limit inrush current shutter

[TeTTiweTTi]

Hi,
I have a dozen Philio PAN8 in use to control my shutters.
In the last months 2 broke down. There were still communication in the network, but they were unable to switch anymore. I believe the power switching relay "sticks".
Does anyone has experience with this and is there some electronic component I can use to limit the inrush current of the shutter motor?

Thanks,
Steve

[joegr]

Yes, there are such devices. They are actually called in-rush current limiters. They are thermal resistors that have a relatively high resistance at room temperature. The current flowing through them heats them up and they go to a much lower resistance when hot. Here's a random example.
http://www.mouser.com/ProductDetail/...sQJGtlSozv8%3D

You need to know the normal (not starting) load current of your load, the load's resistance when no powered, the voltage, and the max current your relays can switch. Then you can pick some to try.

[ericg]

The post by joegr might fix your problem, but there's another possibility that also relates to relay failure.

I don't have any PAN8, but I do have a somewhat similar device, the Qubino Flush 1D relay. You and I have an application commonality in that we are both using a tiny Z-Wave relay to control an inductive (motor) circuit. I suspect it may be more likely that your relay sticky contacts may be failing from what happens when you open the contacts, rather than when you close them.

The current through an inductive load wants to keep flowing. When the relay contacts are opened, the result is a very high voltage that can cause arcing. The process is similar to the way an arc welder works. Enough of this arcing can cause the contacts to try to weld themselves together, creating the sticking effect.

For this type of problem, the recommended treatment is an RC circuit (resistor and capacitor - sorry, I don't know your background) called a snubber. Fortunately, Qubino recommended that I use one if I planned to control a motor. You can read about it in their user manual, page 52. The reference also shows how to add the snubber to your circuit. (Google "qubino flush 1d relay user manual" without the quotes.)

I used the snubber they recommended, and have had no problems, so far. I got mine from Allied in the US for about $2.00 each. Since you are in Belgium, you might find a better source.

I hope this helps.

[joegr]

I do agree that the snubber is the more likely fix.

[TeTTiweTTi]

Hi guys, both thanks for the quick and comprehensive reply. just a pity there are 2 conflicting solutions :-)

the 'snubber' is quite convincing as it is explicitly mentioned in the manual of a similar qubino device.
to what I find the 'in-rush current limiters' is typically used to limit the current when a circuit board is powered on.

I will try do do a test one I have a spare roller motor.


btw: I 'repaired' the relay by giving it a good hit, which made the sticking contacts come loose. It's a general tip I found online.

[drhtmal]

btw: I 'repaired' the relay by giving it a good hit, which made the sticking contacts come loose. It's a general tip I found online.

Good ol' percussive maintenance. Does the trick all the time.