oddball* parts plus the below-mentioned fuse (and a fuseholder if you need one) from digikey.com (who have a handling fee for less than about $25, IIRC) or mouser.com, which has no handling fee, but doesn't stock the triac, but does carry an NTE equivalent for about $1 more.

• you probably won't find a separate diac in a modern cheap dimmer. They often package the diac and triac together in one package.

There will be about 15 Watts to get rid of, while keeping the part as cool as possible, so you'll have to bolt the TO-218X package (dimensions in the above data) down to a thermally conductive heat sink (a length of aluminum channel etc.) with a bit of heat sink compound under it. Be sure to place some insulating material so the leads can't ground out to the channel. Be sure to ground the channel or whatever heatsink for safety. Steel isn't very thermally conductive. Fuse with a 15A ABC-15 ceramic fuse in the hot line. The triac will then have a fighting chance of surviving the inevitable lamp failure.

If you're not sure about it, please get someone local who is knowledgable to help you.

Best regards, Spehro Pefhany

Thanks Spehro, I'll dig in and check things out.

--George

Aluminum single-gang "Bell Box", 1000W store-bought light dimmer, weatherproof cover that fits over dimmer handle, 2 "cord grips" for in the box to fit the cord on the stand light, and two 300W lamps.

Put cord grips on ends of box, use silicone. Cut cord for light stand and strip sheath on each end 6". Place in the cord grips and tighten. Splice neutrals through, splice grounds and attach to ground screw in box. Connect and mount dimmer, mount wet cover. Attach the box to the vertical post of the stand with an appropriate clamp.

And change out at least one of the 500W lamps for a 300W, if not both - you have to leave some slack in the dimmer ratings, plus the lampholder ends in the fixtures will live longer under the reduced heat load. If you have 1000W of total load on a 1000W dimmer, one lamp burning out while it is on will kill the dimmer.

1000W dimmers are expensive enough, you don't want to price anything heavier. And don't try using two 600W dimmers (one for each lamp) unless you put them in separate boxes - gang two of them next to each other in one box and they have to be derated to 500W each.

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I bought 2 of the HF router speed controls SKU #43060 about a year ago, and when I removed the back panel of one of them, one of the soldered wire leads separated from the circuit board. I always open any new electrical electrical equipment from China, since the connections are nearly always unreliable. I ended up resoldering everything in both units, and checking that everything was insulated properly. The pop rivets still had the tips of the stems in them, and they pushed out easily with an awl.

For continuous use, it would most likely be beneficial for reliability to replace the rear panel with a grounded finned heatsink (about the same size as the box), with heatsink compound under the triac. With a lot of this cheap stuff, it's often wiser to find a better grade of equipment.

WB ...............