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Remote controlling my ultra-sonic emitter
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Please be positive and constructive with your questions and comments.

Remote controlling my ultra-sonic emitter

by TitaniumCoder477 on Wed Apr 07, 2021 12:45 pm

Greetings,

I need to control the on/off status of my ultra-sonic emitter device which receives AC 12V 5A.

I'm looking at the following parts list:

1 x Adafruit Power Relay FeatherWing (w/ female header kit)
1 x Assembled Adafruit Feather HUZZAH with ESP8266 With Headers
1 x MPM3610 3.3V Buck Converter Breakout - 21V In 3.3V Out at 1.2A

My first question is how best to power the Huzzah with inline power from the AC 12V 5A? If I use the buck converter on the battery terminal, the buck is providing 3.3V but the battery terminal would be expecting 4.2/3.7V, so I'm not sure if that would work. If I use the buck converter on the USB terminal, the buck is providing 3.3V but the USB terminal would be expecting 5V (which, according to the PDF would be stepped down to 3.3V). And even if that did work, I am not sure how to convert from jumper wire to USB!

After I resolve the above conundrum and successfully provide power to the Huzzah, the rest of my plan involves using the power relay to replace (or tie into) the ultra-sonic emitter's build-in push button switch which is, by default, NC. I will then use MicroPython to create a simple network service that listens for a command on a designed port. Then I will build a simple Node.js web service that provides an API endpoint for a very simple Android app. The end goal is to turn the ultra-sonic emitter on and off from my cell phone.

All of this is a rudimentary roadmap of my first Adafruit project! I would be greatly appreciative of help/direction on my question above and also welcome any recommendations pertaining to my roadmap and end goal.

Thank you in advance!

IMG_20210407_120757b.jpg
Push button and power source
IMG_20210407_120757b.jpg (114.36 KiB) Viewed 35 times

TitaniumCoder477
 
Posts: 2
Joined: Wed Apr 07, 2021 11:30 am

Re: Remote controlling my ultra-sonic emitter

by adafruit_support_mike on Thu Apr 08, 2021 12:31 am

TitaniumCoder477 wrote:If I use the buck converter on the battery terminal, the buck is providing 3.3V but the battery terminal would be expecting 4.2/3.7V, so I'm not sure if that would work.

As long as you don't also connect a LiPo, or a 5V USB cable, that will be fine.

If the board's only power connection is tied to BAT, the only things that will see power are the onboard 3.3V regulator and the output from the LiPo charger. The LiPo charger's output won't do anything unless a 5V USB cable is plugged in, so there's no conflict.

Since you have a 3.3V regulated supply, you could also connect it to the 3Vo pin and bypass the Feather's power circuit completely. it doesn't make much difference though.. connecting to BAT you'll get an extra layer of protection from supply noise and will only lose a few millivolts.

TitaniumCoder477 wrote:After I resolve the above conundrum and successfully provide power to the Huzzah, the rest of my plan involves using the power relay to replace (or tie into) the ultra-sonic emitter's build-in push button switch which is, by default, NC.

Hmm.. that's a bit unusual. Usually a switch that controls power is Normally Open, and closes when you want to turn the device on.

For the application you've described, you might want to look at the Latching Relay FeatherWing:

https://www.adafruit.com/product/2923

It only takes a short pulse of current to flip the relay from one state to another. That way you aren't burning lots of power just to hold the relay closed.

adafruit_support_mike
 
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Re: Remote controlling my ultra-sonic emitter

by TitaniumCoder477 on Thu Apr 08, 2021 10:15 am

Thanks for the excellent feedback! I'll re-examine the push button, but if memory serves me, the moment I plug in AC, the emitter starts emitting and the push button only interrupts it, which would make me think it's NC. But I don't think either type will be a problem for my application. We'll see. I'm a hobby developer, so I am accustomed to "bumps in the road" anyway lol. I have also taken your recommendation on the Latching Relay FeatherWing. I had read the difference between them but somehow choose the opposite of what I had intended! Or, maybe when I decided to power the feather off DC I changed my mind. Either way, this ensures that if I decide to run it off battery in the future I have that option and won't run the risk of draining the battery. Thanks! I have placed my order and am super excited.

TitaniumCoder477
 
Posts: 2
Joined: Wed Apr 07, 2021 11:30 am

Please be positive and constructive with your questions and comments.