Doorbell and input voltage

I have a non-arduino processor and need help with connecting a doorbell to it. Below are the specs for the inputs on my processor. Can I connect the doorbell circuit to it directly (in parallel to the chime) or will i need some sort of a resistor in the circuit?

INPUT 1 – 4: (1) 5-pin 3.5 mm detachable terminal block;
Comprises (4) programmable digital inputs;
Input Voltage Range: 0 to 24 Volts DC, referenced to GND;
Logic Threshold: 2.5 Volts DC nominal with 1 Volt hysteresis band;
Input Impedance: 10k Ohms at >5 Volts, 1M Ohms at <5 Volts;
Pull-up Resistor: 2.2k Ohms per input


If it's a non Arduino processor, why the frik ask here? go to the forum that supports that processor, and stop wasting our time.

I asked here because the community has always been awesome and the question is probably pretty simple for a lot of the people here. It isn't a question on programming, it's a question about an electrical circuit. Unfortunately the processor is very proprietary and there is no forum support for it. Fortunately, Arduino folks are geneneraly really good at helping newbs with questions on low voltage circuits. My apologies if I offended you or anyone else on this board.

Input Voltage Range: 0 to 24 Volts DC, referenced to GND;

Can you measure your doorbell transformer output level? Also, the transformer will output AC, which you'll need to convert to DC.

I didn't realize doorbell circuits were AC. That being said I just measured it at 15 volts AC

KMtronic Ltd: Power Adapter: 9-12V DC to 5V DC for your ATMEL AVR or Microchip PIC project - would this connected to the doorbell in parallel and the 5vdc side connected direct to my processor work?

since the doorbell transformer probably has an isolated output an opto-coupler might be the best approach.



Not sure i understand your setup but.
Rectifying and smoothing the transformer may supply your processor.

For the bell i suggest you use a relay and the transformer for the bell circuit.
Some older bells had a double coil designed for AC actuation.
I cannot remember how they work though.

I don't want to power the processor from the doorbell circuit. The doorbell currently works just fine so I shouldn't need a relay at the bells. All I want is the to drive input 1 when the doorbell is pressed I can trigger a wav file to start playing on the mic input of my AV mixer and get laid over the HDMI audio stream (turning every TV in the house into a doorbell).

All I want is . . .

That's all?

That's all?

Well the only part I need help with is actually driving the input safely. The programming side in Crestron Simpl is easy.

Your pickup point needs to be across the chime. One wire is coming from the switch, the other side is going back to the transformer. Use an optoisolator for AC to pick up the switch closure. Then you can interface to output side to your processor. Need to make sure the doorbell button isn't lighted. The small current used to light the light may give you a false ON. It is not enough to drive the coil.

If your doorbell has a lighted push button, it is ALWAYS drawing current. Just not enough to ring the chime.


No lights on the button so I should be good there.