Question about Power Bank - Page 1
Forum section: electronics / beginners

author: desteny
author_rank: Newbie
timestamp: May 24, 2021, 02:44:55 am
content: Hello guys and girls!I just found out this community and i ask your help.I am a hobby photographer, that loves to do Timelapse videos.Most of the time i use DSLR cameras at home, that have some battery dummies connected to them, to power them with the power of home electricity.Unfortunately, the power outages can happen, and lately they have been increasing in quantity.I have came to an idea, to use Power Banks to power my camera. I bought 2 Power banks, each have 3 Outputs - 2 of them are 5V 2.1A and one is 5V 1A.I have found a USB powered Battery dummy, that i can plug into any USB port, and it can be plugged into 2 ports.Unfortunately, Power banks have some smart protection feature, that turns it off, when, i assume very low power is drawn from the battery.When my camera is in IDLE mode, it just waits for intervalometer signal to come and activate it, so when nothing happens, Power bank just shuts off.I have done some experiment:I took usb cable, cut it and connected 3 LEDS to it in parralel. They draw around 50mA of current together and Power bank does not turn off anymore.So far it works for few hours, but i noticed, that one LED gave up and died ( maybe because its rated for up to 3.3V, but i had no other).My question is, can i replace 3 LEDs with resistor? Would it damage my power bank in any way?Is my calculation for Resistor right? R=U/I , 5V/0.05 A= 100 Ohm resistor? Would it heat it up? I dont want to make it dangerous.Sorry, if this post is too long, but i wanted to make it as clear as possible!Thank you very much in advance!

author: ledtester
author_rank: Super Contributor
timestamp: May 24, 2021, 03:15:01 am
content: QuoteYes and it won't harm you power bank. A 1K resistor will draw 5 mA from a 5V source.Maybe see if a 2K resistor will keep your power bank alive -- you'll have more juice for your camera.QuoteDid you use any resistors?

author: DrG
author_rank: Super Contributor
timestamp: May 24, 2021, 03:16:35 am
content: Quote from: desteny on May 24, 2021, 02:44:55 amWe have had at least one thread on power bank stay on circuits. If you check this out, you can see how I did it as well as some citations of how other folks did it -https://www.eevblog.com/forum/projects/(yet-another)-power-bank-stay-on/msg3484944/#msg3484944I think you are on the right track, but rather than draw a fixed amount of minimal current all the time, you can just draw an intermittent current pulse - just what the power bank wants to stay on. In that way, you are not draining the battery anymore than you need to keep it on.Take a read and see if it makes sense to you.

author: desteny
author_rank: Newbie
timestamp: May 24, 2021, 03:24:23 am
content: I did not use resistor, when i used 3 LEDs.I think 1Kohm resistor will be too much, because if current is less than 50mA, it will turn off the power bank.I saw one also try 2 200Ohm resistors in parallel to get rid of too much heat and spread it over both.

author: desteny
author_rank: Newbie
timestamp: May 24, 2021, 03:25:19 am
content: Thank you i will read it!

author: ledtester
author_rank: Super Contributor
timestamp: May 24, 2021, 03:43:53 am
content: Quote from: desteny on May 24, 2021, 03:24:23 amYou need to use a resistor with LEDs or they will burn out.If you ever need to use an LED in the future, there are a bunch of "LED resistor calculators" you can use to figure out what value resistor to use, such as:https://ledcalculator.net/

author: desteny
author_rank: Newbie
timestamp: May 24, 2021, 06:05:39 am
content: Quote from: ledtester on May 24, 2021, 03:43:53 amOkay thank you. So thats why one LEDs already doesnt work.