Random resonse from VMB4DC and VMB4RYNO

I have now set up Velbus in several rooms of house and works pretty much exactly as I expected. The only probelm I seem to be getting at the moment is a random switching of my VMB4DC, which controls a 0-10v LED dimmer and a VMB4RYNO, which controls non-dimmable lights. Both of these are switched by a VMB6IN, mounted remotely and a VMB8PB, mounted behind a light switch. These have been set up to produce mood lighting by dimming lights at various levels. The problem seems to happen completely at random when switching from 1 mood to another. Sometimes the lights will dim to the required level. Other times, the lights do not respond or stay at the previous mood level.

I am convinced it’s to do with contact bounce at the switches, but I have tried setting the closed delay on both the remote switch units from 65ms, 1s, 2s and the 3s level, and although the 1s does seem to be better, it does not iliminate the problem.

As anyone else encountered this problem and found a cure. Although I can live with it, it is annoying.


have you mounted feedback leds behind your VMB8PB?

If they act weird, they can cause a random control.

No, I havent used any feedback LED’s. Would using them help, or do you mean using them can cause random response?

I never mentioned that the VMB8PB is connected to a Velleman K6714 universal relay that is in turn connected to a K8046 touch panel. The VMB8PB is mounted close to the relays and the wires have not been extended.

I don’t think this is the problem though, because the dimmers that are also controlled on the mood selection too, works perfectly every time. It is only the VMB4RYNO and 0-10v dimmer that I have the random problems with.

Do the VMB4RYNO and 0-10v have problems with a maintained contact, as opposed to momentary? At the moment the Velleman touch panel is set up with maintained contacts.


we have no problems at all concerning the VMB4RYNO or VMB4DC. Since these modules only react to the presence of a configured push button on the bus, random action is just not possible.

Perhaps you have a cabling problem (responsable for 99% of malfunctions).
Did you use 2 terminators (1 central and 1 on the end of the longest distance)?
Did you consider the bus polarity?
Did you check all connections?
Did you configure using the auto detection (if a controlled relay is used as initiator too, you can end up in a loop).
Is your power supply high enough? (12V minimum)

In case of a problem, the bus will continue to work untill the error buffers are full. So it’s possible that sometimes the push of button does not appear on the bus, or it can appear later on, etc …