fried relays

[fcky529]

on the 8 channel parallel board i fried channels 7&8 they are rated@10 amps, I was pulling under that,so i went to rat shack and bought some new ones rated for 12A but 9V coil, they seem to be working at the moment.

[fcky529]

and now channel 4 is starting to burn up(only four strings of 25 C7), I'm going to chock it up to cheap relays used in the assembly.

[NogginBoink]

Are they rated for 10amps AC or DC?

Is your load AC or DC?


If you're running, say, 10amps DC on relay contacts rated for 10amps AC, you could easily burn out the relay contacts. Without a zero crossing on the load, the contacts will arc much more than they're designed for with a DC load.

[fcky529]

10 amps AC @ 120VAC/ 28VDC/ 12VDV my load is ac as well

[fcky529]

IT HAPPENED AGAIN!!!

channel 4 burned up now and it's only running 4 sets of 25 C7's, replaced and done, but there is no way 4 sets could draw more than or even close to 10 amps.

I'm at a loss so i bought a couple of relays to keep around and I'll just keep soldering as they go.

[mac_man_luke]

is it still the original cheap ones that are going? if so why not replace them all

[NogginBoink]

Define "burned up" for us. Are you talking about the contacts or the coil?

[fcky529]

the contacts are getting hot to the point where it actually burns the varnish off of the coil wire and even melts the casing and once the casing melts the contacts get stuck in the plastic as it distorts and one of them actually welded shut. I'm thinking maybe just poor quality control during production. They're made by Songle. I'll include the link to them. The ones I got from rat shack seem to work just fine, like I said I bought a couple of them.

http://www.songle.com/en/prod.asp?action=one&pid=10

[pete]

hey,

Sounds like you are using mechanical relay. They are not designed to hold up in our application. you really need to go with solid state relays or a triac setup
to get any life out of them.

Pete

[fcky529]

i know i should, but this was the cheapest way for me to go for this year, next year I'm going to do something different.

anyone have a shopping list to make SSRs to replace the mechanical ones on the 8 chanel parallel board so I could replace them on the board I already have running?

[NogginBoink]

SSR's are pretty cheap. A dollar for an optoisolator, a dollar for a TRIAC, and a few pennies for 2 resistors.

[klanger]

What brand board is it, what does it look like, do you have a picture of both sides?

Kev

[fcky529]

it's the kit 74 board, the link to it is here

http://www.electronics123.com/s.nl/it.A/id.1712/.f?sc=8&category=35