Build A Contactor/relay

[scraglor]

There's enough power in the solenoid coil to break a small weld but not the spring. So what I did with my diy contactor was have the solenoid pull the contacts open for lights off, rather than the spring. Also lets me run stuff during lights out by connecting it to the timer. (Which is on during lights out.)

was that a relay though? only problem i see with that, is there shouldn't be any welding, and although it's now capable of breaking the weld, if there is any, you're adding to contact resistance each time. Your relay never gets stuck on, but you could be slowly building up a volt drop across the contacts and they'll just burn out rather than stick on

I also fitted a quencharc across the contacts, reduced the arcing heaps. Maplin call them something else, I forget. It's a 100R resistor in series with a 0.1uF capacitor. I'm making another contactor for the veg tent plus 1 as a spare. Is it ok to diy the quencharc? I've got 3w wirewound resistors, no voltage stated and 0.1uF 400v capcitors. Can't think of a reason they wouldn't work but thought I'd ask first.

i think quencharc is a brand name, usually just called arc suppressors. don't see why you can't make you're own? as for the wire resistors, resistances have no voltage limit generally, as long as you don't over heat them during continuous running, so (240v / sqrt(1/(2pi.f.c)² + (R²))²x R = watts

http://www.paktron.com/pdf/Quencharc_QRL.pdf

that'll give you all you need to know about quencharcs on page two, don't ask me for help with the differentiation/intergration though . also you'd need to measure the resistance of your ballast and work backwards using the current to find the inductance in henries unless you can find it published? unfortunately accurately choosing a quencharc isn't as easy as just picking one from a table.

easy enough just to guess though, only thing i'd be concerned about is inrush current, as the quencharc is only really good for welding on opening and are used for relays for closing large contactors, i.e. purely inductive, and is just adding to the problem of inrush current.

Any chance of a list of brand name contactors with model numbers and the lighting they are suitable for please? Would be cool to have a sticky to reference...these contactors are suitable for 2 x 600w: a,b,c etc.

don't know off the top of my head, all i do is just check the data sheets when anyone asks, i use an MK sentry contactors myself, 20A up to 800w 40A to 1600w, bit pricey though or telemecanique motor contactors, cos they're free merlin gerin publish all the lighting capacities of their contactors, but for some reason rs don't put the bloody data sheets up any more? maybe when i got a bit more spare time i'll do a bit of a hunt around.

just looked at that contactor bob, and that's actually one of the tel mec ones i was reffering to earlier, top quality, bit pricey, but good for 1 600w per pole, and no doubt you can pick one up off ebay cheap

Edited November 3, 2008 by scraglor

[bobhope]

thanks for the advice, I was planning to use it to switch 3 600s double pole

and then use the 2 N/C contacts for my heaters at night.

the picture only shows 2 poles but it is actually a 4 pole 2 N/C 2 N/O

I want to get this right as I've been running it off a 30A relay from maplins for years,

then read a thread you contributed to and bucked my Ideas up.

sorry to hijack this thread by the way I can push off somewhere else if more convenient

[scraglor]

why not, get a three pole NO contactor, 1 lamp to each pole, and use the auxillary contacts for your heaters.

for you bob, i'd use this one, the auxillary contacts are good for 10A current, and will be fine for any small inductive loads you may wanna add, as they're designed for control, which means basically switching inductive loads, i.e. other relays/contactors and are rated for high inductive loads

http://uk.rs-online.com/web/search/searchB...t&R=6089425

and for growguy, the one posted by bob, as this will be good to flip flop between rooms

http://uk.rs-online.com/web/search/searchB...=4547913#header

i'd have a look on ebay, there's loads on there, no point paying full price

[bobhope]

excellent thats perfect

should i run the three terminals back onto one extension lead, or use seperate leads,

and wouldn't it mean not switching the neutral,

I thought I read earlier that there was still a possibility of danger from the neutral

this is very helpfull

[bobhope]

sorry just spotted all the other terminals should have looked properly before posting

[scraglor]

don't switch the neutral, there's no need, there's no danger from it. in fact switching the neutral with a portable piece of equipment actually increases chance of shock, because by switching the neutral open you remove all paths to earth for the capacitor to discharge, so when you unplug it, if you're unlucky enough to touch one of the plug terminals then you're gonna get a jolt off the capacitor, if you leave the neutral made then it will discharge to earth potential.

