Volts,Amps,conversion,OhMy!

[Bear]

Hello All,
Have optoisolation relats rated at 1amp@48V.
? can I connect 1.3amp@24V.(and not let the
magic somke out)?
TIA
Bear

[MrBean]

I'm no electronics expert, but I'd say no.
If max = 1 Amp, then no matter what the voltage is you shoud not exceed 1 Amp, even if it's at 1 volt.

Terry.

[Al_The_Man]

If you are talking about the output (load) side, then Terry is right. But is your load 19ohms? If it is the output side, then the switching device is rated at 1.3amp regardless of voltage.
Do a calculation of current drawn based on 24v at the resistance of the load you are connecting.
Al.

[Bear]

Hello again,
Thanks for reply.I believe the load is the relay,marked 25V.@1.3,
power is from transformer @ 25V.50Va. Connection Im trying for
from transformer to relay to optoisolation switch back to transformer.
Optoisolation switch reads 1amp.@45V.max.Would I be able to put a
resistor or sumthing in line to reduce amperage?
Bear

[Al_The_Man]

If you are using a opto relay to pick up a magnetic relay and the relay is marked 25v 1.3 amp, that would be high for the coil current which is what you are going to switch, It maybe that the current capability of the magnetic relay contact is 1.3amps.
Measure the coil resistance of the magnetic relay to confirm the load.
For comparison, a 24v DC solenoid typically draws less than 1.3amps.
Al.

[Bear]

Thanks Al,
What kind of restance should I be looking for?
Bear

[Al_The_Man]

If it is a low power relay, I would expect 150 ~ 250 ohms approx.
Al.

[Bear]

Thanks Al, MrBear
Will work on this this week
Again , Thanks
Bear

[gar]

051211-2056 EST USA

Bear:

Something appears to be inconsistent here.

You might find a transformer labeled 25 V, but it is highly unlikely that a standard relay will be labeled 25 V instead of 24 V.

You also must distinguish between AC and DC relays. Typically an AC relay for 115 V will have about the same coil resistance as a 24 V DC relay, and will work as a DC relay at 24 V DC. A DC relay will not function on AC but will simply buzz.

Your opto isolated solid-state relay is probably only for switching DC circuits based on the specified maximum voltage rating.

Part numbers for your solid-state relay and the electro-mechanical relay might help. Also the physical size of the mechanical relay.

A DC output solid-state relay will not directly switch an AC load.

If I understand you correctly you have a transformer ( means an AC output ) with a voltage rating of 25 v ( probably at full load ) with a VA rating of 50 ( means about 2 A full load). Your use of period after V is confusing because it looked like 0.50 VA and that was not reasonable. You want to go thru a series circuit of a SPST switch to control an output power relay. At this point we do not know if the output relay is an AC or DC coil relay, its DC resistance, or coil power rating, or even if it is a 24 or 25 V coil. Usually relay coils are not rated in current. Also if you are talking about an automotive starter contactor, which is a short duty cycle device, the coil will be grossly different than a continuous duty relay.

If your output relay is something like a Potter & Brumfield KUP its size is 1.4 x 1.3 x 2.1 inches. The DC resistance of a KUP 24 V DC coil is 470 ohms. The DPDT version weighs about 3 oz without a socket.

If your output relay is an AC coil, then you need to use a solid-state relay like an Opto-22 OAC5 and its case is black.

.

[ViperTX]

Bear...draw a picture of what you're trying to do.....and give us a part number of what you have (opto-isolator, opto-isolated relay, Solid State Relay....etc.)

[gar]

051212-0902 EST USA

Bear:

More information on the P&B KUP relay.

At 24 V DC and 470 ohms the calculated current is about 0.051 Amps ( 51 milliamperes ), and the power dissipation is about 1.22 watts. An experimental test verifies the current.

For an AC relay of this same design the coil power should be about the same and thus the current.

If you have a relay with coil that runs about 24 x 1.3 = 31 Watts, then you have a relatively large relay compared to the KUP, or an intermittent duty relay like a car starter contactor.

For reference the contact rating on the KUP-11D15 is 1/4 HP or 10 A @ 120 V AC. The 10 A rating is a resistive load rather the 1/4 HP rating which is an inductive load rating.

To dissipate 31 Watts in a relay coil the coil has to be physically large. The KUP coil is about 0.9" dia. and 0.5" long.

.

[Bear]

Hello All,
Sorry for the delay,been busy,busy,busy.Anyhow back to relays,Dayton#5ZC07
Coil 24 VAC 50/60 HZ
Load 3AMP 4PDT
this is whats on the box,I ckecked the ohms,=.185k.
The transformer is from the original BridgePort(1 of the 3) the one I am using
is 440/220 3 Ph.primary .Secondary is 50VA 50/25/0,150VA 115/0,150VA 30/0.
Opti switches are inside control box from Low Cost CNC Retrofits ,paper flyer
that came with it reads max45volt@1.3 amps.What Im trying to do is make
the relay work(and keep magic smoke) through the opto relay in the control box.
I dont see anywere anything about amps on relay or relay box,is there a way to
make this mess work? appears i know enough to keep myself in a mess.
Again, Thanks ,and thanks for your patience.
Bear