Flashing LED lights on Christmas tree

Thread Starter

Martin Cox

Joined Dec 11, 2017
4
We have just bought a Christmas tree with some LED lights on it.
I would like the LED's to either flash or ideally fade on and off.
I need some help please to spec some components to make this happen.
I assume that I will need to give the power supply voltage and the current drawn to do this?
Thanks.
 

Dodgydave

Joined Jun 22, 2012
9,643
We need to know what voltage the leds are, ideally post a picture of the led psu...

For flashing lights a 555 timer is ideal, for fading up/dn pwm is used.


wnpGx.png
 
Last edited:

Ford Prefect

Joined Jun 14, 2010
201
It's most probably a 12v DC supply..but, it maybe better to use opamp(s) with a combination of resistors and capacitors connected up as an oscillator to fade the LED's on and off.
 

Reloadron

Joined Jan 15, 2015
5,667
I assume that I will need to give the power supply voltage and the current drawn to do this?
As mentioned that would be a yes. Once what you have is known in some detail then methods can be suggested for various lighting effects. There are several ways to achieve effects which can be discussed once more is known as to whet you have.

Ron
 

Thread Starter

Martin Cox

Joined Dec 11, 2017
4
Thanks,
The power supply is outputting 3V DC at 500mA to the LED's
As best as I can count there are 35 LED's on the tree.
 

Dodgydave

Joined Jun 22, 2012
9,643
So all the leds are in parallel with a series resistor for each led,probably 100 ohms,.
The circuit in #post 2 would work.

Make the transistor a Tip41c
 
Last edited:

Audioguru

Joined Dec 20, 2007
11,249
Of course all 35 LEDs are connected in parallel like my cheap Chinese flashlight with only the wall wart limiting the current.
A little BC547 transistor will smoke and burn when trying to switch 500mA (its max allowed current is only 100mA).
On the other website a nice little 2A Mosfet was recommended with a gate that works down to 1.2V.
A Cmos 555 is guaranteed to work with a supply as low as 1.5V.
 

Thread Starter

Martin Cox

Joined Dec 11, 2017
4
Of course all 35 LEDs are connected in parallel like my cheap Chinese flashlight with only the wall wart limiting the current.
A little BC547 transistor will smoke and burn when trying to switch 500mA (its max allowed current is only 100mA).
On the other website a nice little 2A Mosfet was recommended with a gate that works down to 1.2V.
A Cmos 555 is guaranteed to work with a supply as low as 1.5V.
The other website?
 
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