DIY Car Tracker Power

Thread Starter

Big Dingus

Joined Oct 22, 2018
32
Hi folks.
I was looking to fit a tracker to my car. When I looked into it I found out just how expensive these companies are.
So I came up with my own idea. I got hold of an now unused iPhone hidden in the car, with the intention of using the app find my phone that is perfect for position fixing. A data only sim is very cheap. Much cheaper than a tracking company.

So the issue I have is power.
Getting a constant power is no problem. However, should the car battery be removed then everything may be powered from the iPhone battery. I thought to fit a diode on the + side. Can anyone suggest what size I should fit to achieve this?
Can anyone think of a problem with this?
 

MrSoftware

Joined Oct 29, 2013
2,188
If you use the standard USB port to power the phone, then there's no way for the power to flow back the other way, nothing for you to do. Just get an off the shelf 12v to USB adapter to power the phone.
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
32
I've sourced a supply from the feed to the ignition. I'll strip the iPhone cable and just solder it inside some shrink. That way it's hidden from anyone looking for a tracker. Mount the iPhone as high in the dash as possible.
 

DC_Kid

Joined Feb 25, 2008
1,072
I am not even sure you could power anything from the + wire that goes into iPhone port. The phone has its own internal charging system to accommodate the lithium battery it uses. The charging system is likely one way only, and that's in.

1) A LittleFuse resettable PTC fuses are good items in this scenario.
2) A linear LM7805 regulator is all you need with PTC fuse, wired direct to battery.

7805 will waste power all the time, but the car battery is many magnitudes bigger and will survive when car is not running.

If you wanted to get more fancy, you can use programmed wake-up IC (Adafruit or other) which powers on from sleep every so often, stay awake for a period of time, and then go back to sleep. This could control say a FET (silicon switch) which gives power to the phone to charge up. This way the 7805 is not always wasting power.

Also to note, USB charges likely have a filtering cap or two to take out any noise that alternators make, etc. So you could use wakeup IC and FET to switch power on to a USB charger, etc.
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
32
DC you can use the + on the ignition. I've used it many times for other things. Hands free, internal cameras and others. Obviously you need an inline fuse. The reason you don't use a wire direct from the battery is stealth. Car choppers look for these 1st.
The iPhone uses about 0.1 watt an hour so leaving it on 24/7 is not a problem.
The phone battery becomes a backup only.
The Eskimo sounds good, I'll have a look.
As for smoothing, I don't think it would be a problem.
 

DC_Kid

Joined Feb 25, 2008
1,072
Any location on a car where you can get +12v all the time is the "battery". Whether it be from fuse box as a connector labeled "ignition" or some place else. But "ignition" usually means +12v when you turn the ignition to a 'on' or 'run' position. Fuse boxes usually say "bat" or "batt" if it a source of constant 12v.
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
32
Yes DC. It’s done in many different ways. Sometimes it’s just a plain heavy duty switch, found in old trucks, and some times the switch powers relays.
If I remember correctly. The only thing that is powered directly in a car, was the starter motor. At least is was once.
There are a number of things in a vehicle that is always on (receiving power). ie The alarm. The clock. The entry lights. The radio etc etc A taxi has even more powered on.
Getting power is not a problem, but as I’m not sure of the iPhone I was wanting ‘belts and braces’.

I’ll post back and let all know how it goes. Might give everyone a cheap tracker and put the price of second hand phones up.
 

DC_Kid

Joined Feb 25, 2008
1,072
Many cars had +12v on the cigarette lighter all the time.
There was also a few places in fuse box that had a +12v fuse location.

These days with newer cars, it's hard to find a location that is +12v when the ignition is on.

Unless you have an IC that can sleep in uA range, almost anything connected to +batt will be drawing some ~mA when the car is off.

I have recently added a cooling fan to the back of my alternator in a SUV, it was just getting to hot when the vehicle was turned off, in close proximity to exhaust header. The heat would eventually cause the regulator to burn out. I created a crude timer ckt using one 8pin n+p fet, couple resistors, capacitor. When the vehicle is turned off the fan runs for 8 minutes and then the driving fet stops conducting and the fan turns off.

You could do something similar. When the car is running you give phone power, when car turns off the power remains for a period of time and then turns off. I suspect overnight is when the vehicle is less used, so maybe you keep power on for ~4hrs and then let the phone run on its own batt for a bit.

You'll obviously have the scenario of car being off for a long time, long enough for phone batt to die and phone turns off. But, in that scenario tracking it would likely not be fruitful.
 
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Thread Starter

Big Dingus

Joined Oct 22, 2018
32
Your solution for your setup sounds spot on.
Your correct about my car sitting. It can sit for a month or more. However at a drain of 0.1 the phone would have little impact. Especially as it's a heavy duty one.
 

DC_Kid

Joined Feb 25, 2008
1,072
DC you can use the + on the ignition. I've used it many times for other things. Hands free, internal cameras and others. Obviously you need an inline fuse. The reason you don't use a wire direct from the battery is stealth. Car choppers look for these 1st.
The iPhone uses about 0.1 watt an hour so leaving it on 24/7 is not a problem.
The phone battery becomes a backup only.
The Eskimo sounds good, I'll have a look.
As for smoothing, I don't think it would be a problem.
But 0.1watt (100mW) does not include the waste that is in the charger unit, which is typically from a USB port that likely uses linear device. You might find that the USB charger units that run from cigarette socket actually are wasting more than what the phone is taking. Worth checking out.
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
32
Again DC thanks.
99% of car USB sockets power off with the ignition. After you posted I checked mine. Mine definitely powers down.
 

MisterBill2

Joined Jan 23, 2018
18,176
A second 12 volt battery, a smaller gell cell, would allow a week or more of operation after the vehicle battery was removed, and it could be connected in an "always charging" mode to have a constant very low charge from the mail 12 volt system. Then the biggest chalenge will be hiding the battery. and phone.
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
32
Bill. I once did that as a starter backup. Where I live the temp can drop very low. The spare was always fully charged in reserve. Was actually thinking of doing that again for my golf cart that I keep in the car.
Another story.
 

MisterBill2

Joined Jan 23, 2018
18,176
Bill. I once did that as a starter backup. Where I live the temp can drop very low. The spare was always fully charged in reserve. Was actually thinking of doing that again for my golf cart that I keep in the car.
Another story.
There you go!! Hide the tracker in the golf cart and have a connection to trickle charge that battery. Then just chain the cart to the car to slow down any effort to remove it..
 
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