Hello all,

Im relatively new to the electronics scene and i hope i'm posting in the correct place, apologies if not. I've embarked on, for me at least, a pretty ambitious project. The overall idea was to create a multi mobile device charging unit which sat within a unique housing. Straightforward until my friend suggested i put a speaker system in and have it as a phone dock also, which is a cool idea so i have to run with it.

So my actual question: Is there a way i can create this in such a way that the unit can be plugged into a standard wall outlet and charge both a cell inside the unit and power the unit itself and then when taken from the main supply the battery kicks in? I've been looking at the circuit boards on an emergency light but the one i had to test was only outputting 3v DC and this wouldn't be enough to power the speaker system as well as up to 4 mobile devices charging.

I found this website and thought perhaps you guys could help?

 

The minimum voltage requirements for your mobile device would be a 5v power supply.
So you have to tell if you are ready to build from the scratch or just put together units to make it work.
What are the circuit elements you have on ground if any what are the specifications like the battery cell so we know if it's a step up or step down DC-DC converter

 

The minimum voltage requirements for your mobile device would be a 5v power supply.
So you have to tell if you are ready to build from the scratch or just put together units to make it work.
What are the circuit elements you have on ground if any what are the specifications like the battery cell so we know if it's a step up or step down DC-DC converter

Hi, Thanks for replying, at the moment i have nothing, i had an emergency light on had just to test, the battery cell was a 3.6v 700mha NiMH cell. At the moment all i have is the housing as I'm repurposing an old item, but before I spent loads of money on stuff thatdidn'tt work thought i'd ask the experts.

Initially i thought about a powered USB hub with a Powerbank as the battery but was concerned about overcharging especially when the hope is to use it as my daily on my night stand charger. I hope im answering your question correctly.

 

You mention a "speaker system" without any details about what power it is designed to use. So it could be anything from a wimpy amplifier running on 3 "AA" batteries up to a car radio with amplifier delivering a hundred watts of audio each channel. the power requirements are quite different. Many of the folks who post answers, myself included, are very poor mind-readers, especially at a distance. Thus we need facts to figure out answers. Charging mobile devices via USB cords from a 5 volt supply is simple, adding a connection to charge a battery for an emergency light is not a big challenge unless it has to be free. Powering a speaker system of some kind will require a different power source, or at least a different output from the one supply. But all of it is quite do-able,and the circuits to do it already exist someplace.

 

Requirements
-usb hub
-battery cells 3.7v
-buck converter unit (3.7v to 5v @ 1A)
You can decide to build the buck converter on your own or buy from local electronics store
Running the speaker on this is not a good idea so you need follow up what @misterbill said by employing a seperate power supply..

 

There are a whole lot of power supplies that will provide 5 volts regulated at several amps and also deliver 12 volts at an amp or more. They are also available used surplus and from a number of liquidators, and most of them are rated for constant service, so they should last a long time. The added advantage as that many of them are in a neat package.

 

Hi all, thank you for all the advice so far, I’ll start reading up on the above. The speaker system is as yet TBC as I wanted to see what my options were with regards to the battery back up.

I’m hoping I can get a cheap iPhone dock off eBay or similar and then when I have this I’ll report back with power supply needed. Thank you again for all the help so far. I’m sorry I’m not very good at explaining myself, so thank you for being polite and not just dismissing me. Very cool of you!

 

Sharing knowledge and insight is what this website is about, and I am happy to share. And some of the questions are very interesting indeed.

 

Hi guys, update, I've decided to try and make things a little easier for myself. Firstly thank you for the advice, I took it on board and did a little research.

I've decided to have 2 emergency light boards (sorry I don't know the technical name). I've done a VERY basic sketch of the design and I was just wondering whether I have done this right, I'll try and use the right vernacular when i describe it
So I've got a single kettle lead AC port leading to two Emergency lighting boards (Again sorry i don't know the correct term). Each board is connected to a single 3.7v Ni-Cad Cell, then each of these boards is attached to a buck converter (as suggested by falsade47, thank you) which steps it up to a 5v connection.
The left side then connects to the USB hub which will allow the charging of devices. On the right it goes to a Bluetooth amp which will have either 2 25w or 50w speakers.

Hopefully ive explained myself enough for someone to help. One of the main questions i have is although the USB hub will require 5v to power it, will 5v be enough to run all the ports if 4 or more devices are connected?

 

will 5v be enough to run all the ports if 4 or more devices are connected?

5v would be enough since they are all connected in parallel but the current would be shared according to each load connected respectively. So if your buck converter outputs 5v @ 2A, all usb ports would hold a 5v pd across them and if you have all 5 ports in use, that means the current would be shared by 5 dependent on the device connected.

 

If at all you have 5 ports on the hub.
You need a 5V regulated supply capable of supplying 5A connected to each and every usb port.
That means that if only one port is used you could draw 5A from it

If you want to limit the current to a maximum of 1A from any single port then you could use five separate current limited regultaors, for instance 7805.

 

If at all you have 5 ports on the hub.
You need a 5V regulated supply capable of supplying 5A connected to each and every usb port.
That means that if only one port is used you could draw 5A from it

If you want to limit the current to a maximum of 1A from any single port then you could use five separate current limited regultaors, for instance 7805.

So in if i wanted to charge 5 devices at 5v i would need 5 wires from the buck converter to every USB port OR would i need 5 completely separate Power supplies?

Sorry this may be a stupid questions.