v3 - Atrix is DIScharging, not charging?

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adafruit_support_bill
 
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Re: v3 - Atrix is DIScharging, not charging?

Post by adafruit_support_bill »

The IC will shut itself down if it overheats. This usually happens if the phone it pulling more than 500mA. According to the USB charging standard, the phone should not try to pull more than 500mA unless the charger identifies itself as a fast charger. If, as another user reported, the Atrix is pulling more than that, it would explain the overheating. Also in this case, using batteries with higher current capacity will only enable it to overheat faster.

If you can't get it to work with your phone, we can arrange for a refund. Just contact [email protected] with a link to this thread.

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

Ah. Well that explains it then. I've measured the current draw from the Atrix using its supplied 1A charger, its 854mA. That's more than 500mA. And it definitely overheated - the foam pad I used to place it in the tin melted onto the PCB board. So there's no way to get it working with my phone then? Can't just insert some sort of high-wattage current-limiting resistor in there? Thanks for helping me with all this, by the way, and thank you very much for the offer of a refund, I'll check that out if I can't get this working.

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

So if I'm to understand correctly, its the IC, not the batteries, that's the problem. The batteries appear to charge and discharge fine still, they weren't damaged at all. So maybe there is some IC DC-DC converter out there that is capable of up to 1A? Or would that damage the batteries and other components in there (I notice, for example, that the electrolytics are rated to 105°c)

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

Nevermind, according to Digikey, you picked the highest current through-hole mount 5v output IC there is:

http://www.digikey.com/scripts/dksearch ... ageSize=25

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

So I've had some time to take a closer look at what is going on here. The Atrix has three charging modes: 1) Fast AC, where it will try to draw as much current as possible, because it thinks it is plugged into a wall charger. 2) Fast USB, where it will try to draw 400mA if the computer's USB port allows it. And 3) Slow USB, where it will charge at whatever the computer does allow it to charge at.

I also learned how to measure current with a DMM, and I spliced open a USB cable so I could measure it. When the Atrix is plugged into its own supplied 0.8A wall charger, it draws between 450 and 800mA, depending on what you are doing on the phone. When it is plugged into MY computer's USB port, it draws exactly 400mA, no matter what you are doing on the phone. And when I plug it into the MintyBoost, it will start out drawing between 300mA and 450mA, and it charges normally at that rate, and the mintyboost only gets kinda warm. But it will slowly climb up, to max out at 560mA, and thats when the mintyboost case gets hot, and the inductor starts resonating and making that squeaky noise, and the little foam pads start melting onto the solder joints on the board. This is (pretty close to) the 600mA limit of the DC-DC boost converter in the mintyboost, because even if I turn on the phone's flash light AND do a CPU-intensive test, it won't go above 560mA.

I don't know why it is slowly climbing like this, perhaps because the Atrix is actually always trying to draw 800mA (its max), but the Mintyboost will only supply it 300mA at first, until after about 15 minutes it "warms up", and then it tries to supply its max 560mA?

Either way, is there any way to kind of "simulate" a computer USB port, to force the Atrix to limit itself at 400mA?

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Re: v3 - Atrix is DIScharging, not charging?

Post by adafruit_support_bill »

The USB standard for a dedicated charging port has D+ and D- shorted. However, the standard does not limit the current that can be drawn from such a port. Apple chargers signal current capability by voltage. 2v on D+ and D- indicate that the device should not try to draw more than the standard 500mA limit. Other voltages signal higher capacities.

The minty emulates the Apple standard with the resistor network. With D+ and D- shorted, it emulates the newer USB dedicated charger standard.

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

What if I were to replace the batteries with a solar panel that generated <500mA, that would prevent the device from being able to draw >500ma, right? Although I would only be able to use it in the sun, and it would probably turn on and off a lot if it wasn't able to produce the minimum voltage.

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Re: v3 - Atrix is DIScharging, not charging?

Post by adafruit_support_bill »

Your basic idea is valid - limit the current. But solar panels have their own set of problems. When the current draw increases, the voltage tends to collapse. See here for more details: http://learn.adafruit.com/usb-dc-and-so ... sign-notes

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

I'm sorry, I've been building electronics for 10 years, and I still basic electricity confusing. But don't you mean when the current production increases, the voltage tends to collapse? Because in my case, the Atrix will always be trying to draw 800mA, so the panels will be trying to supply their maximum current (relative to the sun) at all times.

We actually have our entire house roof covered in 10kW of solar panels, so I know a little bit about MPPT. But the way I always understood it, was that the DC current coming out of the panels was entirely proportional to the amount of sun hitting them, but the DC voltage coming from the panels was controlled by the microinverter, that decided what the best voltage to use for that current is.

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Re: v3 - Atrix is DIScharging, not charging?

Post by adafruit_support_bill »

But don't you mean when the current production increases, the voltage tends to collapse?
No. Current draw is determined by the load. If the panel could produce more current, the voltage would not collapse.

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

Okay, thanks for all your help and info! I'll give it a shot, see if I can get it to work at all. I've got a few 3v solar panels from some old outdoor night lights; if I run enough of them in parallel, I might be able to get some decent current out of them. But I think I'd have to design some way of delaying the MintyBoost from turning on, for at least a second or two, so that if/when the input reaches threshold voltage, it doesn't cycle on/off a hundred times in one second. I'm sure some kind of capacitor+transistor-based simple circuit would do the job.

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

Okay, well I tried just one tiny little 2" square panel, and while it generates 3.3v in the bright sun just fine, I was only able to get 7mA out of the mintyboost, lol thats not gonna be enough! Looks like I'd need at least 10 or 20 of these things. Maybe using nothing but the solar outdoor lights was a little ambitious...

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Re: v3 - Atrix is DIScharging, not charging?

Post by moeburn »

Me again.

I noticed that there were higher-current boost converters if you get them in surface-mount form. Well I have some left-over SMT-DIP adapters, and I've had success soldering 8 pin SO8 SMTs on them before...

Could I pop this one in the circuit without any changes?

http://cds.linear.com/docs/en/datasheet/1306f.pdf

It's made by the same manufacturer, and its the same family of ICs. The MintyBoost v3 uses an LT1302. This is an LT1306, it looks like the only differences are the maximum current, and the switching frequency is about 100khz faster.

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Re: v3 - Atrix is DIScharging, not charging?

Post by adafruit_support_bill »

and the switching frequency is about 100khz faster.
You would probably need to re-engineer the LC part of the circuit and tune it for the higher frequency.

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