Powering my Raspberry Pi
So I want to make my Raspberry Pi go mobile with a simple battery and charger.
Problem is that I need to power more than just the Pi, I basically need 6 different devices, luckily all running at about the same power. 5V, ~1A
Because I don't actually know much about electricity I decided that finding a transformer for 30V-1A, or 5V-6A, was a bad idea because I don't actually know how I'd split the power between the devices correctly
Also I'd need to have a dynamic system because what if I'm only using a couple USBs, or maybe I don't need the screen because I'm using the TV... I need to be able to vary my power usage.
So as a programmer (and not an electrician) I came up with the idea of multiplexing a single power supply across the devices and drew up this schematic:
https://scontent-a.xx.fbcdn.net/hphotos-frc3/1508077_732200780123361_338915380_n.jpg
I have a feeling that this is a stupid idea though and that none of the devices would actually get there required power.
QUESTION IS HERE:
################################################
I want to know how I can power my 6 devices each running at 5V, ~1A (at or less than, no more) from a single power source, either mains or battery.
(I'm sure I can find a way to add a rechargeable power source)
So that's the question, anything after this is just explaining the circuit in the photo I linked, so if you're happy then get answering please XD
################################################
LABELS:
MAINS/BATT: This is my main power source for all the devices (excluding the power board itself which is run under a separate supply)
PWR: Simply a manual switch which toggles whether the devices are drawing power from the mains supply or the battery. This is a double switch which allows the ability of battery charging to be active only when running off mains power, and also feeds to an output connection for external devices to test whether running off mains or battery (just in case it's ever needed)
Supply Test: Can be used by external devices to test which power source there systems are running from.
PWR BATT: The power supply dedicated to the power board itself
(SW)
PI: A push-to-make switch like the power button on any computer, pressing this button will activate power to the PI board, when the PI boots up it'll activate a script that tells the power board to maintain power to the PI even when the switch "PI" is open, boot-time limitations will be taken into account when programming the power boards IC
PI Feedback: This takes a signal from the Pi while ever it is running, when the Pi is shutdown this signal is terminated and the power board can seize providing power for the Pi computer.
(SW)
CHRG: A sliding switch to toggle battery charging, this can only be activated while running from mains power supply due to hardwired limitations (intentional)
(SW)
DISP: A sliding switch to toggle the LCD display, simply an on/off switch. The LCD is not a slave to the Pi device and may be powered without need for the Pi to be powered. This is so the LCD can be detached from the PI and used as a display for another device.
(Transistors)
PI/DISP/CHRG/EXTN (where N is 1-4): The transistors should (I'm not too good with electronics) be acting as electronic switches to control the flow of power from its source (MAINS/BATT) to any device activated by the PIC.
+5V Full Supply: These are shown as screwed terminals but in reality most of them will be hardwired (there are a few limitations to my schematic editor) to there corresponding devices, except for in the cases of some of the EXTernal devices in which case connection point may be provided.
These terminals are the 5V power supply to each device, the supplies are controlled by the PIC and only one can be active at a time, however any active devices are iterated through at roughly 40,000 times per second.
-0V Return: Again these are shown as screwed terminals and may not be true in reality. This is the negative terminal for any devices that have been powered by the "+5V Full Supply", I may add diodes to the return to prevent feedback voltage.
EXT Test Supply: With 4 points at which to add external devices there needs to be a way to test whether any devices are actually connected, These test supplies may be hooked into sensors or micro switches, or simply jumped to there return socket if the external device is guaranteed to be present.
EXT Test Return: The negative terminal for the external testing, any power drawn from "EXT Test Supply" should be returned here for the PIC to detect and activate the power supply to that device.
NOTE, I forgot to add the 10K resistors onto these terminals, each input should have a 10K resistor leading strait back to the negative terminal on the power boards battery. This is to prevent "hanging pins" on the PIC and is required for the safety of the PIC.
Program Download: These 2 terminals connect to my computer so I can load a program onto the PIC so that it knows what to do with all its ins and outs :D
These must also be attached to a ground terminal for safety.
(I think that's everything)
Thanks for anyone who took the time to read that.
And Thanks in advance for anyone willing to educate me, either as to whether this will/won't work and why, and/or what I can do instead to meet my requirements.
Problem is that I need to power more than just the Pi, I basically need 6 different devices, luckily all running at about the same power. 5V, ~1A
Because I don't actually know much about electricity I decided that finding a transformer for 30V-1A, or 5V-6A, was a bad idea because I don't actually know how I'd split the power between the devices correctly
Also I'd need to have a dynamic system because what if I'm only using a couple USBs, or maybe I don't need the screen because I'm using the TV... I need to be able to vary my power usage.
So as a programmer (and not an electrician) I came up with the idea of multiplexing a single power supply across the devices and drew up this schematic:
https://scontent-a.xx.fbcdn.net/hphotos-frc3/1508077_732200780123361_338915380_n.jpg
I have a feeling that this is a stupid idea though and that none of the devices would actually get there required power.
