Hello all, I've recently acquired some 5V relay modules for use in a project. On top, they list the max
voltage as being 250V at 10A and 125V at 15A. I recently got some rope LEDs, and I measured the
voltage on those as around 440V AC, but I didn't get a reading on amperage because my Multimeter's
fuse is a dud. What I'm wondering is, since the amperage on these lights can't be that high, can I still
use the relays to control them, or would that damage something internally on the relay?
I think that the voltage would be the limiting factor here. The relay contacts have to be far enough apart, when the relay is open, so that they don't arc. Spacing that works at 220V can't be guaranteed to work at 440V. I would not use a component outside of its known specs.
if the relay specification is 250V maximum I would not recommend operating it at 440V
I would suggest you get a 3 phase relay rated at 415V and use the 5V relay to switch it
Alrighty then, thanks guys! I guess I'll just figure something else out then.
thinking again 440V is very high - what is driving the rope LEDs?
While the relay specs may state 10 or 15 amps, your circuit board traces will certainly not handle that.
Paul
DangerouslyExplosive:
I recently got some rope LEDs, and I measured the voltage on those as around 440V AC
What ?
That makes no sense at all. Please explain.
Yours,
TonyWilk
I also doubt that you have 440VAC. LEDs are low-voltage and they run from DC, although you can string them in series for higher voltage. Did you measure that with the LEDs connected?
If you have a special constant-current power supply you can get high voltage, especially with no load connected. And it may be pulsed or PWM (which has an "AC component").
But, you should NOT switch a constant-current source with a relay because it's trying to push current through an infinite resistance (which requires infinite voltage). You can "stress" the power supply, and who-knows what else...
DangerouslyExplosive:
I recently got some rope LEDs, and I measured the voltage on those as around 440V AC,
WOW, what rope LEDs run on 440Vac, it sounds like 3phase power, if so you will need to totally isolate the LEDs when you switch them OFF.
In other words switch BOTH leads to the LED rope, not just one.
If you switch one lead, the LED rope will still be at a phase voltage above ground.
Tom... 
DangerouslyExplosive:
Hello all, I've recently acquired some 5V relay modules...voltage as being 250V at 10A and 125V at 15A.
Don't confuse the rating of the relay with the rating of the circuit board.
Many relay boards are not designed (dangerous) for mains power.
Leo..
Sorry it took me so long to reply, but the 440 volts AC was admittedly measured without a load. My bad. With load it's much more reasonable, but I originally took the 440 at face value because the power cord is just a plug with what appears to be a small transformer (up or down, I can't tell) and the part that goes to the LEDs, which have lots of resistors along the strip. The strip itself is actually AC, the LEDs are arranged in such a way that they act as their own rectifiers.
As for the relay circuits, the traces do appear to be designed for AC power from the mains (very thick and widely spaced), so I just cut up my strip into sections and got a few more power adaptors (because I need the LEDs sequenced) and I'm just turning on and off the power before it gets adapted for the LEDs. Seems to work fine for now, and I'm not running huge strips or leaving my LEDs running for long periods, so heating from current isn't an issue.
Thanks for all the input!
-D.E.