An interesting pipe dimmer project

[hellraizor]

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

Bob

Haha I thought he was being sarcastic until I reread the post as I'd never heard of potting mix/resin lol

 

[KrisBlueNZ]

LOL Sorry for the confusion!

Steve's suggestions are a very good idea. Make sure there is LOTS of insulation between the circuitry and the pipe. After you've enclosed all the parts in potting mix, add one or more pieces of heatshrink tubing or plastic tubing around it all.

What's the internal diameter of the pipe? It's going to be a bit of a squeeze...

 

[hellraizor]

It is almost exactly 1 1/4". It'll be a challenge but hey that's half the fun.

 

[hellraizor]

Ok. So I went online and looked up some stuff. I found this http://www.aaroncake.net/circuits/dimmer.asp the only change I think I am going to make is to change the lamp to a diac on the board. From what I've read, it seems like a better idea. So, since I've never done this before and don't really know how to read schematics or what gets soldered to what I ordered this dimmer

so that I could try to see what is soldered to what. My potentiometer won't be mounted directly to the board, it will be mounted with wires so that I can put the pot where I need it. Here is the back of the board with the soldering points

I have not gotten the dimmer in yet but I do have a question. On this example, do the light green areas of the board act as traces for the the electricity to flow or are they just a guide for the manufacturer? I'm sorry, I just have no idea when it comes to PCB's. If anybody wants to take the time to look at the schematic I posted and maybe put a picture together of what gets connected to what, that would be amazing. Otherwise, I will just wait til this dimmer comes in and try to figure it out myself. Again, thanks for any help, you guys have been awesome.

 

[BobK]

I think I am going to make is to change the lamp to a diac on the board. From what I've read, it seems like a better idea.

The lamp, in the circuit diagram you linked, is the lamp being dimmed. I don't think you want to change that to a DIAC.

Bob

 

[hellraizor]

The part designated L2 is a neon lamp on the board. I will post a video that the guy put up showing the board in action.

 

[hellraizor]

Here is the video of the board in action. He highlights the lamp on the board

 

[hellraizor]

L1 on the schematic is the light that would be controlled

 

[KrisBlueNZ]

Yes, the light green areas on the solder side of that circuit board are areas of copper that connect the components together.

You're right. L2 is a neon bulb and you can replace it with a diac, but a neon bulb has a breakdown voltage of about 90V and diacs usually have a lower breakdown voltage. So you will probably need to change the values of the other components to get a full dimming range if you use a diac instead of a neon bulb.

If you reconstruct the circuit of that board you've ordered, using the components from the board, you'll get the full dimming range. That's assuming that board gives you the full range - you should test it before you dismantle and reconstruct it.

Also, you should use an inductor in series with the mains input to reduce the amount of interference back-fed into the mains. Unless the lamp is only for your own use and you're prepared to deal with the interference it generates.

There's a good design at http://www.epanorama.net/usercircuits/dimmer1/ that shows how the interference filtering should be done.

C1 and L1 are the interference filter components, and R4 and C4 are a good idea as well, although C4 is specified at 38 nF which is a very unusual value, so you can use another 22 nF capacitor like C1 for that position.

C1 and C4 should be "X2 rated" - designed for permanent connection across the mains. For example: http://www.digikey.com/product-detail/en/R463F222000N0M/399-5922-ND/2571356

The inductor (L1) can be http://www.digikey.com/product-detail/en/5248-RC/M8270-ND/774810 (this one is 68 µH; the value is not critical).

 

[hellraizor]

I didn't plan to dismantle the board I bought. I just bought it so I could basically copy how it was put together. Since I have no previous experience working with a pcb before I thought it would be a good idea to see what was connected to what. What kind of issues would interference cause?

 

[(*steve*)]

I didn't plan to dismantle the board I bought. I just bought it so I could basically copy how it was put together.

If the board will fit, dismantling it is not such a bad idea. But obviously there is nothing preventing you from having a go yourself.

Since I have no previous experience working with a pcb before I thought it would be a good idea to see what was connected to what.

Good point. However remember that similar components (especially those with three legs) may have their leads in a different configuration, so you can't expect to be able to wire it up just as you see -- you need to check first.

What kind of issues would interference cause?

Snow on analog TV, total disruption of digital TV, noise on your radio and other audio equipment, etc. You may not get all of these (you may not get any), but then again, your neighbour might.

Another thing is that the mains is a very high energy source of power. Expect that if you wire anything incorrectly you are risking things burning out or even exploding, and certainly you risk fuses blowing or circuit breakers tripping.

Personally, you are also risking death. It sounds melodramatic, but mains can kill. This is at least partly why I have stressed that the entire device needs to be earthed as that will help protect others in the case of a fault developing after you have constructed the lamp.

 

[hellraizor]

I hope to follow the schematic that I had posted. I purchased the already put together dimmer board so that I can see what is connected to what because visually the schematic doesn't help me as much as it may help other people (I am completely new to this and am trying to be as safe as possible). I will take care of the interference issue by following the advice given here as well as the safety advice working with main power. I'm sure I will have a million and one more questions once I start putting this thing together.

 

[hellraizor]

Ok so im wondering about the triac. I'm looking to buy some BT136 triacs. They are 600v 4A triacs. I looked up the specs and the pins are designated main terminal 1, main terminal 2, and gate. What pin goes to what? (Based on the schematic from here) http://www.aaroncake.net/circuits/dimmer.asp Thanks guys. Sorry I'm such a noob.

 

[(*steve*)]

If you look for a BT136 datasheet (Just google for BT136 datasheet") then you'll find a document which describes all you need to know.

To save you the effort, here is one I prepared earlier

You'll find drawings of the physical device, the schematic symbol, each with labelled pins. If you compare the schematic symbol in the datasheet to the schematic diagram, you'll see how it almost exactly corresponds (it may be rotated, mirrored, or have some minor variations). From that you can match the schematic to the pins you need to connect.

 

[hellraizor]

Thank you. So by going off the diagrams and matching the symbol up. It looks to me that the gate goes to the bottom of the schematic to where the AC comes in, T2 goes after the potentiometer and before the light bulb, and T1 goes to the diac (I'm using a diac instead of the neon lamp). If you have the time would you mind verifying?

 

[hellraizor]

Ok so after looking at the schematics and such I drew up this horrible visual as I understand how things should connect. How does it look?

 

[hellraizor]

Oh there should be a connection of the resistor where the line connects to the line between the cap and potentiometer. I forgot to put the black dot there.

 

[KrisBlueNZ]

That drawing looks good except that the diac connects to the gate. That is the wire that enters at an angle in the schematic symbol. It's pin 3 according to the data sheet. (The data sheet shows the symbol rotated anticlockwise from the normal orientation. Bad Philips Semiconductor!)

MT1 (Main Terminal 1) on pin 1 connects to the wire that runs along the bottom of the drawing. MT2 connects to the output terminal and the potentiometer.

So you just have pins 1 and 3 exchanged.

 

[hellraizor]

Ok thanks. For a second there I almost thought I had it figured out haha. Easy fix though. I'm glad I didn't hack it all to death. Thank god for this forum otherwise I'd probably end up burning my house down.

 

[hellraizor]

Here's another question. The schematics call for a 2 .068 250v capacitors. Im looking on ebay for these and I'm not really seeing many that look like the one I saw in the video of the completed dimmer that the schematic is based off of. Do I have some moving room with either of the numbers of the capacitor or does it have to be those exact specs? Looking on ebay for them using .068 capacitor as my search term I find all kinds from 50v up to like 600v. What number is most important, the .068 or the 250v?