so just switch each live through an individual pole to an individual socket, up to a max of about 1kw per pole, probably safe up to higher loads, as these are good quality industrial contactors, but 1 kw per pole is a good safety margin i'd say.

switching both live and neutral is essentially the same as running extra contacts in series (as has been pointed out as something to do in other threads), so you increase the breaking capacity of the contacts (but not the current rating) the load is in series between the two sets of contacts (live side and neutral side) but this makes no odds, it's the same as having both sets of contacts in series on say the live side, it's just convenient to switch both wires. as the load is being shared by the individual poles in this case, you would have to have individual poles to break the neutral for each live pole, otherwise you'd have three times the current through the neutral pole, as you'd have all the currents from each live pole sharing the same neutral.

e2a: if you want to share the load between poles in this way, you have to always go to totally seperate individual sockets/loads. if you feed them all back to eachother to a single outlet (a 4way extension is still a single outlet because each socket shares a common live and neutral) then what happens is, when the contactor is closed, everything is fine and the current is split between each pole, but when the contactor opens (and also on closing) each pole doesn't open at exactly the same time, it's may only be a fraction of a second, but electricity moves at close to the speed of light! so the last contact to open has to break the full load current, which obviously defeats the purpose of splitting the load in the first place. if each pole goes to an individual socket then as soon as it's open, current stops flowing through that load and that's the end of it, doesn't matter if they open at the same time, and it doesn't matter if they share the same neutral, because if they do then you don't switch it. if they have individual neutrals (determined by how many poles your contactor has) then by all means switch the neutral too, as this helps stretch the arc on opening and helps save the contacts..... although as i pointed out earlier, in portable equipment with fairly large capacitors in, this isn't always such a good idea if there's a chance you may unplug it while it's still charged

Edited November 3, 2008 by scraglor

[bobhope]

thanks Scraglor excellent and clear advice .I'll get moving on this as soon as it's back in stock.

it'll give me a bit more peace of mind.

Its also made me realise the poor quality of a lot of shop bought kit after opening up some of their

products

[Nocebo]

hi,

i wonder if i can get some help please?

ive made a contactor relay like the one at the start of this thread.

it all worked fine and did the job, but after five days i checked to see how things were

going and the light was on when it shouldnt have been giving my plants 24 hours of light in the last few weeks of flowering.

i checked the timer and that was off. the remedy was to press the `test` button on the relay.

everything worked fine for another four days then it happened again! another 24 hours of light. pressed `test` again.

i have a 400w hps. this relay: relay

id like know whats going wrong, and what i should be doing to stop this happening again. also will the two periods an 24 hour light cause any problems?

thank you.

[scraglor]

it's your relay buddy, not rated for the job i'm afraid. what make/model is it? to help in the meantime, connect another set of contacts in series. i.e. at rather than going in one side and out the other to your lamp. go in one side, out the other, then back into another set of contacts, then out the other side to your lamp. this is only a temporary measure. i posted ages ago when i first saw this thread that relays shouldn't be used. should be removed from the sticky's imo

[Nocebo]

thanks for the reply scraglor,

i think ill get one of those cotactors you mentioned. what one would be best for my light?

also are there any wireing diagrams?

thanks for the info.

[scraglor]

you shouldn't need a wiring diagram, simple as. ebay is the best place to get cheap contactors, as there's always people selling unused parts from jobs, and they're good industrial grade components. have a look for one that tickles your pickle, pm me a link and i'll tell you if it's up to the job or not

[The Villan]

I think I will buy one ready made

[madazz]

hey scraglor,

hey mate was after some help building my light switch gear box. i have a Telemecanique contactor , circut breaker, (5 min) lock out timer (solid state relay), and a grasslin panel mount timer. i've drawn a diagram can u please help and show me how to wire it up. I live in Australia our power at the powerpoints/mains is 240vac 50hz. I have a bit of a idea but i'd like to make sure i do it right. My contactor is 7.5kw. prehaps u can email me

s11.mitchel@yahoo.com.au and send me the pic back with the right colour wires? Please!!! this will all be mountd in a pvc enclosure.

Many thanks really appreciate your help!!

Madazz

[scraglor]

what's the make/part no. of the ssr? also bit confused on the timer terminals, can you reproduce the wiring diagram for the timer?

[Guest cantharis]

In my case I run 1 x 400w HPS, I know the INDUCTIVE load is 3.15 amps at switch on. Ask the manufacturers of your light for this info.

I wonder, what will be the induced voltage across the contacts at switch off??