Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?

The box is branded Nico IIRC.

Thanks,
Stephen.

"Stephen" wrote in message
...
Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?


If relay is hard wired then replace with a Maplins equivalent or
alternatively hard wire from the terminals a replacement

HI Stephen

Stephen wrote:
Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Was the controller new (or sold as 'new').?
Maybe the dodgy relay is why it was on ebay ?


Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor?

Probably

Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary?

Very likely

If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

If all that your switch is doing is to short out the relay contacts then
it shouldn't do any harm.... but do you know how the power to the motor
is cut when the door is at 'full open' or 'full shut'. If this is done
by the control box then adding a manual control across the relay could
be very dangerous...


I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?

You're confusing two things here, I think.
The reverse emf from the relay coil (assuming that the relay coil is fed
from a low DC voltage) will appear on the low-voltage side of things -
and should be absorbed by a diode connected across the coil.

If you're seeing sparks then they are coming from the contacts
themselves - which are on the mains side of the relay. Don't fit diodes
to these contacts - they won't last very long..... There might be some
point in fitting a high-voltage capacitor across the relay contacts....
but make sure it's one that's rated for mains use.

Have you mentioned it to the seller - might be a plan before trying to
re-engineer it yourself....

Regards
Adrian

On Thu, 20 Nov 2008 20:48:57 +0000, Stephen wrote:

I have opened the box of electronics and given the relay a tap and it is
working for now but I expect it to stick again soon.

It may never stick again... but see below.

How can I prevent it from sticking in the future?

Replace it.
I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate.

The contacts will be switching the motor current not the coil. Diodes
won't be much good on mains you need to fit a mains rated "snubber"
circuit across the contacts that are arcing. Something like:

http://cpc.farnell.com/FT00711

Possibly this is welding the relay stuck.

Quite likely so the simple tap above may not be a cure all.

I detect some rather basic questions, are you sure you are up to delving
into this box with live mains?

--
Cheers
Dave.

In message , Stephen
writes
Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future?

Angle grinder

Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

No - I think you should stay away from things you don't understand

There is no such thing as a "sticky" relay, what do you think "sticks"
??

So, you tap it and it works ?

sounds like the coil voltage is borderline, or you have a cracked joint
or something

Don't just replace the relay, I doubt it will have any effect


Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?

yeah - pour a couple of dozen on top, see what happens

Honestly, I think you should let someone with a clue have a look at it,
it doesn't sound like something you should be diving in to, you are
likely to do more harm than good


The box is branded Nico IIRC.

Thanks,
Stephen.

--
geoff

Stephen pretended :

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Tapping it might free welded contacts, but not usually make open
contacts close. That sounds more likely a poor soldered joint on the
PCB.


Does anyone know the schematic for these boxes of tricks?

You could ask the manufacturer if he might supply one, but you may need
to convince them that you know what you are doing.

I presume the relays isolate the electronics from the motor?

Yes.

24v DC is a supply often used on the electronics/control side of the
door. Sometimes the motors are also 24v DC, but more usual is 240v AC
mains. The relay will probably be there to isolate one, form the other.


Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary?

Normally, yes.

If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

Probably you could, but not for certain without investigating the
circuit. If the relay has two connections for the coil, plus two or
maybe three for the contacts - and ONLY TWO contacts are used - then
probably it will be safe to wire a switch across it. If there are three
and all three are used then it definitely is not safe to do - it might
indicate some sort of braking on the motor.


My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?

The welding takes place as the contacts make. The contacts can spark on
both opening and closing, that is perfectly normal.

Reverse EMF and the use of diodes relates to the coil side of the
relay, not the switching contacts. If the controller is designed for
the door, then the sparking can be disregarded.

If you are certain it is the relay to blame, then fit a replacement.
They are not expensive, a pound or two each. Maplins might well have
them in stock, or Farnell, or RS. Usually there will be a maker/model
details stamped on the cases, type those into a search engine.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Stephen wrote:
Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?


Not if switching mains.

Can use a high voltage capacitor - 400v 0.01uf or so in series with a
resistor..

