Fade each color of RGB LED's with 555 / 4029

[ThomsCircuit]

If you can use non-common anode/cathode LED's

I found these.
Says its a5050 3watt 20ma each color. ill try to find a datasheet

 

[ThomsCircuit]

Definitely stick with a separate 12V supply; Six 1.5V batteries would start at around 9V, but steadily drop down to roughly 6V over their lifetime, causing the LEDs to progressively dim.
This chart is for a typical AA cell, triple A would have a rather shorter life at a given load..

Thank you. ive been wanting to know this. Awesome!

 

[ThomsCircuit]

ill try to find a datasheet

RGB 6pin datasheet

 

[ThomsCircuit]

So each group of three LEDs would consume only 20mA and require 1 current limit resistor. You might even be able to go back to using the 2N3907, depends on the gain of the transistor.

Oh im totally liking this. The 3907 that is. much smaller. ive got limited room. Im going to lookup how id connect these in a series.

 

[ThomsCircuit]

LEDS in a series.
So my voltage will be 12volts. Confirmed.
3.0fv led 150r
2.0fv led 350r

 

[eTech]

LEDS in a series.
So my voltage will be 12volts. Confirmed.
3.0fv led 150r
2.0fv led 350r
View attachment 135827

Are you not going to use 8 Leds for each?
You can put the last two of each in their own group with their own resistor.

Also be aware the TIP122 has a lot of gain, so with it you can use a larger value base resistor, which should make the capacitor size smaller. You should test these different configurations before settling on specific values.

 

[ThomsCircuit]

You can put the last two of each in their own group with their own resistor.

yes. i was drawing up a quick example.
the resistors for the last 2 pairs of 2 leds each will be 430 and 300r

 

[ThomsCircuit]

Are you not going to use 8 Leds for each?

LMK if this allows the use of the smaller 3907 transistors

 

[Pommie]

I'll keep quiet.

Mike.

 

[eTech]

LMK if this allows the use of the smaller 3907 transistors

The only thing I can tell you is that the TIP122 will deliver 20mA to each led without making the base resistor so small (and the cap so large) that you loose the fade on/off effect. You'll have to experiment with what works for you.

 

[eTech]

I'll keep quiet.

Mike.

No need to keep quiet.

 

[ThomsCircuit]

I'll keep quiet.

you have been awesome! Ive even put your name on the PCB.

 

[ThomsCircuit]

You'll have to experiment with what works for you.

THE BIGGEST ISSUE WILL BE MOUNTING THE LEDS. THEY FLOAT ABOVE THE BOARD

 

[ChrisP58]

You might look at using mosfets instead of the 2N3907s. The gate (the base pin of a mosfet) current is effectively zero, so you could increase the timing resistor to 100K (or higher,) with a similarly reduced capacitance.

 

[ChrisP58]

THE BIGGEST ISSUE WILL BE MOUNTING THE LEDS. THEY FLOAT ABOVE THE BOARD

I assume that what you mean is that you want the position of the light source to be above the PCB surface.

The standard way of doing that is with a light pipe. A small plastic rod that carries the light to a different place. There are many sorts available.

 

[ThomsCircuit]

You might look at using mosfets instead of the 2N3907

We have calculated the TIP122 would be a good fit.

 

[Pommie]

Did you check the size of 1500uF 10V capacitors? 10mm dia by 12mm long. Instead you've gone with 470uF caps - 10mmx10mm a huge saving of a whole 2mm.

Mike.

 

[Pommie]

We have calculated

No one seems to have calculated anything.

Mike.

 

[ThomsCircuit]

The standard way of doing that is with a light pipe. A small plastic rod that carries the light to a different place. There are many sorts available.

Cool. Thank you. i found a 6mm flexible version. should work out fine

 

[ThomsCircuit]

Instead you've gone with 470uF caps - 10mmx10mm a huge saving of a whole 2mm.

i thought they were 270. hmmmm