New Light (help with circuit design)

[slayershunt]

Hey just looking for a little help with a project i'm working on. I'm looking to obtain a lamp which can change light between a huge number of colours. Similar to the Philips Living Colour Lamp. However looking at the price tag (a hefty £90) i began to look into building one myself. In terms of the electrical components they can all be obtained for under £15. And the perspex framework can be obtained for another £7.

 

The flaw in the plan is the circuit diagram, as the only way i can see to make it work is to use a custom made variable resistor to change between the three colours. Any help with replacing this with an easier or cheaper component would be much appreciated. (IMPORTANT NOTE: the component must switch between the LED's in an analogue fashion so all possible permutations of the three LED's can be used and moved between using just ONE switch/knob/dial)

 

Any thoughts on the design, possible circuit flaws and general scope of the project would be much appreciated.

 

Heres a few very very very basic diagrams to explain just what i'm talking about.

 

The Circuit Diagram

 

 

The Custom Variable Resistor

 

The Basic Design

 

 

(Controls would be external)

 

 

 

 

The concept seems like a good idea as the lamp will use very little electricity, will look stylish, will be unique and will likely never need replacing (LED's last around 50000 hours (about 13 years at 10 hours of useage a day)

 

If this is successful then i may expand the project to allow linear arrays of the tubes which can be added and removed at will with the circuit reconfiguring itself to stop short circuiting. (by means of a rather clever switch i have designed)

[gonpost]

Hey,

 

The variable resistor thing is kind of silly. Why not just have a plain resistor before each LED?

 

As for switching, I'm not sure. I'd just leave the three wires out and connect them as I pleased. :D Maybe put them in a mini breadboard.

[slayershunt]

Hey,

 

The variable resistor thing is kind of silly. Why not just have a plain resistor before each LED?

 

As for switching, I'm not sure. I'd just leave the three wires out and connect them as I pleased. :D Maybe put them in a mini breadboard.

 

The variable resistor is what allows the light to change to the various colours. i,e red and green will produce a yellow light. While i could place a variable resistor before each of them it would mean having to adjust three switches to control the colour, and also would mean one LED could be overloaded by turning the other two off entirely.

[Sbrideau]

How did my post end up here?

[JoeDaStudd]

You can buy tri/multi colour LED's which cost less then £1 and allow you to create any colour with a single LED.

 

I'm kinda lost on how it totals to £15 on components.

£4 mains to 9v converter

£1 variable resistors

£2 switch

 

Which leaves £8 for you your LED's and custom variable resistor.

 

I would definitely take out the array of LED's and custom variable resistor, replacing it with a multicolour LED and standard variable resistor.

[gonpost]

Hey,

 

The variable resistor thing is kind of silly. Why not just have a plain resistor before each LED?

 

As for switching, I'm not sure. I'd just leave the three wires out and connect them as I pleased. :D Maybe put them in a mini breadboard.

 

The variable resistor is what allows the light to change to the various colours. i,e red and green will produce a yellow light. While i could place a variable resistor before each of them it would mean having to adjust three switches to control the colour, and also would mean one LED could be overloaded by turning the other two off entirely.

 

Hmm...see, I guess I don't understand. From your picture, it looks like you just have 3 LEDs there. Are there actually more? If you explain very well I might be able to help better.

 

Because as I see it now, those are really just three LEDs in parallel, and it doesn't matter how many you have connected in parallel as long as your voltage source can supply enough current (I'm assuming you're using the wall, so I'd assume that's not a problem).

[slayershunt]

You can buy tri/multi colour LED's which cost less then £1 and allow you to create any colour with a single LED.

 

I'm kinda lost on how it totals to £15 on components.

£4 mains to 9v converter

£1 variable resistors

£2 switch

 

Which leaves £8 for you your LED's and custom variable resistor.

 

I would definitely take out the array of LED's and custom variable resistor, replacing it with a multicolour LED and standard variable resistor.

 

Thats a seriously good call on the tri-colour LED's didnt actually know they existed, however after looking into them the custom resistor would still be needed due to the way they are wired in. (In effect the circuit diagram is exactly the same just all three LED's are effectively contained in one bulb). On the upside though it will reduce the number of LED's by 2/3s so thanks very much.

 

After playing about with a few pieces of graphite and zinc i have actually managed to make my custom resistor. It's a tad bulky at the moment (about the size of a small apple) but i'm pretty sure it can be made smaller with relative ease.

 

I've ordered my perspex tubing, and the various components needed to actually build the light. Hoping to have a rough prototype in about 2 weeks. For now i'm just going to work on miniaturizing the variable resistor and building a small control box to house all the controls.

 

Also had a play with the switch design i mentioned at the end of my previous post and it seems to be working so far. It should mean that i can link up several of the tubes but only need one control panel and also not suffer any loss in power to the LED's as the circuit will automatically compensate for the new components added.

 

 

Thanks very much for all the help given so far