QUESTION IS HERE:
################################################
I want to know how I can power my 6 devices each running at 5V, ~1A (at or less than, no more) from a single power source, either mains or battery.
(I'm sure I can find a way to add a rechargeable power source)
So that's the question, anything after this is just explaining the circuit in the photo I linked, so if you're happy then get answering please XD
################################################
LABELS:
MAINS/BATT: This is my main power source for all the devices (excluding the power board itself which is run under a separate supply)
PWR: Simply a manual switch which toggles whether the devices are drawing power from the mains supply or the battery. This is a double switch which allows the ability of battery charging to be active only when running off mains power, and also feeds to an output connection for external devices to test whether running off mains or battery (just in case it's ever needed)
Supply Test: Can be used by external devices to test which power source there systems are running from.
PWR BATT: The power supply dedicated to the power board itself
(SW)
PI: A push-to-make switch like the power button on any computer, pressing this button will activate power to the PI board, when the PI boots up it'll activate a script that tells the power board to maintain power to the PI even when the switch "PI" is open, boot-time limitations will be taken into account when programming the power boards IC
PI Feedback: This takes a signal from the Pi while ever it is running, when the Pi is shutdown this signal is terminated and the power board can seize providing power for the Pi computer.
(SW)
CHRG: A sliding switch to toggle battery charging, this can only be activated while running from mains power supply due to hardwired limitations (intentional)
(SW)
DISP: A sliding switch to toggle the LCD display, simply an on/off switch. The LCD is not a slave to the Pi device and may be powered without need for the Pi to be powered. This is so the LCD can be detached from the PI and used as a display for another device.
(Transistors)
PI/DISP/CHRG/EXTN (where N is 1-4): The transistors should (I'm not too good with electronics) be acting as electronic switches to control the flow of power from its source (MAINS/BATT) to any device activated by the PIC.
+5V Full Supply: These are shown as screwed terminals but in reality most of them will be hardwired (there are a few limitations to my schematic editor) to there corresponding devices, except for in the cases of some of the EXTernal devices in which case connection point may be provided.
These terminals are the 5V power supply to each device, the supplies are controlled by the PIC and only one can be active at a time, however any active devices are iterated through at roughly 40,000 times per second.
-0V Return: Again these are shown as screwed terminals and may not be true in reality. This is the negative terminal for any devices that have been powered by the "+5V Full Supply", I may add diodes to the return to prevent feedback voltage.
EXT Test Supply: With 4 points at which to add external devices there needs to be a way to test whether any devices are actually connected, These test supplies may be hooked into sensors or micro switches, or simply jumped to there return socket if the external device is guaranteed to be present.
EXT Test Return: The negative terminal for the external testing, any power drawn from "EXT Test Supply" should be returned here for the PIC to detect and activate the power supply to that device.
NOTE, I forgot to add the 10K resistors onto these terminals, each input should have a 10K resistor leading strait back to the negative terminal on the power boards battery. This is to prevent "hanging pins" on the PIC and is required for the safety of the PIC.
Program Download: These 2 terminals connect to my computer so I can load a program onto the PIC so that it knows what to do with all its ins and outs :D
These must also be attached to a ground terminal for safety.
(I think that's everything)
Thanks for anyone who took the time to read that.
And Thanks in advance for anyone willing to educate me, either as to whether this will/won't work and why, and/or what I can do instead to meet my requirements.
Last edited on
Congrats genius...
If you read the title I'm talking about my Raspberry Pi which does not provide full power from the HUB.
The 2 USB ports attached to the Pi aren't driven by the full USB standard due to the limitations of the board so I was going to extend these off into more USBs (because I need more anyway) and provide power to 2 of them, leaving me with 2 fully powered sockets, and 2 still partially powered sockets.
The additional 2 ports aren't for interaction and are just for a charging port for my keyboard and something else.
Also if I was to add my own USB HUB I'd still need to put power into this, hence leaving me with the same problem, I'd still need at least 3 devices powered from the same source.
Very Unhelpful.
If you read the title I'm talking about my Raspberry Pi which does not provide full power from the HUB.
The 2 USB ports attached to the Pi aren't driven by the full USB standard due to the limitations of the board so I was going to extend these off into more USBs (because I need more anyway) and provide power to 2 of them, leaving me with 2 fully powered sockets, and 2 still partially powered sockets.
The additional 2 ports aren't for interaction and are just for a charging port for my keyboard and something else.
Also if I was to add my own USB HUB I'd still need to put power into this, hence leaving me with the same problem, I'd still need at least 3 devices powered from the same source.
