alarm output voltage and current

[surveillancelot]

Hi!

I found out from older posts that it has been a mystery what voltages and current you can run through the alarm output (for example 2132). Has anyone found an answer? If not, I'll just use it to trigger a relay at 12V so it shouldn't require much current. But on the other hand, it would be so much easier if I knew for sure can I plug in sirens, strobes or other components directly.

 

[Michelin Man]

A couple days ago I replied to a thread about this.

It is a low voltage logic output. Normally floats (pulled up) at about 0.5v, then when an event is triggered it pulls down to almost zero I believe it was about 19mV.

You definitely cannot plug anything directly into the output, well it won't do anything but feel free to do so.

I personally wouldn't use it to trigger a relay, well for one it can't, and secondly even if you wired it up in series (which I don't recommend) you will probably blow something. Back EMF alone could kill the driving circuit.

 

[surveillancelot]

this makes me think why hell they even put the alarm output there. i would have assumed it's just a Normally Open circuit, and once the alarm is triggered, it closes (still there would remain a question how much current and voltage they can take). I will be taking off one camera next week and run some tests.

 

[alastairstevenson]

It is a low voltage logic output. Normally floats (pulled up) at about 0.5v, then when an event is triggered it pulls down to almost zero I believe it was about 19mV.

It's what's known as an open-collector output, it's not a relay with contacts like a PIR, it's a solid-state output.
When open, it will be pulled up to the voltage that the pull-up resistor in the alarm input of whatever you are connecting it to is supplied from. When closed, it will pull that resistor to ground.
When not connected to anything, it's effectively just an open circuit that will float around.

 

[Michelin Man]

^What he said.

Although what I said still applies.

They do make relay boards mainly for arduinos that will trigger when pulled to ground. It has all essential circuitry to trigger the relay. However it does run on 5v and I'm not sure if it will work without being pulled down to ground from 5v.

If I get time later I will test this out as I do have one.

 

[Michelin Man]

Ok, So I got round to trying a relay board meant for an arduino.

I'm glad to say that the signal from my 2132F-IWS is able to trigger the relay board. So it is an option if you do plan to use it. I can control the relay remotely via iVMS-4500 and obviously by an Alarm event.

However, the 5v supply that you use to power the relay board must be 'clean' without any ground loops and etc. Otherwise you may fry something, or in my case cause some noise on the mic circuit.

 

[alastairstevenson]

With your specific Arduino relay board, does it drive the relay directly or does the board provide a buffered input such as an opto-coupler?

 

[Michelin Man]

Yup, it uses an JC817 optocoupler to trigger a TO92 NPN transistor that powers the relay.

The other good thing is that these boards are cheap as chips, only a couple dollars each.

I was thinking of another way to power this relay board, and if I was to use it I'd probably use one of those TP-Link POE splitters since it has an output for 5V@2A, it is a bit of a waste but then again it seems like a good idea.

 

[romek77]

 

[alastairstevenson]

Thanks for sharing that.
Not to be too picky, but if your Q2 really was a PNP (as drawn but not as labelled) it would kinduv work like that, but would not be 'invert logic'.
If Q2 was drawn as an NPN with emitter at GND and collector to the relay coil, that would work OK giving 'invert logic'.

 

[aster1x]

Well spotted Alastair. I agree with your technical observation, the drawing of the transistor is wrong. In fact BC547 is an NPN transistor. So when the IN from the NVR is high, the optoisolator out is high, the BC547 base is high and the relay is energised and the LED2 lights. When the IN from the NVR is low, the optoisolator LED lights and the optoisolator transistor conducts and its collector is low, thus tuning off the BC547 and the relay is not energised dn LED2 is off.

 

[johngalt]

Do you have a link for the Arduino relay you used?

 

[Michelin Man]

Not anymore as I bought it a few years ago.

I'll find one for you now.

EDIT: Something like this should work: http://www.ebay.com.au/itm/1-Channel-5V-Relay-Module-Board-New-Style-for-Arduino-PIC-ARM-AVR-DSP-PLC-/171817058786?hash=item28011841e2

I'm not too sure if all of them are 'low' to trigger, some may be 'high' to trigger.

 

[Rellim]

Available as both High and Low trigger. I think Arduino is natively low trigger. Read the description don't just look at the photo ... don't ask me why I recommend this

 

[Michelin Man]

You can have it both ways, with the arduino you can have it go 'HIGH' or go 'LOW' it just depends on the device on the other side whether you want it to activate on a high (5v) or low (ground).

Hmmmmmm.

EDIT: http://www.ebay.com.au/itm/NEW-5V-1-Channel-Relay-Module-Expansion-Board-Low-Level-Trigger-for-Arduino-/381328909673

This one says it's a low trigger, which is the one you want for the camera. The other ones says driver current which I can only assume works on a high trigger.

Also just to add, even though the relay says it will do mains power at a fairly high current I probably wouldn't advise you go anywhere near that current.