K8064 control voltage


#1

Hello,

I have the module “K8064” and actually it works, but can I adjust the control voltage by e.g. changing some resistors, to 0-4.7V instead of 0-5V?

The module is designed in original for a control voltage of 0-5 V (max.
0-12V).
Because my available control voltage is not quite 5V, rather only max.
4.7V,
it is not possible for me to bring the output power to 100% with that voltage.
Even if RV2 is fully turned counterclockwise, the green LED is not glowing constantly, it still only flashes.


#2

You can adjust the control voltage with the 2 trimpotentiometers, normally 4,7V can’t be the problem.
Even with 5V, the max brightness is max 98%.


#3

4.7V is the problem! The green LED will stop flashing only at min. 5.31V.
With the 2 trimpotentiometers it is not possible to adjust the brightness to the max. of 98% with 4.7V.


#4

the problem could be after the optocoupler. First you must be sure of the power supply on the PIC controller.
You can measure this between pin 1 & 14. (must be around 5V).
ATTENTION: Every part is under high voltage !!!
Normally, analog IN on the PIC is max 4,85V.
You can boost this by removing R19 and replaced this with a ‘jumpwire’.


#5

[quote]…First you must be sure of the power supply on the PIC controller.
You can measure this between pin 1 & 14. (must be around 5V).[/quote] Yes, the voltage between pin 1 & 14 is 5V.

Now I have found out that the real problem is the too small dynamic range, which results from the control voltage of 0-4,7V at Pin 9 (PIC).

To switch the lamp to 0%, the voltage at Pin 9 must be less than 2,46V.
To turn it on 98%, the voltage at Pin 9 must be min. 4,32V.
This results in a required minimum range at Pin 9 of 2,46-4,32V (difference: 1,86V).

With a control voltage of 0-4,7V this area is not completely covered.
The range that results from this control voltage is, depending on the potentiometer settings, 2,89-4,32V or 2,46-3,91V (difference: only 1,43V !!!)
Therefore the brightness can not be controlled over the full range!

Now the question is, how can I achieve the minimum range at pin 9 with the control voltage of 0-4,7V?
I think the combination of the resistors R18 and R19 must be another. But I am not sure.
Or maybe other values for R11 and R12??


#6

Ok, I have solved the problem.
I replaced R16 (4,7K) with 3,6K and now it works as it should.


#7

Happy to read you have found a solution!


#8

Hello,

I have a very similar problem, but I need to control it with a maximum of 3.3V, as opposed to Mark’s 4.7V. Could anyone please recommend a resistor to use in place of R16? Thank you.