Power Bank Battery Sleep

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skr0d
 
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Power Bank Battery Sleep

Post by skr0d »

I just picked up the Power Bank http://www.adafruit.com/products/1565 and intended to use it on my blinky Halloween projects, since it provides a lot of juice for my hungry Neo Pixels. My first test with a 5v Trinket and 8 Neo Pixels went very well. The battery will long outlast Trick-or-Treating. For fun, I was also going to make another quick project with a 3v Trinket and a capacitative touch sensor. For the most part, this circuit is very very low power. So low, in fact, that the Power Bank doesn't even notice that I am drawing power, so it goes to sleep. :(

I guess that says a lot for how efficient the 3v trinket really is!!

But, I wonder if there is a way to disable the power sensing feature on the Power Bank. Probably not, since the case looks sealed. But I thought I might share this with everyone. In this case, I'll just switch to AA batteries. No worry that they will run out before the candy is gone.

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adafruit_support_mike
 
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Re: Power Bank Battery Sleep

Post by adafruit_support_mike »

Thanks for letting us know about that.

You're right that it would probably take a hacksaw to reach the bits that control the sleep behavior. The hardware connections seem to be minimal.

Try hooking an LED between the USB+ and GND pins as a dummy load. A 150 ohm resistor should give you about 25mA of continuous draw, which will probably be enough to keep the power pack awake. If you need more draw, non-LED Christmas lights make good dummy loads and cost about a penny each.

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skr0d
 
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Re: Power Bank Battery Sleep

Post by skr0d »

I didn't have any 150 ohm resisters sitting around, so I figured I'd start with a 100 ohm. According to my calculations, on a 5VDC circuit with a 2.5 Volt LED, I get 25 mA with a 100 ohm resister. That seems to match what you were saying. With this configuration, the power supply still goes to sleep. Since I don't have anything smaller than a 100 ohm resister, I just started stacking them in parallel to reduce the resistance, and went all the way down to 25 ohms (4 resisters in parallel), sucking 100 mA, and the thing still went to sleep.

Do you have any spec sheets on the product that might suggest the minimum amount of current before it sleeps? Obviously, powering a Raspberry Pi or an Arduino Uno should draw enough on its own... Or, will it.

I plugged in an Arduino Uno, with one LED (in addition to the one on the board) and it went to sleep, just like it did with the trinkets.

If I plug in a seven-segment LED backpack and light up two digits, it draws enough power to stay awake. Now, because I am curious, I'm going to get out my ammeter and see if I can tell what its lower limit for sleep actually is.

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skr0d
 
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Re: Power Bank Battery Sleep

Post by skr0d »

I just realized that I can't measure it unless I hack apart one of my precious UDB cables. But, maybe its worth it, FOR SCIENCE!!!

BTW, when I turn off the the LED segments, but leave the backpack on, it stays awake. And If I light up a single segment (I used the number 5) it also stays lit.

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adafruit_support_mike
 
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Re: Power Bank Battery Sleep

Post by adafruit_support_mike »

You can have the best of both worlds with one of these: http://www.adafruit.com/products/1549 ;-)

WRT the above, 100 ohm resistors are fine, and the real win is that you calculated the expected current before plugging things together and seeing where the smoke comes out.

A tip for when you start buying resistors ($4/200 at Mouser): circuit designers use what's called the 'E' series to choose values. The E6 series is { 10, 15, 22, 33, 47, 68 } and the E12 series is { 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 }. Each number in the E6 series is about 50% larger than the previous one, and each number in the E12 series is about 20% larger than the previous one.

I don't think we have any datasheets that show the sleep current, but I'll ask around.

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djix123
 
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Re: Power Bank Battery Sleep

Post by djix123 »

Would it also be possible to find out how long the battery pack takes before it sleeps when the current drops below the threshold? That would also be very useful.

Thanks, in advance,

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umop_apisdn
 
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Re: Power Bank Battery Sleep

Post by umop_apisdn »

It looks like I'm having a similar problem. I have charged the new Power Bank for several hours, but when I try to use it, it shuts down after about 22 seconds. According to a USB meter that can measure the voltage and current being drawn by my project, I'm drawing about 120 ma at just over 5 volts. I've tried several devices as loads and they all shut down about 22 seconds after I plug them in. Does this sound like the "sleep" problem, or perhaps a defective Power Bank?

