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March 24, 2020 13:48

Volt free N/C to switch 230vac strobe light

HI Guys,

Really hope someone can help me here ?

I have a control panel that comes pre wired giving a 2 core cable to signal for a fault.

The signal is volt free and normally closed.

I require the volt free signal to switch on a 230v mains powered small strobe type light when a fault occurs. The application is for domestic residences and the strobe light wired from either lighting circuit or smoke alarm circuit.

Basically i need a switched input module of some description i think !

Does anyone know of a module and strobe i could use ?

P.S if the module itself had an LED to alert the fault that would work instead of the seperate strobe.

0 Votes


March 26, 2020 12:17

I think I'm interpreting your problem differently than Boss.
It sounds like you just want a circuit that will turn on the strobe when the fault output from the control panel goes open circuit.

One question is what the rating of the fault output signal is.
How much current can it handle, and what maximum voltage can it handle?

Case 1: It is an isolated relay output rated for 230 VAC.

Case 2: It is a relay output, isolated, likely to handle a reasonable current, but limited output voltage.

Case 3: It is an open collector transistor output, which would be polarity sensitive and probably limited to 12-24 VDC maximum voltage it can handle, and at a relatively modest current.

For case 1, you could just use a relay with a 230 VAC coil and at least one SPDT normally closed (NC) output contact. Wire the fault output circuit in series with the relay coil, across the 230 VAC supply. Wire the strobe in series with the relay NC output and COM contact, across the 230 VAC supply. As long as there is not a fault, the relay will be powered on, and the relay's NC output circuit will be open, keeping the strobe off.
If there is a fault, the control panel output will interrupt power to the relay coil, the relay will go to its normal (unpowered) state, closing the connection from the NC to COM contacts, and powering the strobe.

For cases 2 and 3, use an AC->DC power supply to get 12VDC. Use that to power a 12VDC coil relay with SPDT NC output contact. As long as you choose a relay with contacts rated for 230 VAC and at least the current rating of the strobe, you can use the 230V strobe. Or you could use a 12V DC powered strobe, or LED, in either case wired in series with the relay contact and the appropriate power source. (If the LED is rated less than 12V, you will need a resistor in series with it to limit the current to its rated value.)

You don't say whether this is a one-time project and what sort of mounting / wiring method you are using, so I haven't addressed that aspect. (Depending on what country you are in there are also applicable standards that may need to be met if this is for safety-critical circuits, especially in commercial buildings.)

0 Votes

March 25, 2020 08:28

I think you can just use a normal strobe, you could use a mains powered strobe or a low voltage strobe which may be better for containing the mains voltage to one area and have a low voltage routed to the strobe location.
The attached image shows both options, the first just requires wires and a strobe the second a PSU and the matching voltage strobe.

0 Votes