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

It's funny how some people react to using an MCU for a task that can be done with analog. An MCU is one chip which is hard to reduce further. But in reality it is one chip on a *board* that can be wired into the circuit *very easily* to handle two possible power circuits at the same time. A digital solution allows for a *lot* of flexibility in how the circuit alerts the user and how it is bypassed when needed. It is also very easy to update with new functionality.

An MCU solution can be bought off the shelf and inserted into a 12V power splitter which can be bought for $5. Simple, easy and cheap. No proto boards needed. Just a minimal amount of soldering and Bob's your uncle.

Geeze!

I started a design with an LM324 or LM393 and it quickly became too complex, though since I worked eight years at NatSemi, I have some nostalgia for their analog parts.

Here's the deal. An Arduino costs about $11 . The A/D inputs are a good fit for this.

The other items are sense resistors and a Sonalert. Probably also a SPST momentary switch to manually silence the alarm.

Arduino is not always the answer But neither are op amps or comparators.

So to sum up the arduino approach costs 10x the price & does the same job. On which basis you like it. 'Designers' with no engineering sense are not very useful.

NT

sounds like something went wrong with your design.

Nothing is always the answer to anything. That is hardly worth pointing out. Arduino: $11 + other bits LM324: cents.

NT

you can get and arduino nano clone for a dollar or you can just buy the AVR

Except it's not just an LM324. There are a bunch of other bits and pieces.

By the time you deal with all the other pieces, and wire it on a perf board, you're much better off with an Arduino with its A/D, comparator, and I/O. And of course the Arduino board is only so expensive ($11) if you want it fast. You can buy a Nano for about $4 in the U.S., $2 if you want to wait for it to be shipped from China (free shipping).

Especially because an MCU includes analog.

I looked at using comparators or opamps (LM324 or LM393 or LM339). The thing is that it's not just that one part. There was a switch, diodes, resistors, and a flip flop as well.

I think that some people are terrified of having to program an MCU. But the Arduino is pretty trivial to program.

Already has keyless remote for starting.

What would work is a starter relay controlled by Bluetooth.

So, what's wrong with tieing the phone and remote together? Make sure she has to carry both to drive.

...from the guy who hates women (the feeling is mutual, obviously).

The arduino is has a huge factor improvement in effort to make it work. Buy a board, solder it in, write some code, done. How would he get the op amp circuit built and in the car?

I know they make clones that are a fraction of that size. If all you need are the MCU and a couple of resistors, they make "stamp" sized Arduino boards.

As I said, I first considered the op amp or comparator approach. I began to draw the circuit in a schematic capture program. The number of extra components began going up to a level where it became clear that a small micro-controller was more practical. When you can buy an Arduino Nano for $2 (from China), or $4 (from the U.S.) starting to hand wire a single perf board circuit is practical only if time has no value.

Dumb idea. She's not going to walk around with a keyless remote attached to her phone.

You just don't have the right keyless remote. If i build the remote, it would be a small flob that plug into the phone's usb port. The existing one are too big for no reason.

I don't see anyone holding you back... I'm just sayin'

Only time is holding me back. I got too many ideas. Following the foot-steps of Tesla Motor, Faraday Future. My Maxwell 2020 (or perhaps 2030) will be GPS and cell connected. When my phone is inside, it will start. No need for another radio either.

yes, resistors & 2 capacitors.

NT