Photon not draw power until “prompted”

Hello,

I am super new to Particle and embedded in general, so be gentle :wink:

I took an basic embedded class last semester and my project was to make an Alexa controlled smart window blinds. Basically I prompt Alexa and Alexa calls the particle function on the photon which then runs the motor connected to the window blinds. Since the class I cut out the Atmega (and a few others the class required) and I’m using a Photon, a stepper motor, the stepper driver, and a 12v to 5v linear voltage regulator.

My question is, is there a way to get the Photon to not continuously draw power until it’s prompted by Alexa? I saw in the documentation that turning off the WiFi is the best bet because it draws the most power. However, I just can’t get it to work. What I’ve been trying…after the motor operations I’ve tried turning the WiFi.off/.disconnect, then in my setup, before initializing the Particle.function, I try to reconnect using WiFi.on/connect (meaning I’ve tried both) and it just doesn’t do anything. It won’t actually try to reconnect the WiFi when the particle function is prompted after the WiFi has been turned off or disconnected. I’m not sure what I’m doing wrong. I’ve been experimenting with stuff from this post…

Any help or suggestions is greatly appreciated!

Practically, No. You need to have WiFi on in order to listen for events coming from Alexa. If you disable the WiFi or go to sleep, then you won’t be able to hear the calls or webhooks coming from Alexa. The photon only draws something like 80mA when not doing anything… is that so much that you need power savings? If you are running on battery, that’s a different issue. I think the Electron has a “wake on cellular” mode but I’m not too familiar with it and I don’t think that exists on the Photon at all.

What is your total current draw when not doing anything? Are your peripherals drawing power along side the Photon? If yes, then you might be able to reduce the draw of those peripherals by disabling them.

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Assuming you’re calling this Particle.function() over the internet (which is what it does), try thinking the above quote through thoroughly?

As an experiment, set your phone to airplane mode, then try calling it. Does it ring?

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Yeah, I’m a moron! haha. I must have been very tired last night, I’m not sure why I didn’t think about that. Its the exact purpose of my use case to connect through a wifi webhook! Dang, nothing like being an idiot, in writing, in public.

Anyways, thanks for the responses @ninjatill and @Moors7!

@ninjatill, I would like to connect it to a battery if possible. Right now I’m using a 12v wall plug. The thing that’s been “concerning” me is the linear voltage regulator gets super hot, and if plugged into the wall it will always be that hot because the photon is continuously drawing power.

My options at this point are get a heat sink…or I was thinking, I have a Photon power shield with a 3.v lipo batter, I could use that for the photon and get a battery pack for the motor itself. The battery pack for the motor will probably keep a charge for a while as its only used for seconds at a time a few times a day. I’m not sure how long the lipo battery typically lasts though, any thoughts?

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I would say the excessive heat is not because the Photon is drawing power but rather because of the large voltage difference between the supply (12v) and regulator output (3.3v). There is always loss in that step-down which is dissipated as heat. You could try a lower voltage source such as a phone charger (5v). Or, use an intermediate voltage regulator that doesn’t step down as far (i.e. 12V to 5V)… You might still need a heatsink but now you have a discrete component to attach it to instead of the Photon PCB).

As for the battery, the Photon doesn’t have a LiPo connector for a reason… It just wasn’t meant for super-long battery operation as, say, the Electron or Boron. If you want to use a battery, then you have to estimate the average current draw of your project over a period of time. (I.e. 100mA over 24 hours). Then you know you would need a 2400mAh battery to last 1 day before recharging. Even with that crude guesstimate you can see you need a rather large battery to last a non-annoying amount of time between recharging. Your application seems better suited for a wall plug kind of power supply.

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That all makes a lot of sense and thank you for the great suggestions! Maybe I should switch to an Electron and make some sort of remote control