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Author Topic: First steps: what exactly do I need for this project? and where do I get it?  (Read 391 times)
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Detroit
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Hello All,
  I am new to the forum, and this is my first post.  As far as introductions go, I am a product design student living in the states.  My electrical experience is limited to re-capping vintage amplifiers and building a few guitar pedals (from kits), however Arduino is completely new to me.

*I hope that I am posting this in the correct forum, if not, please advise.

Anyway, I am currently working on a lamp project which requires a custom dimming circuit, and I've been told that Arduino may be the best route.   

First off, imagine a standard wall-dimmer/switch that is controlled by a rotary knob.  When turning the knob clockwise, the lamp gradually becomes more and more brighter until the internal potentiometer has been 'maxed out' and can no longer rotate.

I however, want to the ability to continually rotate the dimming knob 360degrees without any stops.  And depending on where the knob is positioned, the lamp will be either: off, dim, or bright.   I understand that continuously rotating potentiometers already exist, however, I am restricted to the standard linear 'sweep' pattern which goes from 'off' to 'full brightness' in a 300degree rotation (before hitting a stop).

So lets hypothetically say that in this new Arduino driven circuit, the lamp will go from 'off' to 'dim' to 'bright' to 'dim' and the back to 'off'.  In one single 360 turn of the knob.  Does that make sense?

I spoke with a friend who knows a little about this stuff and he mentioned that I would the following:  Optical Encoder (with analog output), Arduino Unit, and a Light Control Module (which is controlled by 5 volts).

I have no idea as to what type of components to get, and I also don't know how to program the Arduino as well.  And to make things difficult, I would like to make two versions;  one for a 120V Incandescent light circuit, and another one for a 12V LED circuit.

Also, I am also willing to pay someone for the programming aspect.

Please advise.  Many thanks!

tachyhon@hotmail.com
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Switzerland
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For the rotational device a mechanical rotary encoder will do the job well enough and is quite cheap (p.e. http://shop.boxtec.ch/rotary-encoder-illuminated-p-40409.html). They rotate 360° and depending on the programming you can apply any pattern to it.

The light control module is a bit more complex. Dimming modules are different depending on the load they have to control. The circuit to control inductive loads (many halogen lamps are 12V and use a transformer to get that voltage) is different from an Ohm resistive load (classical bulbs) which is different from neon tubes. What type of load do you wanna control?

The circuit for a 12V load is relatively easy. A power MOSFET should do the bulk of the job.
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The actual lamp dimming functionality is actually usually some kind of triac or scr,   controlled
by the potentiometer.

In principle you can regulate the lamp with the potentiometer alone,  but it wastes a lot of
energy and you have the problem of waste heat dissipation from the device itself.
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Detroit
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The light control module is a bit more complex. Dimming modules are different depending on the load they have to control. The circuit to control inductive loads (many halogen lamps are 12V and use a transformer to get that voltage) is different from an Ohm resistive load (classical bulbs) which is different from neon tubes. What type of load do you wanna control?

The circuit for a 12V load is relatively easy. A power MOSFET should do the bulk of the job.

Well, I was hoping to use a standard 75watt incandescent bulb at 120v.  From my research, it has a load of 192ohms.  Does that help narrow it down?

What is a 'power mosfet'? any suggestions on what one will work? and where can I find one?  Im telling you, I really am new to this!  Thanks!
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Detroit
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The actual lamp dimming functionality is actually usually some kind of triac or scr,   controlled
by the potentiometer.

In principle you can regulate the lamp with the potentiometer alone,  but it wastes a lot of
energy and you have the problem of waste heat dissipation from the device itself.

Yes, I've come across what I now know as a Triac while opening up a few dimmer switches.  My initial intent with this project was to get a custom potentiometer made with the custom 'sweep' that I needed and swap it out with the stock one from the dimmer, but I've been running into brick wall after brick wall with that search.  I was once quoted $15,000 to have one made.  No thanks.

Any other suggestions?
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Croatia
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If you have an old mouse (one of those things with a ball) open it up. The ball sits on two perpendicular shafts, each connected to a slotted disk. These disks rotate in front of the optical sensors which determine the direction and speed of rotation. Looking at that mechanism might give you some insight to what you need.
It is called rotary encoder and there are two different kinds. One detects direction and speed of rotation. The other one detects the angular position. Either one can be adapted to your needs, but the angular one would be somewhat easier to code.
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Quote
What is a 'power mosfet'?

http://en.wikipedia.org/wiki/Power_MOSFET

This might be a good candidate, has a max. current of 49A, if that's enough for you.
http://shop.boxtec.ch/mosfet-irfz44n-p-40639.html

To control your bulb you can use a triac (two thyristors) and a phase control circuit:

http://commons.wikimedia.org/wiki/File:Phase_control_schematics.svg

and

http://en.wikipedia.org/wiki/Phase_fired_controllers

The control circuit for the triac is usually a IC today: http://www.infineon.com/dgdl/tca785_green_050217.pdf?folderId=db3a304412b407950112b437a09d6866&fileId=db3a304412b407950112b437a1216867
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