led pulse / breathe light board

[davit]

hi
i have this little 8 led breathe light circuit
which are wired in series 2 at time
i need to slow down the pulse
it came with a 20k pot / trimmer
i tried a 5k and 10k with no differance
do i need a higher vaue, looking for about 3 second
pulse, can anyone sugest a size to use
many thanks
davit

 

[AnalogKid]

Schematic?

The photo is so fuzzy it contains very little information:

What are *all* of the markings on the chip?
Can you post a more clear photo?
Can you post a clear photo of the bottom side of the board?

You said you want a 3 second pulse, but you didn't say what the pulse time is now - ?

Can you post a link to where you got the board?

ak

 

[davit]

thanks for the reply,
wil borrow a camera off someone
meanwhile found this info
( pulsing 1 second at present )

Can change LED flash Frequency by adjusting Potentiometer
Supply voltage: 11-13V, recommend 12V
The main control chip: LM358
Light Color: bright blue
LED quantity: 8 LED
Dimension (L x W ): Approx.4.2 x 2.9cm /1.65" x 1.14"

 

[AnalogKid]

The LM358 is a dual opamp, almost certainly configured as a comparator with hysteresis to form a square wave oscillator. Depending on the exact circuit, it is entirely possible that changing the value of the pot has no effect on the adjustment range. In this case, some other resistor on the board sets the range, and the pot sets a percentage within the range.

ak