Photon + 220VCA MOTOR

I want to connect a Particle Photon to a “Normally open” contact of a timer which controls a 220VCA.

My question: Sholud I add Resistor and Capacitor (pullup) for avoiding debouncing or it is not neccesary?

other question: is Photon susceptible to electromagnetism for working on HIGH VOLTAGE LEVELS (220VCA devices)?

Thanks for all your recommendation.

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You must not directly connect the 220VAC neutral line to the Photon at all!
This looks rather hazardous - no resistors nor caps will protect you from that.

Apart from the general no-no of that, there is one very explicit danger in that.
In a three-phase grid one phase can get damaged while the other two phases are still intact. In a compensated grid the neutral point isn’t necessarily rigidly grounded (TN grid vs. TT grid) but “floats” symmetrically between the available phases potentially resulting in some considerable voltage between the virtual neutral and your local ground level.

You would need some timer that has two electrically isolated contacts or you can do an indicrect measure e.g. by means of inductive current sensors.


That wiring does not look like three-phase and I totally agree with @ScruffR’s comments regarding the neutral wiring. You may, as he pointed out, use a non-contact (isolated) current transformer to measure the current to the motor. Or, perhaps the timer has an LED which you can sense. Whatever you do, it needs to be fully isolated from the motor’s circuit.


@jonamleonel, you might want to consider using something like a Dwyer Instruments CCS-221100 to detect current in the motor circuit. I find this also beneficial in that you know the motor is actually drawing current, not just that the timer has attempted to run the motor. The device provides the required isolation and is powered by the motor’s circuit. Therefore, the installation is pretty simple and safe. Use either a pull-up or pull-down resistor on the input and simply connect the device to ground/3.3v and your DI. The MSRP for the device is $20, but discounts are available if you have an account with them. I’m not affiliated with them, other than being a long-time customer for devices such as this. I’ve used dozens of these without any problems.


Thank you!

Have you used with particle photon?

Thank you

Thank you

Just for clarification, when I said

I didn’t imply that the OP’s setup was three-phase, nor does the warning only apply when the respective “home system” uses three-phase. I was refering to the utility grid which is usually three-phase and hence the risk is virtually omnipresent even for single-phase homes using the utilities “virtual neutral point”.


@jonamleonel, I add IoT functionality to a lot of different types of large equipment.
My Personal Rule is to never use the existing equipment/controls/sensors for the IoT Service.
That is both for Safety and Liability.

For instance:

  • I’ll add a pressure sensor instead of using an existing sensor
  • I’ll add Split Core CT’s to measure AMPS, instead of using the outputs in a control panel
  • I’ll use an Opto-Isolator to read digital outputs from a panel, instead of directly measuring with Electron.
  • etc, etc…

My goal is to eliminate any connection that could impact the original system if my IoT equipment experiences a failure. Imagine if I Smash the Photon/Electron with a Hammer…I will never be able to predict what state each pin will end up at. So I try not to install anything that could impact the control scheme no matter how exotic the failure mode is for the IoT equipment I’m adding.

Note: I’m not implying that your proposed plan is wrong, I just wanted to share with you my general thoughts.

Having said that, +1 to the recommendations you’ve already received (CT’s or a Current Switch).


Many, many times. I’ve used them both with Photons and Electrons as well as micro-controllers of different persuasions. They’re very reliable and keep you totally isolated from the circuit being monitored. Be sure to select the one with the right specs for the circuit you’re monitoring. The ones I recommended are split-core, so installation is a snap…literally! :wink:

do you use pull up resistors with capacitor? what configuration and values do you use?

Excelent answer and opinion. Thank you so much, I am learning a lot

I typically use precision 10K (1% or better) resistors and a 100nF capacitor, connected in parallel from the input to ground (pulldown). I like using the precision resistors as a standard on my boards in this configuration, as I use it also on ports that support both digital and analog so I can use them for 10K NTC thermistor inputs as well as digital inputs. I think this is simply a preference thing and my library for thermistors assumes the resistors are in pulldown configurations. I also like seeing the input ON when the contact is closed for digital inputs.

I apologize for the slow response…busy couple of days.

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