Sense When No Phone is Plugged Into a USB Charger In Vehicle

Periodically, including today, my wife heads off to work without her phones, and when she gets to work she either has to come back home, about nine miles in heavy traffic, or if I haven't left yet I detour on my way to work to deliver them, or my son happens to be home from college (like today) he delivers them.

What I want to do is to have a device that sounds an alarm when the car is started (USB charging port turns on) but no device is plugged in.

So I want to detect the current flow from the USB +5 to the phone and if there is no flow, sound the alarm. There is always some flow upon power-up, even if the phone is charged, then it stops if the phone is already topped off.

There are current shunt monitors, i.e. the TI INA233 which would probably work, but does anyone have a better idea.

I'm thinking a using an Arduino Uno (%V analog inputs) with a shunt resistor between two analog pins, reading the values of each analog pin, and activating a speaker if the analog values are the same (no current flow) so she'd have to plug in the phone to stop the speaker. Plenty of analog pins so I could do one with a Lightning cable for her Android phone (personal) and one for her company phone (iPhone).

If I wanted to get really fancy I could add a Wave Shield and output some speech.

Reply to
sms
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Why not detect the presence of the phone using bluetooth? Then it does not have to be in the charger and you don't need to fiddle with hardware monitoring of current etc.

Reply to
Rob

It also doesn't have to be in the car when you leave and might only sound an alarm after you have pulled out of the parking area.

Personally I find Bluetooth to be a bit of a PITA. It is not uncommon to find the paring doesn't happen when I first turn on my headphones or sometimes at all and I have to manually connect. I would think this would need to be more reliable than that.

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Rick C
Reply to
rickman

That was my first thought, but I could not figure out a way to do that.

Reply to
sms

Tell her to pay more attention. You'd imagine having to trek nine miles back after forgetting it a couple times should be an effective reminder to double-check.

If she insists on an engineering solution ask her what a job like that would pay.

Reply to
bitrex

I looked into an Android board with build in Bluetooth (Feather BLE) but the issue is that you have to detect the lack of a Bluetooth connection, and that's not trivial, since pairing is hit or miss.

I don't want to make this project a career. An Arduino can directly drive a Sonalert, and all I'll need a shunt resistor that can handle the current if the battery is charging. I'd probably only do one power connection since the iPhone is the important phone, plus she would never forget one phone but not the other.

The other problem is that some days she bicycles to work. I have no solution for that. A Bluetooth enabled bicycle lock would work if the bicycle were parked outside, but it's not.

Reply to
sms

I believe he referred to her as "wife". I expect the pay was negotiated long ago.

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Rick C
Reply to
rickman

Maybe this is her way of indicating she needs a car with Bluetooth for hands free phone usage?

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Rick C
Reply to
rickman

Ah. I didn't realize it was a breach of contract to tell one's wife "no" sometimes. It sounds like a bad deal. Probably part of why I'm not married

Reply to
bitrex

What's the problem with a sense resistor & opamp/comparator then an LED or beep circuit?

NT

Reply to
tabbypurr

INA219, high side dc current (and voltage) sensor, available on a breakout board from Adafruit for around $10, and they have Arduino libraries to support it as well. Much cheaper unless you can get TI to send you the INA233 eval board for free (and even then, the Adafruit INA219 board is a lot smaller).

Sense current flowing thru the port, as with the INA233. Another thing to look at would be sensing voltages on the USB data pins. They probably have resistor networks on them (commonly used to signal how much charging current is supported by the port), and will/might shift with a device plugged in.

Reply to
artie

Reply to
Don Y

It's not that you can't say "no"... you just want to choose your battles. How often do you tell a customer "no"? You choose those times only after careful consideration. SMS is doing his due diligence.

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Rick C
Reply to
rickman

How about a NO-TECH solution called a reminder sign on the dashboard.

*** Do you have your phone with you ? ***

No need for electronics with an ever present nagging sign.

Regards.

Reply to
alan.yeager.2013

Saying "no" to taking out the garbage on the regular is probably a bad idea.

He's talking about building an automotive cell phone connectivity detector out of a INA233 current shunt monitor as a "honey-do" project!!111

Engineers... /roll eyes

Reply to
bitrex

As Red Green says, "If women don't find you handsome, they should at least find you handy!"

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Rick C
Reply to
rickman

I sense a youngster. How does that make more sense than a 1 cent resistor & LM324 opamp?

NT

Reply to
tabbypurr

Maybe you should explain it to us like we are six year olds?

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Rick C
Reply to
rickman

Indeed!

There is no guarantee that she would plug the phone into the charger is there?

A small sign on the ignition lock would be the best place.

However engineers like electronic solutions so I recommend an illuminated LCD sign showing "Do you have your phone?" by the ignition lock. Perhaps a buzzer or small audio voice device saying "Do you have your phone?" too?

That is nice - a visual, audio reminder along with the other reminders that cars like to present us with.

John ;-#)#

Reply to
John Robertson

ar

if

or & LM324 opamp?

LM324 input goes down to ground. So put an R in the -out line and use your

1/4 324 to see if current is flowing, with the other input terminal driven by a resistor divider. That stage output goes to the next through a diode. Stages 2&3 generate bleeps. When current flows, diode conducts so the bleep er is kept silent. Add an LED and a STFU switch too. Keep piezo drive volta ge low, you don't want it anoying. Easiest done by making the pulses narrow & driving it through a resistor. I have no idea why anyone would use a com puter to do that.

NT

Reply to
tabbypurr

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