If relay easy to replace, replace with better.

If it can be opened, file contacts smooth for another year of life..well
it worked in my old XJS anyway ;-)




The box is branded Nico IIRC.

Thanks,
Stephen.

Stephen wrote:

Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Sticking is localised welding of contacts, caused by the contact
surface being rough and oxidised, which is normal wear & tear of
relays.

take the cover off the relay, use a little piece of medium-fine
sandpaper to smooth the contacts.


Does anyone know the schematic for these boxes of tricks?

Dont think theyre standardised.

I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other?

usually yes

Is the relay output open circuit when he door is stationary?

you tell me. Probably, but really you shouldnt need to ask that

If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

cant you figure out how to answer that? We cant see the circuit
working.


My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate.

the latter

Possibly this is welding the relay stuck.

yep

Do you think I should add diodes?

no, that only works for dc loads.


The box is branded Nico IIRC.

Thanks,
Stephen.


NT

"Stephen" wrote in message
...

Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

maybe, probably, maybe not, who knows,

your emergancy over ride should be the chain dangeling from the door, you
usually have to yank it hard in one direction, or wind it one direction or
something like that to get it to pop off the holder and onto the manual
operate pulley, then wind the door open or closed with it and fix the
controller/replace the motor when you get time.

"Stephen" wrote in message
...
Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.


Now that you have freed it off, it may not ever stick again. If it had been
a small carbon build up over the contacts, the slap you gave it might have
been enough to clean it. Daily operation might be enough to keep it clean.
But you'd have to tell us what the contacts on the relay look like. Are
they blackened and damaged? Looking inside the relay, does it look like it
really needs replaced?



Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?


What voltage doe the door run on? Have you connected to mains voltage
(240Vac)? What voltage does it say on the side of the relay covers or other
components? Did you get a transformer with the door, or did you have to
supply one yourself?

A separate switch as an override for what? Why don't you remove the
electronic controller and install two switches? One for open and one for
close.



My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!


If this is a mains voltage (240Vac) system, I don't think any part of the
control system will deliberately connect to an safety earth bond. That
would be really silly.



I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?


A relay will arc a little as the contacts make and break. It is why the
relay may have stuck in the first place, because the arc can cause a carbon
deposit to build on the face of the studs.

The controller most likely contains diode protection against field collapse,
so it shouldn't need any more. Definitely not across the mains contacts.



The box is branded Nico IIRC.

Thanks,
Stephen.


Best to find out who made the controller and search their website for a
manual on it. It should give you a better idea of what it can and can't do.

Good luck with it.

In article ,
Stephen wrote:
The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

It could be sticking due to a mechanical problem in which case simple
replacement should sort it. RS Components etc should do a suitable
replacement.

It might be sticking due to the contacts arcing and welding themselves
together - in which case the cause of this overload needs to be rectified.
There's usually some form of snubber network to prevent arcing when the
contacts open on an inductive load like a motor.

--
*Procrastinate now

Dave Plowman London SW
To e-mail, change noise into sound.

wrote:
Stephen wrote:

Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future? Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

Sticking is localised welding of contacts, caused by the contact
surface being rough and oxidised, which is normal wear & tear of
relays.

take the cover off the relay, use a little piece of medium-fine
sandpaper to smooth the contacts.


Does anyone know the schematic for these boxes of tricks?

Dont think theyre standardised.

I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other?

usually yes

Is the relay output open circuit when he door is stationary?

you tell me. Probably, but really you shouldnt need to ask that

If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

cant you figure out how to answer that? We cant see the circuit
working.


My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate.

the latter

Possibly this is welding the relay stuck.

yep

Do you think I should add diodes?

no, that only works for dc loads.


The box is branded Nico IIRC.

Thanks,
Stephen.


NT

http://www.wiki.diyfaq.org.uk/index.php?title=Snubber

On Thu, 20 Nov 2008 21:20:55 +0000, Adrian
wrote:

If all that your switch is doing is to short out the relay contacts then
it shouldn't do any harm.... but do you know how the power to the motor
is cut when the door is at 'full open' or 'full shut'. If this is done
by the control box then adding a manual control across the relay could
be very dangerous...

