So my doorbell circuit, oddly, runs 24 vac until you press the doorbell, when the voltage drops? I was planning to monitor the circuit in an open state and have my arduino report if/when the circuit closes. Now I'm in need of monitoring the voltage I suppose- if/when the voltage drops from 24 vac to below 20 vac, I'd like arduino to then report.
Thoughts on how to most efficiently monitor low ac voltage on a circuit like this?
Thanks
Hi,
What is the frequency of the AC waveform? If it is slow enough, you could probably use a potential divider to divide the AC voltage down from -24V/24V to -5V/5V and then use a rectifier to get rid of the negative voltage and read straight into the Ardunio analog in and perform digital peak-detection.
However, if it was me, I would simply attach a microphone, preamplifier and amplifier and use that to detect the doorbell sound instead of tapping off from the AC voltage...
60mhz ac
re: microphone / preamp / amp- sounds a bit complicated? Surely, there's a simple way to monitor fluctuations in vac....
If this was my project, I would put a 24 volt SPST relay in parallel with the door bell and use the relay closure as a push button switch connected to the Arduino.
Paul
60mHz? :o
Sorry- 60 hz
I like the SPST relay idea- where can I get one of those and what would be the best way to set it up? Can you get them to run on a 24 vac circuit or do they need more than that?
Thanks
Just a thought- why not monitor current? Flow should be much higher on ring (button push) than not?
Arduino max current is 5v input, so you'd need to get resistors involved to reduce the constant 24vac and I don't even know if an Arduino can handle ac to begin with...
stgeorge:
Sorry- 60 hzI like the SPST relay idea- where can I get one of those and what would be the best way to set it up? Can you get them to run on a 24 vac circuit or do they need more than that?
Thanks
I see one on EBAY for $3.50, free shipping. Connect the coil of the relay to the same wires going to the door bell. Connect the relay contacts to an Arduino digital pin with the internal dropping resistor set on. Program the Arduino just like for a push button.
Paul
Thanks- firstly, can you give me the specifics on that relay that you are seeing? Maybe an ebay item # ?
Secondly, pardon but I'm pretty new to this Arduino and am not yet familiar with "the internal dropping resistor set on"- can you elaborate?
Thanks for the help, I think this may very well be the optimal solution.
stgeorge:
Thanks- firstly, can you give me the specifics on that relay that you are seeing? Maybe an ebay item # ?Secondly, pardon but I'm pretty new to this Arduino and am not yet familiar with "the internal dropping resistor set on"- can you elaborate?
Thanks for the help, I think this may very well be the optimal solution.
Search EBAY for: relay 24vac. Look for the cheapest price. It may be a two pole relay, but you can use just one for your project.
For the digital pin and internal dropping resistor, you need to study up on the Arduino documentation and example code.
Paul
What do you mean by MOST EFFICIENT.
Do you mean cheapest or really most efficient
I guess I mean all of it- efficient with resources...time, money, programming hassles, etc...
Regarding the ebay relay- I guess what I worry about is that this simple little doorbell stepdown transformer isn't putting a lot of amperage out on the circuit at 24 vac, so I worry it won't be enough to either pull the coil or hold the coil closed as the case may be....
Incidentally...this restriction of not allowing posts within 5mins of another is pretty silly, isn't it?
stgeorge:
Incidentally...this restriction of not allowing posts within 5mins of another is pretty silly, isn't it?
No, it's the best we can do at the moment to prevent spam.
Sorry you're inconvenienced.
AWOL:
No, it's the best we can do at the moment to prevent spam.
Sorry you're inconvenienced.
It would be great though, if one could edit posts without having 5 minutes to wait.
BTT: I would use a diode, to get rid of the negative voltages + a voltage divider to reduce the voltage to <5V.
Then average the voltage over a period of ~50ms, problem solved.
lg, couka
Hi,
If your doorbell is an electric one, ie 24Vac transformer and a simple bell ding/dong and switch then when you add a relay you will be drawing current through the bell coils.
So a relay that is 24Vac Coil with >1K resistance, to keep current down, >2K will give you 12mAac.
Does your doorbell button have a light in it that goes out when you press the button?
Tom.... 