An interesting pipe dimmer project

[hellraizor]

Hello everyone! I am new here but have read around the forum a bit and like what a see. It seems like this is a very positive, helpful, and knowledgeable community. Which leads me to ask for some help.

I have been making lamps lamps out of galvanized pipe and want to add a dimmer to my lamps and use a gate valve as the dimmer control. I have seen it done before and will post a link to a video of one in action. In the video, you will notice that the person did not use a gate valve, but instead, used a 1 1/4" tee fitting with a gate valve knob retrofitted.

The mechanics of it are not hard for me to understand, however, what rotary style dimmer would fit in such a small area is what is preventing me from completing this endeavor. Any help, suggestions, or comments are really appreciated. Thanks! Here is the link to the video I referred to.

 

[(*steve*)]

Given the limited movement required to control the lamp, I suggest that the shaft of the potentiometer in a normal lamp dimmer has been attached to the valve.

Dimmer circuits are pretty simple, and (for the suitably skilled) would not be hard to make to fit in such a space. Commercial units, as I'm sure you've noted, tend to be compact rather than long and thin, but that's typically to fit the enclosures they're expected to go into.

 

[hellraizor]

Yes, he did in fact use liquid steel and a metal rod. My issue is, what kind of dimmer would fit inside of the pipe?

 

[hellraizor]

Or how would I go about engineering one to fit inside?

 

[KrisBlueNZ]

Find a design for an incandescent lamp dimmer using a triac - you'll find plenty with a Google search - and choose components that will fit inside the pipe.

There aren't really any large components in a typical dimmer. There are some inductors for interference suppression, the triac itself, and the potentiometer.

I suggest enclosing the circuit in potting resin or similar, so it can be easily slipped into and out of the pipe. For example, make it a long thin cylinder, with the AC mains wires entering at one end, and at the other end, have the two wires that go to the bulb and the two wires for the potentiometer. Then you can slip it into the pipe below the valve.

You need to be extremely careful to ensure that nothing, including the potentiometer terminals, can make contact with the pipe. Also, with all that exposed metal, and a potentiometer, I don't think you could claim double-insulated status, so you need to earth the pipe and use a 3-pin plug. If the pipe was not earthed, it would be illegal in my country at least, and dangerous in any country.

 

[hellraizor]

Would something like this work? http://pages.ebay.com/link/?nav=item.view&id=231109567285

 

[KrisBlueNZ]

Electrically, it's probably OK. Mechanically... only you can say.

I don't recommend buying cheap, unknown-origin products from eBay, especially for AC mains-powered applications. They can have problems with safety, reliability, interference... generally, standards-compliance.

Edit: It looks like that "Leviton" unit is UL-recognised. If the UL logo is genuine, then at least it should be safe and reliable.

 

[hellraizor]

What would you suggest as an alternative? I don't particularly like the plastic post on the dimmer I linked to. It's bound to end up broken.

 

[(*steve*)]

Given that your choice of control is something that people grab and twist with force, I would recommend that you engineer it so that the valve control itself has hard stops that prevent a ham-fisted person from damaging the dimmer control.

 

[hellraizor]

Stops is a definite good idea. As far as the engineering of this dimmer goes. What parts should I be searching for? A triac? A potentiometer? I know I cant run a potentiometer alone. Sorry, but I have no idea where to start as far as putting this dimmer together myself.

 

[KrisBlueNZ]

http://www.google.com/search?q=triac+dimmer
Google is always a good place to start

 

[hellraizor]

What about something like this? http://www.ebay.com/itm/ZE-03-Lamp-...20VAC-Replacement-or-Repair-Kit-/170972623332

 

[hellraizor]

Thanks. I found a decent video showing how to put one together. Ill have to see how cost effective it is but it does seem more versatile

 

[KrisBlueNZ]

What about something like this? http://www.ebay.com/itm/ZE-03-Lamp-...20VAC-Replacement-or-Repair-Kit-/170972623332

I can't really tell. There's less information than the previous one! It looks too big though. And the advert doesn't mention any safety certifications.

 

[hellraizor]

Yeah, I will probably try putting together my own triac dimmer and see how it goes. Time to learn how to read schematics and solder to a board!

 

[hellraizor]

Ok so my plan is to build the board and mount it inside of the tee fitting, the potentiometer will be mounted to the board using wires so I can extend the pot to the other opening of the tee and have the post sticking out and mount the gate valve handle directly to the post using jb weld. Now, what can I use to mount and insulate the board inside of the metal pipe? I obviously don't want people getting electricuted. Thanks for all the help. I really appreciate it.

 

[KrisBlueNZ]

In post #5 I suggested potting mix.

 

[hellraizor]

Ah yes, I'm sorry, I missed that. Thank you so much for all your help. I just ordered the parts I should need for this and am really looking forward to making this happen.

 

[(*steve*)]

Now, what can I use to mount and insulate the board inside of the metal pipe?

Place heatshrink tubing around the completed circuit, then place it in a plastic tube to provide another layer of insulation between the circuit and the pipe. Make sure it's a loose fit in the pipe so nothing is squeezed in place.

And earth the pipe!

 

[BobK]

In post #5 I suggested potting mix.

Don't ask your wife to buy the potting mix. If it were my wife, I would definitely get the wrong thing

Bob