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ELK-930 with an electronic doorbell

pgaylord

New Member
I have been  using an ELK-930 for some time to detect when the doorbell rings, and it's been flawless.  Unfortunately my old doorbell just died and I had to replace it.  The old one was mechanical with a solenoid that would strike a metal bar for the sound.  The new one is fully electronic with no mechanical parts.  The ELK-930 does not detect the doorbell button push anymore, and I'm pretty sure it's because the new doorbell doesn't draw enough current (900 mA minimum is what the manual states).
 
Does anyone know how to get around this?  I'm thinking I could put a resistor in series to force more current draw, but my electronics knowledge has faded over the years and can't remember how to calculate the appropriate value resistor, or what power rating I should choose.
 
Any ideas?
 
 

RAL

Senior Member
To increase the current draw, you need put a resistor in parallel with the doorbell. Putting a resistor in series would reduce the current, not increase it.
 
If you have a 16 Volt doorbell transformer, this would require about a 15 ohm resistor.  If you have a 24 Volt transformer, then you would need about a 25 ohm resistor.
 
The resistor should be high wattage, at least 20W for 16V and 25W for 24V.   You might be tempted to substitute a lower wattage resistor since the current should normally just be momentary.  But if the doorbell button ever gets stuck, it could become a fire hazard.
 
https://www.amazon.com/dp/B015Z18EO2
 
https://www.amazon.com/dp/B015Z1964O
 
Of course I'm slightly bleary eyed from a long weekend, but I think the resistor would need to be in series with the doorbell button and one leg of the trigger to the chime. The pushbutton is NO (or very close to it depending on if it is lighted or not) because the button, when pressed, is a short circuit as far as the chime is concerned (well, actually just completes the circuit).
 
The resistor in parallel would be negated upon the button press.
 
Sorry, too lazy to work out the calcs at the moment.
 

RAL

Senior Member
Hi DEL - haven't seen you around in a while!
 
I guess whether you view it as series or parallel depends on what you are describing.  When I said the resistors go in parallel, I meant in parallel with the load of the doorbell.  But I think your view is that the resistors (and the doorbell itself) are in series with the doorbell switch, which is also true.  
 
Here's a picture of what I mean.  Resistors are in red.
 
index.php
 

ano

Senior Member
In theory that would work, but you would need a 18 ohm resistor to generate the required 900ma.  That isn't a big deal, but this resister would need to be 20W for safety, which is pretty hefty. Maybe instead just find a relay with a 16VAC coil voltage and use the contacts to connect with a panel.
 

RAL

Senior Member
ano said:
In theory that would work, but you would need a 18 ohm resistor to generate the required 900ma.  That isn't a big deal, but this resister would need to be 20W for safety, which is pretty hefty. Maybe instead just find a relay with a 16VAC coil voltage and use the contacts to connect with a panel.
 
Are you suggesting the OP abandon the Elk930 and electronic doorbell and instead use a relay connected to the doorbell button to activate an input on the alarm panel?   I don't think he wants to lose the function of the doorbell.
 

ano

Senior Member
RAL said:
Are you suggesting the OP abandon the Elk930 and electronic doorbell and instead use a relay connected to the doorbell button to activate an input on the alarm panel?   I don't think he wants to lose the function of the doorbell.
The relay coil would be wired in parallel with the actual doorbell. Press the button and the doorbell rings and energizes the relay. Not terribly complicated. The ELK-930 is designed to operate with a solenoid-based doorbell, which the OP no longer uses.
 

RAL

Senior Member
ano said:
The relay coil would be wired in parallel with the actual doorbell. Press the button and the doorbell rings and energizes the relay. Not terribly complicated. The ELK-930 is designed to operate with a solenoid-based doorbell, which the OP no longer uses.
 
The problems that I see are:
 
- Relays with 16VAC coils are not very common.
- You would need a relay with a coil that pulls about 900 mA. That means a coil with a fairly low resistance, which is not your typical relay.  Most small relays have coils in the range of hundreds of ohms.
- If you do find such a relay, it's going to dissipate 15-20W, same as a resistor.
 
I would just keep it simple and use a resistor to make things work.
 

ano

Senior Member
RAL said:
The problems that I see are:
 
- Relays with 16VAC coils are not very common.
- You would need a relay with a coil that pulls about 900 mA. That means a coil with a fairly low resistance, which is not your typical relay.  Most small relays have coils in the range of hundreds of ohms.
- If you do find such a relay, it's going to dissipate 15-20W, same as a resistor.
 
I would just keep it simple and use a resistor to make things work.
Not true. Why would the relay need to draw 900 ma or dissipate 20W?  The one offered above would work great. The ELK-930 would need to be removed, and it the new relay added. Depending on where the original wires went, you would need some slight rewiring.
 

RAL

Senior Member
ano said:
Not true. Why would the relay need to draw 900 ma or dissipate 20W?  The one offered above would work great. The ELK-930 would need to be removed, and it the new relay added. Depending on where the original wires went, you would need some slight rewiring.
 
Ok, I misunderstood that you were proposing to substitute the relay for the 930.  You could do that, and you're right, then there would then be no need to draw 900mA.  
 
But then you might encounter a new problem, which others here have run into when they tried using something other than the 930.  That's the response time of the panel to the button press.  Not everyone who comes to the door presses the button for a long enough time for the panel to recognize the closure.  Some panels, like the Elk, allow you to configure individual zones for fast response, but other panels may not have that capability, or only change it on a global basis.
 

pgaylord

New Member
Thanks everyone for the great suggestions.  Right now I'm leaning towards the relay option by ano.  Still thinking through the options.  I will certainly post back my results.
 

ano

Senior Member
RAL said:
Ok, I misunderstood that you were proposing to substitute the relay for the 930.  You could do that, and you're right, then there would then be no need to draw 900mA.  
 
But then you might encounter a new problem, which others here have run into when they tried using something other than the 930.  That's the response time of the panel to the button press.  Not everyone who comes to the door presses the button for a long enough time for the panel to recognize the closure.  Some panels, like the Elk, allow you to configure individual zones for fast response, but other panels may not have that capability, or only change it on a global basis.
That is true, but a relay may provide a slight delay to extend the pulse a bit. The relay BraveSirRobin suggested looks even better because it contains a capacitor to extend the pulse a bit further.  I did something similar but used an HAI/Leviton, and don't know of any instances when it didn't work.  If it was just the button, that would be a problem, but relays aren't really quick.
 

BraveSirRobbin

Moderator
I'm not familiar with the Omni, but I do know the Elk M1 has a 'fast response' option.  If the Omni has such maybe try that if the inputs don't pickup the relay contact closure
 
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