variable speed rheostats as 1K dimmers

N

nickbeef

Active member
I noticed a few mentions on this board about using variable speed rheostats as 1K dimmers. Searching on ebay I noticed that these rheostats run for about $20 each, while dedicated 1K light dimmers go for around $50 or so. Does any one know if there any practical difference between these devices or are they the exact same thing in different housings, marketed and priced for different industries?

I know different makes and models will be of different quality, but all the rheostats on ebay appear to cosmetically be exactly the same as some of the "1K light dimmer" also sold on ebay, but again priced differently.
 
Many people have used them, I would be cautious about putting a 1k load on one though. A dedicated 1k dimmer has a much larger heat sink, those speed controllers are meant for power tools which are never continuously on like a light would be.

Wait for a Lutron dimmer to come up for cheap on eBay, I paid 99 cent plus shipping for one of mine plus a few bucks at Home Depot for the plugs and gang box.
 
Check out this item I found on eBay: http://pages.ebay.com/link/?nav=item.view&id=161193946122&alt=web

Rheostats are a the old way of dimming. The ones above use a modern switching Triac. These can handle up to 4Kw.
And will be fine even running smaller loads. I'm putting them into an metal enclosure may up the size of the heatsink if required.
Also adding an LED indicator, flash switch and replacing the potentiometer with a slider.

Surinder.
 
I'd be more worried about rf noise than heat. Most theatrical dimmers have large chokes for that reason.

surinder said:
Check out this item I found on eBay: http://pages.ebay.com/link/?nav=item.view&id=161193946122&alt=web

Rheostats are a the old way of dimming. The ones above use a modern switching Triac. These can handle up to 4Kw.
And will be fine even running smaller loads. I'm putting them into an metal enclosure may up the size of the heatsink if required.
Also adding an LED indicator, flash switch and replacing the potentiometer with a slider.

Surinder.
Click to expand...
 
Moseph, if I use a household dimmer and build my own (which I've done before, but only 500w), wouldn't that have no heat sink whatsoever? Do they operate using different mechanics? Or are they the same thing?

For what it's worth, BarnDoor Lighting Outfitters sells two types of 1K dimmers. The cheaper motor speed rheostat dimmer at $32: http://www.filmandvideolighting.com/10vadi.html

and the more expensive rotary dial household dimmer at $99: http://www.filmandvideolighting.com/di10horo.html

That's quite a price difference. The "rotary dial household" dimmer seems to be just a standard household dimmer pre-assembled, so I'm not sure what justifies the price. Perhaps it has a more robust heatsink? The variable speed rheostat also comes with this disclaimer in the description:

"**Router speed controls are used in short duration. This unit, used as a dimmer, is not designed to be used for extended periods of time."

I'm ok with using it in short intervals, but I would be more concerned about noise or buzzing that you guys mentioned. Then again, all tungsten lights buzz when dimmed down, right?
 
surinder said:
Check out this item I found on eBay: http://pages.ebay.com/link/?nav=item.view&id=161193946122&alt=web
Rheostats are a the old way of dimming. The ones above use a modern switching Triac. These can handle up to 4Kw.
And will be fine even running smaller loads. I'm putting them into an metal enclosure may up the size of the heatsink if required.
Also adding an LED indicator, flash switch and replacing the potentiometer with a slider.
Surinder.
Click to expand...
Between the tiny little terminal blocks, the fact that it's all on a PCB, and the tiny heat sink, I don't know how it's physically possible for that device to handle 4000 watts. If you can solve the mystery I'd love to know about it.
nickbeef said:
Moseph, if I use a household dimmer and build my own (which I've done before, but only 500w), wouldn't that have no heat sink whatsoever? Do they operate using different mechanics? Or are they the same thing?
For what it's worth, BarnDoor Lighting Outfitters sells two types of 1K dimmers. The cheaper motor speed rheostat dimmer at $32: http://www.filmandvideolighting.com/10vadi.html
and the more expensive rotary dial household dimmer at $99: http://www.filmandvideolighting.com/di10horo.html
That's quite a price difference. The "rotary dial household" dimmer seems to be just a standard household dimmer pre-assembled, so I'm not sure what justifies the price. Perhaps it has a more robust heatsink?
Click to expand...
The second thing you posted contains what I was referring to, a 1000 watt household dimmer. These have a decent sized heat sink built in and usually retail for around $60. I'm surprised they're not selling it for more.
nickbeef said:
The variable speed rheostat also comes with this disclaimer in the description:
"**Router speed controls are used in short duration. This unit, used as a dimmer, is not designed to be used for extended periods of time."
I'm ok with using it in short intervals, but I would be more concerned about noise or buzzing that you guys mentioned. Then again, all tungsten lights buzz when dimmed down, right?
Click to expand...
Unless it's on a variac, pretty much. Don't worry about it till sound complains, which hardly ever happens. Most locations and even stages just aren't quiet enough for him to hear it.
Believe me, you want something you can leave continuously on. Shutting off your light between takes because of a subpar dimming mechanism is no way to shoot anything. If you're only using it for a 650 it should be fine though.
 
You must log in or register to reply here.
Back
Top