I was going to use a momentary switch so I could stop it when I could
see it was at the desired height, but I will think more about that. I
will ask the seller but I expect they buy the boxes from someone else
and will not know about the circuitry.

If you're seeing sparks then they are coming from the contacts
themselves - which are on the mains side of the relay. Don't fit diodes
to these contacts - they won't last very long..... There might be some
point in fitting a high-voltage capacitor across the relay contacts....
but make sure it's one that's rated for mains use.

I'm not sure where the spark was coming from; I just know when the
relay switches off, it lights up blue for a fraction of a second.

It is a company selling doors, not someone just flogging an old one.
They have said they will post a new control box, though I worry will
the relay fail on that in time too?

On Thu, 20 Nov 2008 22:53:50 GMT, Harry Bloomfield
wrote:

Reverse EMF and the use of diodes relates to the coil side of the
relay, not the switching contacts. If the controller is designed for
the door, then the sparking can be disregarded.

If you are certain it is the relay to blame, then fit a replacement.

Thanks for all your help. As a replacement pcb is in the post, I shall
wait and fit that. I think the consensus is that the relay could be
replaced but with a minority thinking it is a bad joint on the pcb.
I'll have a closer look at the old board and relay once I have removed
it.

I'm not sure why I started rambling about diodes across the coil; I
guess I was typing faster than I could think! I know that the diodes
are on the coil side and I know that diodes would not work with ac; I
guess I was just in a panic when I typed it. Perhaps a snubber would
help but OTOH it's reassuring that you say sparking should be normal
and like you said, it was designed fore the job. The question is, was
it designed to last.

Thanks again.

HI Stephen

Stephen wrote:
On Thu, 20 Nov 2008 21:20:55 +0000, Adrian
wrote:

If all that your switch is doing is to short out the relay contacts then
it shouldn't do any harm.... but do you know how the power to the motor
is cut when the door is at 'full open' or 'full shut'. If this is done
by the control box then adding a manual control across the relay could
be very dangerous...

I was going to use a momentary switch so I could stop it when I could
see it was at the desired height

All sorts of safety implications, I'd imagine....
Does the door have some kind of switch / sensor on the bottom edge to
stop it from acting like a guillotine ?

, but I will think more about that. I
will ask the seller but I expect they buy the boxes from someone else
and will not know about the circuitry.

No - but it's up to them to make it work. If yours is failing then
you are probably not the only person with this problem - get them to
sort it out for you....


If you're seeing sparks then they are coming from the contacts
themselves - which are on the mains side of the relay. Don't fit diodes
to these contacts - they won't last very long..... There might be some
point in fitting a high-voltage capacitor across the relay contacts....
but make sure it's one that's rated for mains use.

I'm not sure where the spark was coming from; I just know when the
relay switches off, it lights up blue for a fraction of a second.

It'll be from the relay contacts - not the coil.
A good design will include a resistor-capacitor snubber to prevent this
from happening and prolong the life of the relay contacts. Again - not
your responsibility to fix it - and modifying it you'll invalidate
whatever warranty there might be and possible cause a dangerous situation...


It is a company selling doors, not someone just flogging an old one.
They have said they will post a new control box, though I worry will
the relay fail on that in time too?

Quite possibly.... g

Sorry to sound negative, but, unless you're confident that you know what
you are doing, you shouldn't really get involved.... (IMHO!)

Regards
Adrian

BigWallop wrote:

A relay will arc a little as the contacts make and break. It is why the
relay may have stuck in the first place, because the arc can cause a carbon
deposit to build on the face of the studs.

No. What normally happens is that localised corrosion sets in, and the
contacts don't 'make' properly. Its not carbon..its usually silver or
copper oxide.

The spark jumps the gap, and welds the things together. Usually leaving
a little 'pip' of metal.

Now knocking it may un-weld it, but the pip is there..a nice high
resistance point that will weld again.

Filing the silver flat gets you back to square one tho.