Powering USB device with off the shelf battery

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Old 11-05-18, 07:41 AM
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Powering USB device with off the shelf battery

Hi All,

Hopefully this is the right place to post this question. I purchased a very simple USB LED light circuit with a capacitive touch switch. You basically plug it into any USB socket that has power and use the capacitive switch to turn on the one LED. Here is a link to the product page:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

My question is if I could buy off the shelf button batteries or maybe even a MN21/23 type batter to run this as a stand alone device without USB power. I'm 3D printing a housing for it to mount for a specific purpose and I don't have USB power available. The complication is that space is tight, so I just can't use a USB power bank. The details on the LED light are sparse, but I assume it falls within the limits of USB 1.0 at minimum (100mA / 5V / 0.50W). As you might be able to tell, I have almost no background in electrical engineering, so this might be a very simple question.
 
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Old 11-05-18, 12:12 PM
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Welcome to the forums.

I'm a little confused here. It says in the info perfect for a keychain. If it doesn't have a self contained battery on board..... how is that perfect ? Are you supposed to carry a USB supply around with it too ? Weird !

3, Working current: 80-100Ma, power: 0.5 W.
So you need a 5v source to supply that. It may even run on a standard lithium type battery like a CR-123 which is 3vdc. The A23 is a 12v battery.
 
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Old 11-05-18, 01:04 PM
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It is hard to suggest a solution without knowing exactly how it will be used.
It might run with 4.5V as well, which will be 3 1.5V cells. Depending on the space you have you can use 3 small coin cell batteries in series or AAA if you have enough space.
Smaller the battery, less power it can produce.

You could also go for 4 Ni-Mh batteries, which will add up to 4.8V.

3V lithium batteries may be too low of voltage. It might work, but probably dim.


If you want to go fancy, you can go for this.
https://www.amazon.com/DROK-Converte...A6SKTENP6ZHFRW

or

https://www.amazon.com/dp/B01FDD3AYQ..._t2_B07D3SQYKJ

you can supply any voltages between 2.6V to 5.5V to output 5V from this.

If you want to hook up Li-Ion battery, there are boards that contains charger circuit as well.
 
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Old 11-13-18, 09:24 AM
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Thanks for the replies, guys. My idea was to hack together pre-made circuits for my desired end result because A) I'm as green as you get with electrical engineering, and B) I suck at soldering. I had printed a 3D housing for a unique flashlight of sorts that will fit on a handheld action cam gimbal. My goal is to keep this as compact as possible. I only need about 100 or so lumens for 20 minute periods, so button batteries just might work. The USB device on that Amazon page is nearly perfect for my purposes in terms of form factor and size, but the question is how to power it from button batteries (if possible). Lambiton: That mobile power supply looks like it would work, but I wonder if I could remove the USB socket to use wires instead.
 
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Old 11-13-18, 12:50 PM
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It's hard to get a feel for how much room you have available for power. Button cells are good but the sockets can get large.

This is a two cell pack with power switch. It takes two 2032 coin cells. It will deliver 6v and be quite effective. You could put a small diode in series with one of the power wires to reduce the voltage to 5.3v which would be fine...... Two cell pack with switch

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Old 11-13-18, 06:42 PM
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I wonder if I could remove the USB socket to use wires instead.
You could. You just need to desolder USB port off.

Rechargeable solution will be much better unless you plan to use your flash light just few times.
 
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Old 11-14-18, 08:42 AM
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"You could put a small diode in series..."

I think he meant to say resistor instead of diode.
 
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Old 11-14-18, 10:52 AM
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No.... a diode. A diode will drop .7v thru itself.
 
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Old 11-15-18, 08:47 AM
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Thanks guys! Looks like some solid advise. I'll give these a go.
 
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Old 11-15-18, 10:11 AM
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I suppose you'd have to use a PN/silicone type diode and not a Shottkey or other type.
 
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Old 11-15-18, 03:04 PM
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Correct. You'd use a generic diode.
 
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