Very Unhelpful.
closed account (S6k9GNh0)
Uh, btw, you do realize I meant a HUB that has its own power source right?
http://www.amazon.com/Plugable-Port-Speed-Power-Adapter/dp/B003Z4G3I6
http://www.amazon.com/Plugable-Port-Speed-Power-Adapter/dp/B003Z4G3I6
closed account (S6k9GNh0)
And while I was going to ignore it, I think it's worth mentioning.
I provide information "for free". I volunteer to come onto this forum and help people since I can sympathize with others on their search for knowledge or reconciliation. You come onto this forum, ask for advice, and then blatantly insult me when I offer a suggestion. Why would you possibly expect help afterwards?
I provide information "for free". I volunteer to come onto this forum and help people since I can sympathize with others on their search for knowledge or reconciliation. You come onto this forum, ask for advice, and then blatantly insult me when I offer a suggestion. Why would you possibly expect help afterwards?
5V6A.
All their + to source's + all together.
Same for the - pole.
Always take into account external devices you will power up.
In case, increase A's.
Just be careful and don't touch the powered wires.
5V x 6A = 30W.
@cquip: because like a family, we discuss but still help each other, and just in case, we try to stop people from discussing.
Just relax you both. c:
All their + to source's + all together.
Same for the - pole.
Always take into account external devices you will power up.
In case, increase A's.
Just be careful and don't touch the powered wires.
5V x 6A = 30W.
@cquip: because like a family, we discuss but still help each other, and just in case, we try to stop people from discussing.
Just relax you both. c:
Last edited on
Closed account? Rage quit?
@CQuip I know what you meant by a powered HUB but I want everything to go into a single battery, I need to split the battery power between all the devices. As I said, even if I did use a powered HUB I'd still need to power this HUB by some means, and still the Pi and LCD.
Also I want to apologise for how snappy I came across, I don't realise how aggressive I get at 4am for no reason at all.
@SGH, But doesn't the current divide through a circuit dependent upon each paths resistance. i.e. If I have 2 paths to power, the components on one path are 10x more resistive than the other then I'd get a current split of 10:1, rather than 1:1
Also I need the system to be dynamic. If I've got all 6 devices plugged in I don't want to turn one device off and it blow all the other devices through too much current.
This is why I asked for help, I can't see how this could be done in such a way that it's safe, and dynamic... Mostly because I don't have much knowledge of electrical systems though.
@CQuip I know what you meant by a powered HUB but I want everything to go into a single battery, I need to split the battery power between all the devices. As I said, even if I did use a powered HUB I'd still need to power this HUB by some means, and still the Pi and LCD.
Also I want to apologise for how snappy I came across, I don't realise how aggressive I get at 4am for no reason at all.
@SGH, But doesn't the current divide through a circuit dependent upon each paths resistance. i.e. If I have 2 paths to power, the components on one path are 10x more resistive than the other then I'd get a current split of 10:1, rather than 1:1
Also I need the system to be dynamic. If I've got all 6 devices plugged in I don't want to turn one device off and it blow all the other devices through too much current.
This is why I asked for help, I can't see how this could be done in such a way that it's safe, and dynamic... Mostly because I don't have much knowledge of electrical systems though.
Last edited on
Okay, my grandad answered this one for me, although I suppose SGH got there first and just my ideas of electricity were confusing me.
I thought that both Voltage and Current are supplied by a power source, but I've been corrected as only a voltage is supplied and the current is drawn by devices? And they draw whatever they need and no more (if nothing breaks).
I thought that both Voltage and Current are supplied by a power source, but I've been corrected as only a voltage is supplied and the current is drawn by devices? And they draw whatever they need and no more (if nothing breaks).
@Satsuma: The voltage is the same for every device directly connected to the supply.
Based on a device's resistance, it'll use more or less intensity (Power supplies still have a maximum intensity tho, but that's the 6A i meant, and you can increase it if you increase the amount of devices to power-up).
This is a little schematic made on the fly:
This device draws all the 5V from the supply, reaching at most 6A.
It may still use only 1A tho, there's no issues.
The two devices now take both 5V.
Based on the current they waste, they may use more or less current than the other device.
Usually they just have a plainly split current, 3A the first, 3A the second.
But it may be unevenly split, like 1A and 5A.
But, If you need them to have 3A and 5A, you must get a 8A supply.
Based on a device's resistance, it'll use more or less intensity (Power supplies still have a maximum intensity tho, but that's the 6A i meant, and you can increase it if you increase the amount of devices to power-up).
This is a little schematic made on the fly:
Supply (5V6A)
+ -
---| |---
| |
---( )---
^ Device
|
This device draws all the 5V from the supply, reaching at most 6A.
It may still use only 1A tho, there's no issues.
(5V6A)
+ -
---| |---
| |
---( )---
| |
---( )---
|
The two devices now take both 5V.
Based on the current they waste, they may use more or less current than the other device.
Usually they just have a plainly split current, 3A the first, 3A the second.
But it may be unevenly split, like 1A and 5A.
But, If you need them to have 3A and 5A, you must get a 8A supply.
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