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skr0d
 
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Re: Power Bank Battery Sleep

Post by skr0d »

I had mine powering an Arduino Duo with 5 led matrix displays, and it lasted all the way through Halloween! It even had power to spare at the end. The built-in flashlight came in handy as I dismantled my display after dark.

I think its a low-current-draw sleep cycle. If I'm pulling enough, it stays on. The big questions is, "What is that threshold?"

I don't have a nifty device to measure load on my USB, but it seems like you do, Mr. Upside-Down! Could you do some measurements? Add some load, measure it, and see if it goes to sleep. Share it with the rest of us so we can all benefit!!

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umop_apisdn
 
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Re: Power Bank Battery Sleep

Post by umop_apisdn »

SKROD or Adafruit,
Did you have to add a resistor to keep the Power Bank on? I'm trying to use the Power Bank to power a project using an Arduino MEGA, an Ultimate GPS breakout module and a graphic LCD device. The Power Bank is providing power through the MEGA's USB port. The project draws around 120 ma during use. It seems like this should be enough load to prevent the Power Bank from going to sleep, unless the Power Bank I have is defective. The project runs fine off my PC's USB port for power.
But it shuts down after about 22 seconds on the Power Bank. Any suggestions?
John

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skr0d
 
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Re: Power Bank Battery Sleep

Post by skr0d »

My current project has a 5v Trinket at 8MHz (9mA) and 4 NeoPixels that range between 20mA and 60mA depending on the brightness and the color of the light being emitted. My project was used to create a color changing effect in my windows for Halloween, and would randomly flash the NeoPixels at full white a few times to simulate lightning. It worked very well on the PowerBank, and never went to sleep.

If we look at the math, I was probably drawing 89mA at a minimum and 129mA during the lightning sequences. I don't have a way to measure this at the moment, so I'm going with the posted specifications.

I suspect that the random lightning sequence at 120mA was enough to keep my PowerBank awake. I'll try removing a NeoPixel, or maybe 2, and see how long it lasts. Maybe I'll also try reducing the brightness of the lightning sequence, or skip it all together to see if I can make it sleep, and uncover the hidden lower limit to current draw the makes the Power Bank bored and have to go to sleep.

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skr0d
 
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Re: Power Bank Battery Sleep

Post by skr0d »

During some trials today, I have come up with this:

The Power Bank 4400mAh battery will power a 5v Trinket and two Neo Pixels. Anything less, and it goes to sleep after about 20 seconds.

Specifications show the Trinket draws 9mA and the Neo Pixels draw between 20mA and 60mA for a total of 40-120mA together. This shows that 49-129mA is enough to keep the battery from going to sleep.

I've ordered a USB measuring device from Adafruit. When it arrives, I'll put it in-line and see what we get for actual measurements.

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umop_apisdn
 
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Re: Power Bank Battery Sleep

Post by umop_apisdn »

I'm having trouble with the 10,000 mAh Power Bank. Based on your 20 second timeout, it seems like that's the problem I'm having. I haven't seen the Adafruit USB metering yet. I'm using a unit called a "portapow". I've never checked its calibration, but I will.

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adafruit_support_mike
 
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Re: Power Bank Battery Sleep

Post by adafruit_support_mike »

I'll order one and put it on a programmable load to see what I can find out about its sleep limits.

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paulstoffregen
 
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Re: Power Bank Battery Sleep

Post by paulstoffregen »

I've got a similar battery pack. Doing some experiments on it right now. Details here:

http://forum.pjrc.com/threads/24476-Por ... #post37143

TL;DR: a 230 mA load pulsed for 25 ms every second seems to keep it from turning off.

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paulstoffregen
 
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Re: Power Bank Battery Sleep

Post by paulstoffregen »

I built a minimal circuit with 2 transistor, 1 capacitor and 2 resistors that keep the battery pack on, with minimal power drain.

Details here:
http://www.dorkbotpdx.org/blog/paul/battery_pack_load

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