Grrrr... that will teach me to buy cheap...

[Lazy-Ferret]

I wanted some relays to wire up the marker lights on the car, but as I wanted the side markers to flash with the indicators as well, I needed some relays with both normally open and normally closed contacts...

Had a look in Halfrauds, and they wanted between £7.99 and £10.99 each and I needed 3, so I decided to look on line to see if I could get a better price, after all, Halfrauds are not known for selling high quality stuff anyway. A quick search on Ebay, and I managed to get 5 for £6.49 with free postage, actually in the UK... Bargain... and even better they arrived the next day, nicely packaged, and each one in it's own box.

So today, I thought I would dodge the rain showers and pop out to wire up the lights. The circuit involves 1 relay switching the feed to the 2 others, so while not rocket science, I needed to pay attention as some wires swapped back and forward between the relays..

I wired it all up, and the lights stayed on all the time. I checked and rechecked my diagram, and the wiring, and it all looked OK. I started taking bits out of the circuit, connecting one section at a time, making sure it all worked every step of the way, then as soon as I put the final connectors into place, it just stayed turned on, regardless of what I did.

I have spent 3 hours going round and round in circles, only to discover that my "Bargain" relays, when you push the connector onto the centre N/O terminal, the terminal slides in a bit and shorts against the N/C terminal inside the relay housing, basically doing away with the whole system, and just connecting the lights straight to the power. A small tweak on the centre connector, pulling it back out after connecting to the terminal, and it all works...:doh

3 hours it took me to get to the bottom of this... it only took me 20 mins to do the wiring and connect them up the first time... the rest was spent questioning my sanity...

So the moral of this story is..........:doh

 

[rustic]

You could try CPCFarnell, google CPC, they sell all sorts. Switches, cables, relays, semiconductors, grease, caravan bits, car bits, tools, batteries, computer part, lamps, speakers, power supplies, cameras.
OK most stuff these days originates from China and the far east, but the quality varies, so worth going through a reputable company.
I have never had any issues with the products from CPC.:thumbs

In fact they are still advertising free postage via their website, type in WEBFREE in the comments box, and order on line, no minimum value at the moment.
I posted this a few weeks back, and they are still offering the free delivery.

I ordered some junction boxes, late yesterday afternoon, arrived today at 2:30 pm.

Excellent service.
Download their specials catalogues, some great prices.


If you buy cheap...
I have done it, I bought some panel mounted fuse holders recently from ebay... total cr*p, but I got a full refund.
What do they say... buy cheap, but twice.:doh


The other issue with your relays is probably that under load, the contacts will overheat, and melt the housing of the relay, causing potential shorts or worse.
I trust you have put suitable fuses in line, just in case of future issues.

best regards, Rustic

 

[rustic]

Re using 3 relays...

Why did yo have to go through a relay to drive a relay?

Could you have placed a couple of diodes in line with the coil, if say you are looking at say 2 sources to enable the lights.

This would prevent both circuits from feeding back to each other.
Less wiring and lower cost and more reliable, but not knowing your requirement, my suggestion is of course only a guess.

best regards,
Rustic

 

[Lazy-Ferret]

Thanks for the info...

Yes.. no problem with fuses.... great believer in them.

I did think of Diodes, but I needed a "Not" gate and decided I did not want to mess around with electronics to do it, so the easiest way would be with relays... Not only that, but I did not want to put any more lights into the indicator circuit, as it might mess up the flasher speed.

Basically, I have orange marker lights on the side steps... During the day when the side lights are off, they flash with the indicators, but at night they come on with the side lights. I wanted them to still flash with the indicators at night though, so have it now, where they turn off, when the indicators come on, and on, when they go off when the side lights are on, and still work with the indicators when there is no side lights..

 

[rustic]

Sounds really great, I assume the lights flash with the indicators and not opposite at night.

I bet Ryan will be adding these next... he likes to have something different.:thumbs

 

[96terrano]

I never use cheap relays, I get them out of scrap cars :thumb2

 

[solarman216]

You should have asked me, I have loads of car spec relays about you could have had for peanuts, Rick

 

[Lazy-Ferret]

Sounds really great, I assume the lights flash with the indicators and not opposite at night.

I bet Ryan will be adding these next... he likes to have something different.:thumbs

At the moment, they flash opposite at night, as I can't think of a way to do it so they flash with them at night... You would have to loose a flash somewhere. Might give it some more thought at a later date. Now I am sorting through my Dads old gear, I have found an assortment of 40XX, cmos chips, and some nice little 20amp PCB relays, so might have the bits to do it with a small electronics cct, on a bit of vero board at a later date

You should have asked me, I have loads of car spec relays about you could have had for peanuts, Rick

I didn't know I needed them then...:lol Will have to get some off you next time I see you, for "future" projects...:augie

 

[glanrichbex]

Relays are obsolete - FETs are much better :augie

This will switch 33Amps - totally isolated, no back emf from relay coils causing switch contact deteoration, no mechanical wear.

http://www.ebay.co.uk/itm/4-Route-M...423?pt=LH_DefaultDomain_0&hash=item3f14fdaf2f

 

[Lazy-Ferret]

Relays are obsolete - FETs are much better :augie

This will switch 33Amps - totally isolated, no back emf from relay coils causing switch contact deteoration, no mechanical wear.

http://www.ebay.co.uk/itm/4-Route-M...423?pt=LH_DefaultDomain_0&hash=item3f14fdaf2f

Nice... the only problem is you cant do change over with a FET, just on and off, so you would need more components to switch something off, when something else was turned on.

 

[glanrichbex]

Nice... the only problem is you cant do change over with a FET, just on and off, so you would need more components to switch something off, when something else was turned on.

You can do change over - either using 2 or 4 channels on this board or using P channel and or N channel FETS.

Relays are simpler to use but these days FETs are about 30p each where an equivalent relay is about £8. Relays are clumsey outdated mechanical devices which have contacts that oxidise and wear out. They also have an added issue where the coil produces a massive opposite voltage ( back emf ) which has to be suppressed otherwise it destroys silicon components such as transistors and integrated circuits.

FETs are amazing devices, the 'on' resistance of a FET from D to S is actually lower than two contacts of a relay so better power transfer, you don't get arcing when you switch them off, they require a few milliamps to switch them on where a 12volt relay in a car requires at least 100milliamps through the coil.

Once you've had a play round with them and realise how good they are, you'll never go back to using relays.