ECN Forum Forums General Topics of the Trade General Discussion Area plug-in relay

Be careful with SSR's. If there is not a sufficient load/current draw it will not switch.
I have noticed over the years that when SSR's fail they usually fail in the closed position. SSR's are great in the right application.

I think you can find a cube that has a higher rating than 10 amps. But I have not seen or used one.
You can use a miniture (IEC) traditional relay, Then you can choose the one with the correct current requirement.

I like SSRs but I've never strung 400' of antenna on one and stuck it outside. Please remember that you have to worry as much about potential voltages across them when they're off, as load currents through them when they're on.
Joe

Thanks everyone, I do have a 30A Definite purpose contactor for the pump ( there's a thermal at the pump)
and I have replaced Crydom SSRs when they have gone bad, just never thought of it for these little loads. but I will remember these ideas next time

I did find a 12A octal and a 15A cube but that would need a different base.both have an LED and push-to-test button and they are about $ 5 from http://web4.automationdirect.com/ad...imers/15A_Electro-Mechanical_Cube_Relays

http://www.allelectronics.com/cgi-bin/item/RLY-482/500/120_VAC,_40_AMP_RELAY_.html

How about this one Tom? You can't beat it for $2.50 .
Joe

Holy Cow Joe, You just saved him a ton of $ I think the A-B that I used was around $12

what's next ?

Free ?

...that's a cool link I like the $.65 screwdriver testers, gonna order some

I like the Crydom or Opto22 that operate up t0 40a with the 3-32v input.
We used about 50 of them in a check sorter. I ended up with a big box of them.
Bear in mind this is just a triac with a LED optoisolator driving it so you can think of the input as nothing but a LED behind about 500 ohms of resistance. (they draw 5ma@5vdc measured and I am assuming 2.5vd on the LED, maybe not exactly true but a starting place)
You can drive 40a 240VAC directly from a 4000 CMOS gate, pretty cool. I always slip a 2n2222 or similar in there but that is just me.
I have also driven the pick of an SSR directly from 120v using the two capacitor and two diode trick. It worked fine for many years. That is something an old IBM engineer came up with to drive low voltage indicators with from line voltage, Basically you have a capacitor in series with the load and another one across the load for a voltage divider and filter. I added 2 diodes to protect the LED.

Greg I think I understand your circuit, just can't picture it..if you have the time, could you scribble the schematic and e-mail it to me ? and since I'm using the photoeye to turn the lights on I would need the cap diode trick as well since I have no idea what that is

http://www.opto22.com/documents/0859_Solid_State_Relays_data_sheet.pdf

OK, Here is the link for OPTO22's SSR datasheet. If you would choose to go the SSR route, I would urge you to carefully read pages 17 & 18. You will learn alot from those two pages. There is also some wisdom to be gained from getting burned by using the right part in the wrong application. I would guess a shorted output as your most likely failure mode.

If you ever have an application where it is essential to control AC within about an 8 mS window, look to SSRs first. Also, you have no contact bounce issues with SSRs. These SSRs have built-in snubbers which should help protect the output devices. But snubbers can fail too and can't be replaced if they're internal. External MOVs are a good idea.
Joe

If you are selling this you should just buy the 85-280VAC model.