Hello,
is it only possible to use red LED’s with this module or is it also possible to use ie. blue LED’s? I can’t seem to find if there 's a resitor in line with the LED or already at the print. In the last case I asume there’s only the possibillity to use all other LED colors exept the blue and wihte ones.
Resistor is internal. Low current blue and white leds should work fine. Give it a try.
is it possible to receive a copy of the schematic of the vmb8pb or at least the part of the pic driving the led’s (resistor setup). I want to make a small driver print to drive blue/red duoled’s. Since I only can find 3 pin duoled’s of that kind and normal versions (20mA), the emmission is to low to put them behind a switch (in my case bticino living series).
An easy solution without tampering the VMB8PB itself:
Use opto’s to drive other stuff (LED’s, …)
The following version works just fine, but i’m experimenting with other opto’s (with darlington output/higher CTR to get rid of the switching transistors)
The VMB8PB has a constant current output of approx. 2mA to drive the low current LED’s (for different intensities the duty cycle changes)
In this application the VMB8PB outputs drive the LED’s inside the optocoupler (K847P, has 4 separate couplers in one IC so 2 are needed to cover the 8 VMB8PB outputs), the optocoupler output transistors drive BC547B transistors which control the LED’s you want to use
As the CTR (current transfer ratio) of the used opto is too low to directly drive standard LED’s, therefor a GP transistor (BC547B) is used to switch the LED’s (I used the Velleman R2000B switches with blue LED ring > internal resistor, works directly on 12Vdc)
The power is taken from the present 12Vdc Velbus supply
Connect the numbered VMB8PB output with one side of the switch and with the optocoupler input LED cathode
Connect the VMB8PB Com with the other side of the switch and with the optocoupler input LED anode
Connect the optocoupler output collector through a 6.2k ohm series resistor to the +12V supply
Connect the optocoupler output emitter with the BC547B Base
Connect the BC547B emitter with the - of the supply
Connect the BC547B collector with the cathode of the LED you want to use
Connect the anode of the LED through a 680 ohm series resistor also to the +12V supply
K847P datasheet is found here:
pdf1.alldatasheet.com/datasheet- … 847PH.html
Idd, but I kept that solution as last one. As far as I can see, this is going to be the easiest way. Just have to see that ther’s place enough behind the switches, problably a smd pcb or something.
Swopped the K847P opto’s yesterday with KB815 photocouplers with a very high CTR (min. 600% @ If=1mA)
As expected this works flawlessly - up until this morning that is 
Using this photocoupler you don’t need any external components to drive other LED’s
You need 12V power supply for the VMB8PB anyway, so the easiest solution is to use this to drive the LEDs with a 620ohm series resistor
The package is a very small 4pin DIP which will fit almost anywhere.
My next step is to design a small PCB which fits directly onto the R2000B
data sheet here:
kingbright.com/manager/upload/pdf/KB815(Ver1189489821.9)