Elk 912B relay

[charliebarns]

I want to use the 912B relay in 24V mode to use as a trigger when the voltage trips it. However, my input source will only provide 24V at 5mA, and it appears the relay needs a minimum of 10mA before it trips. Is there any way I can modify the relay detect the trigger?

Thanks

CB

 

[Digger]

I want to use the 912B relay in 24V mode to use as a trigger when the voltage trips it. However, my input source will only provide 24V at 5mA, and it appears the relay needs a minimum of 10mA before it trips. Is there any way I can modify the relay detect the trigger?

Thanks

CB

The ELK-924 has a less than 2 ma requirement to trigger.

 

[BraveSirRobbin]

I agree with Digger.

Go with the 924 as it has lower voltage and current requirements for enabling the relay(s). It may be slightly more expensive, but will be worth it.

 

[charliebarns]

I agree with Digger.

Go with the 924 as it has lower voltage and current requirements for enabling the relay(s). It may be slightly more expensive, but will be worth it.

Thanks to both. I also contacted elk and they indicated the 924 will work but it will also need a constant 24V supplied to it as well as the trigger 24V. I'm confused about this. Why would it need a constant 24V source?

 

[Digger]

My guess is that the circuit needs a constant 24 vdc to energize the relay coil. The trigger current probably just turns on a transistor that switches the relay on. the low input current is because you are turning a transistor on and not powering the relay coil.

 

[BDHall]

One power source supplies the power to actually operate the relay and the other is used for turning the relay on and off or triggering the relay. This is useful where the control signal available has low current capability.

Depending on the application, another possible option might be a solid state relay which normally has a very low current requirement for control, often over a pretty wide voltage range such as 3-32 vdc. But be aware that the solid state relays normally have some leakage current when in the off state which can present some problems and some safety considerations at higher voltages. I would suggest reading up on the solid state relays before considering that option.

 

[charliebarns]

One power source supplies the power to actually operate the relay and the other is used for turning the relay on and off or triggering the relay. This is useful where the control signal available has low current capability.

Depending on the application, another possible option might be a solid state relay which normally has a very low current requirement for control, often over a pretty wide voltage range such as 3-32 vdc. But be aware that the solid state relays normally have some leakage current when in the off state which can present some problems and some safety considerations at higher voltages. I would suggest reading up on the solid state relays before considering that option.

Thanks everyone it's clear now. Now I just need to find a nice 24V power supply that I can mount in my enclosure!

CB

 

[nonumnos]

Thanks everyone it's clear now. Now I just need to find a nice 24V power supply that I can mount in my enclosure!

You might want to take a look at Elk's power supply offerings. The p124 (vs. the p124k which includes a can) should meet your needs.

 

[WayneW]

Thanks everyone it's clear now. Now I just need to find a nice 24V power supply that I can mount in my enclosure!

I am not sure that a 24V supply is needed. The way I read the 924 spec sheet, you can have 12VDC power the 924 and a trigger of anywhere from 5-24 VDC (including your 24VDC).

 

[BraveSirRobbin]

Can you provide more details of your setup? You should be able to use this as a normal relay with 24 volts to the coil (via connecting the "T" to the +24 terminal) unless I'm just not seeing something correctly here.

EDIT: I see what they mean now after re-reading the specs. The 'entire' board requires 60 milliamps so if you were to do what I said above you would need that amount of current capacity from the applied voltage.

 

[charliebarns]

Can you provide more details of your setup? You should be able to use this as a normal relay with 24 volts to the coil (via connecting the "T" to the +24 terminal) unless I'm just not seeing something correctly here.

EDIT: I see what they mean now after re-reading the specs. The 'entire' board requires 60 milliamps so if you were to do what I said above you would need that amount of current capacity from the applied voltage.

I picked up an ELK-924 along with an ELK-P124 power supply (24V) so I can provide a constant 24V to the relay. My occupancy sensor provides 24V out of it's blue wire when occupancy is detected, and stays on for a min of 8 minutes (occupancy sensor Leviton ODC20-UOW). However, the 24V is not energizing the relay. I have it hooked up to the T+ side of the relay. The relay specs say it needs 1.2mA at 12V, but doesn't state how many mA it needs at 24V. I'm wondering if this occupancy sensor is still not providing enough mA for the relay to detect the signal.... Any ideas?

CB

 

[Monk]

CB -
Did you cut the "24V OPEN" wire on the circuit board? It is supposed to be cut for 24V operation according to the instruction sheet.

 

[charliebarns]

CB -
Did you cut the "24V OPEN" wire on the circuit board? It is supposed to be cut for 24V operation according to the instruction sheet.

yup. Done. I'm getting both LEDs on the board on (AC and DC) but I think the problem lies in the 24V coming from the occ sensor...

 

[BraveSirRobbin]

I have it hooked up to the T+ side of the relay. The relay specs say it needs 1.2mA at 12V, but doesn't state how many mA it needs at 24V. I'm wondering if this occupancy sensor is still not providing enough mA for the relay to detect the signal.... Any ideas?

Are you only bringing one line (the "T+") from the Occupancy sensor to the Elk relay? It might not be getting any reference ground.

I would try bringing the power ground from the Occupancy sensor to the power negative (not the "T-") of the relay and see if that works.

 

[charliebarns]

I have it hooked up to the T+ side of the relay. The relay specs say it needs 1.2mA at 12V, but doesn't state how many mA it needs at 24V. I'm wondering if this occupancy sensor is still not providing enough mA for the relay to detect the signal.... Any ideas?

Are you only bringing one line (the "T+") from the Occupancy sensor to the Elk relay? It might not be getting any reference ground.

I would try bringing the power ground from the Occupancy sensor to the power negative (not the "T-") of the relay and see if that works.

Hey BSR,

I had tried that, sort of. there are 3 wires on this thing, red and black provide 24V and COMM, blue is the signal wire that has 0 potential when there's no motion, or 24V when there is motion. I've tried every combination of wires, but as soon as I touch anything to T- along with T+ the relays immediately fire, motion or not, and stay on. Heck if I short T- to T+ there's 24V over them and that triggers the relays. I'm lost at this point. I'll attach a pic of the sensor wires...

CB