Fitting Relay snubber.

Please understand I have ZERO electronic knowledge.. First post requesting spelt out advice.

I have written a software program which includes the switching on/off of mains lights. Using UDUN 8R relays (purchased from Audon Electronics). Eventually, I got everything to work.

Problem is, lights are fluorescnt tubes. (125 watt). Apparently, ALL I need to do is put a "snubber" across the contacts to avoid the problem of induction load.

Everyone says it is simple. No one can tell my where I can get it dome.

Any help, please?

A snubber in this case is just a resistor and capacitor in series, wired across the relay contacts. You can buy them ready made as a single component with two wires. All you do is connect one to each side of the contacts.
The idea is they absorb the 'kick' of energy that might be produced as the contacts open, preventing or at least reducing the chances of sparking. This prolongs the contact life and helps to reduce the 'click' of radio interference that would be caused.

Typical values are 100 Ohms resistor and 0.1uF capacitor with a 250V or more AC voltage rating..

Brian.

Many thanks for your response. Much appreciated.

Trouble is I have been told that's all I need but for example, when calling RS Components and explaining for 125 watt tubes, they say they need to know "Capacitance". I do not know what that is and they say they cannot tell from watts. If they do not know, how would I ever know? In other words, how do I find out precisely the "snubber" I need?

Bob.

My friend, If you are not that speciallsit of electronics, use the suggestion you received.
Snubbers are usually being used for protecting of the contacts of the relay (your case here).
There are some calculations that you dont seem to be likely to do, but what Brian suggested is good enough to handle what you need.
By the way connect the resistor and the capacitor and connect it to the contacts in use.

Mahdi.

From RS, the part number you are looking for is 672-7032.
Snubbers cover a huge range of switching and arc suppression uses so it's not surprising they couldn't advise on your special need.

Brian.

Many thanks for your kind assistance and guidance.

I do not know how to solder (? I presume) but will certainly purchase the devices and find out how to achieve the next step.

Bob.

I will suggest use of diode in reverse bias in series with parallel combination of RC.
It will allow you to select low value of parallel resistor and also resistor will not consume any energy during normal operation. Find schematic attached.

I think the diode suggestion is for something else. Stick with the idea of putting the snubber across the contacts, from the input contact to the output contact, not across the incoming power or across the feed to the lamp.
If you have a two-pole relay, meaning two switches operated by a single coil, use two snubbers, one across each of the in/out contacts.

Brian.

The Udin-8R (User manual: **broken link removed**) contains Tyco PCN-105 relays. They are single pole single throw (SPST) as shown in the Udin manual. You can view specifications here: PCN-105D3MHZ,000 Product Details - Tyco Electronics. Since these are soldered to the printed circuit board inside the Udin-8R with little room to spare, the best place to mount your snubbers would be on the screw terminals.

You may have to create a pigtail assembly with some solder and shrink tubing or even mount an auxilliary terminal block to safely accommodate the snubbers.

Many thanks for your contributions. Much appreciated.

Manojdharap:- Looks great but absolutely no idea what diagram means. NO electronic knowledge but thanks.

Brian:- Have ordered the snubbers you suggested from RC Components but out of stock until 1/11/2010. Taking a gamble.

KJ6ead:- I think I understand snubbers must be fitted to contacts and will wait until they arrive to see if I can fit them.

Since you have been so helpful, I wonder if you could advise further?
Audon have been less than helpful. Originally they said each relay would operate eight lights indepentantly and SPST seems to imply that. However, an electrician reckons they will only work in pairs! Each pair of relays has THREE contacts. Certre one for a common wire. Audon will not even answer emails and I spent over £300 with them. Currently in talks with a American suppier of a simillar device.


I get 8 clicks when each relay is activated but he insists I wont get 8 individual controls. Not actually been able to physically test.

Trouble is my ignorance of the workings of the units. It took me a long time to learn how to program them.

Thanks again for your interest.

Nothing has changed, you still need the snubbers as before.
According to the data sheet, you have 8 individually controllable relays which is exactly what you want. The only thing you have to be careful of is that you don't have access to all the relays individually. They can be switched on or off independently but they are grouped into four groups of two with one connection common to the pair of relays in each group. So to wire it up, assuming you are working from a single AC mains supply, link the common pins together (the sideways 'T' arrangement in the data sheet diagram) and feed the power into them all simultaneously. Take the feed to the lights from the other side of the relay switches (the 8 pins with a 'drawbridge' symbol on them) one to each light fitting. The other side of the lights are all joined together and returned to the AC power source.
Assuming you are in the UK, it would look like this:

Mains Earth (Green/Yellow) - connected to the earth terminals on all the light fittings
Mains Neutral (Blue) - connected to the neutral terminals on all the light fittings
Mains Live (Brown) - connect to the four 'T' terminals on the relay and to one side of the eight snubbers

The 8 relay outputs go to the other side of each snubber and to the Live terminal on each of the lights.

Brian.

Brian,

I cannot express my thanks for your detailed assistance.

I have no clue how to acheive this even although you are highly explicit. It certainly looks very logical to me and I will pass these comments to the electrician who will surely understand.

Fantastic! Thank you.

Bob.