interactive rainbow led

[deemster2]

Hi,
I'm new here so don't be to hard on me.
I have a variable input low voltage and I would like to have a little buffer when the power is cut (like a few seconds). The buffer has to give the last given variable. It is for a rgb led, so I would like to keep the same color for a few seconds after the power is cut. Is there a way to do this?

Thank you so much
deemster2

 

[Arouse1973]

Hello deemster2 and welcome to EP.
Yes a capacitor could do this. What is the working voltage and current you require.
Thanks
Adam

 

[deemster2]

the rgb led need 3.3V and 20mA for blue and green, red needs 2.0V and 20mA.
A capacitor builds up a specific about of energy, can a it still give the variable signal?

 

[Arouse1973]

the rgb led need 3.3V and 20mA for blue and green, red needs 2.0V and 20mA.
A capacitor builds up a specific about of energy, can a it still give the variable signal?

What do you mean the last given variable?
Adam

 

[deemster2]

the rgb led changes its color. So the given V changes constantly.

 

[Gryd3]

Hi,
I'm new here so don't be to hard on me.
I have a variable input low voltage and I would like to have a little buffer when the power is cut (like a few seconds). The buffer has to give the last given variable. It is for a rgb led, so I would like to keep the same color for a few seconds after the power is cut. Is there a way to do this?

Thank you so much
deemster2

I would like to say this is not possible with a simple solution.. and here's why...
Putting a capacitor on each Red, Green and Blue line will certainly help keep that color lit for a variable time after power is removed... but the capacitor values need to be chosen carefully so that the 3 colors fade at the same time... If you decide to adjust the color of the strip, your capacitors will need to be readjusted or the color will change as it powers off.
The only solution I can think of is a large capacitor, or a small battery backup 'before' the LED driver... the one that is responsible for controlling the LEDs. Otherwise your LEDs may fade colors as it turns off.

 

[deemster2]

The last thing is not a option. I'm taking the led from the led controller...

This is the rgb variables the led gets. I'm wondering if by adding a capacitor the values will change to the output of the capacitor?
I don't have any at home zo I can't try it out...

 

[Gryd3]

The last thing is not a option. I'm taking the led from the led controller...

This is the rgb variables the led gets. I'm wondering if by adding a capacitor the values will change to the output of the capacitor?
I don't have any at home zo I can't try it out...

Here's the tricky part:
Say you want to output a very light lime-green.
This will be 100% green, say 75% red, and about 50% blue.
A capacitor is a very short term storage which looses energy very quickly. Each color will use power at a slightly different rate. This will require you to pick slightly different values, and/or add a resistor to help balance out the energy used by each color to ensure they all fade at the same rate.
If they do NOT fade at the same rate, then you will find your light lime-green will will darken, and turn more green or even red before turning off depending on which color draws more current.
This is not an ideal solution.
What are you trying to accomplish?

The only other option is a powered device like another microcontroller that reads the input from the LED controller and drives the LEDs itself.

 

[deemster2]

I'm trying to make a bottle that changes color like a rainbow and when you take it off the bottle should interact.
Don't really know how to do that yet. (BTW: the led is in the bottle and the bottle is not for decoration, there are several bottles, I want the bottles to connect with magnets on the bottle and stand).
I would be ideal to have the bottle stay the same color als it last was, but that seems impossible.
I thought it would be able to get the led a fixed color with capacitors after I take it of for a few seconds.
But that seems nearly impossible to so I think I will have to compromise XD
I'm thinking about a separate led in the bottle that will turn on when the bottle is taken of, but I don't know how to do that... I thought about a light sensor but I think that wont work...

 

[Gryd3]

I'm trying to make a bottle that changes color like a rainbow and when you take it off the bottle should interact.
Don't really know how to do that yet. (BTW: the led is in the bottle and the bottle is not for decoration, there are several bottles, I want the bottles to connect with magnets on the bottle and stand).
I would be ideal to have the bottle stay the same color als it last was, but that seems impossible.
I thought it would be able to get the led a fixed color with capacitors after I take it of for a few seconds.
But that seems nearly impossible to so I think I will have to compromise XD
I'm thinking about a separate led in the bottle that will turn on when the bottle is taken of, but I don't know how to do that... I thought about a light sensor but I think that wont work...

Perhaps you can make something work...
Use a different LED:
Many addressable LEDs have a built in microcontroller that keep the last value it was told while the LED is powered up. Some require frequent 'refreshes' to stay the same color, so you should look at the data sheet.
There is also http://thingm.com/products/blinkm/ or you can make your own with a small PIC or AVR microcontroller and a tiny bit of code. (Heck , if you do it this way, you could use a small rechargeable battery and they could stay lit much longer.)

 

[deemster2]

Oh wouw I didn't know that existed. How are these led with micro controlers thingies called? I tried to search it but couldn't find anything. The blinkm are very awsome thnk. For this project it is just to expensive because I'm busing serveral bottles.
Thank you very much. You've been a great help.

 

[Gryd3]

Oh wouw I didn't know that existed. How are these led with micro controlers thingies called? I tried to search it but couldn't find anything. The blinkm are very awsome thnk. For this project it is just to expensive because I'm busing serveral bottles.
Thank you very much. You've been a great help.

Simply do a search for 'addressable led'
You'll find plenty.

The trick here is that they will communicate differently... There is power, ground, and data.
The data line carries serial data to set the color of each LED. The trick you will want to be able to pull off, is having a contact for power, ground and data, and you need to make sure that the addressable LED you choose can still operate when no more data is sent.

 

[deemster2]

oke the addressable led need a different kind of input and such... It is a good idea but I already have the led I wanted to use, so if I want to use the addressable led I would have to practically start over again... Thnx anyway I'm most definitely gonna use it some other time.
About a separate led in the bottle which turnes on when the bottle is taken off how do you think is the best and easiest way to do that?
I thought about this:

but I don't know what to do to make the led be turned on when the bottle is off the stand and be turned on when the bottle is on the stand. It should work like a inverted switch or something.

 

[Gryd3]

oke the addressable led need a different kind of input and such... It is a good idea but I already have the led I wanted to use, so if I want to use the addressable led I would have to practically start over again... Thnx anyway I'm most definitely gonna use it some other time.
About a separate led in the bottle which turnes on when the bottle is taken off how do you think is the best and easiest way to do that?
I thought about this:

but I don't know what to do to make the led be turned on when the bottle is off the stand and be turned on when the bottle is on the stand. It should work like a inverted switch or something.

I'm not sure how you can do that with just an LED and capacitor. My first thought was a small reed switch. Would disconnect the LED while a magnet was present.