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Power & Regulator Question

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UKSteve
(@uksteve)
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Joined: 2 years ago
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Topic starter  

Quick question...

I'm just wondering if i can add a USB connection to the circuit so i can either use an external OR USB supply for my +5V output. Would the regulator circuit be ok like this or would i need to stop current flowing back to the regulator if it's USB powered ?

dbwsusb

   
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robotBuilder
(@robotbuilder)
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Joined: 5 years ago
Posts: 2042
 

@uksteve

The Arduino development board can be powered by the USB or a plug in battery supply.
You might check out the circuit to see how that is done.
https://easyeda.com/ankitjain21/basic-circuit-diagram-of-arduino-uno-r3

More detail,

https://www.allaboutcircuits.com/technical-articles/understanding-arduino-uno-hardware-design/

 

 


   
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Ron
 Ron
(@zander)
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Posted by: @uksteve

Quick question...

I'm just wondering if i can add a USB connection to the circuit so i can either use an external OR USB supply for my +5V output. Would the regulator circuit be ok like this or would i need to stop current flowing back to the regulator if it's USB powered ?

dbwsusb

Yes, you need to prevent feeding back. This is just one diode AFAIK.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Will
 Will
(@will)
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Posts: 2507
 
Posted by: @zander
Posted by: @uksteve

Quick question...

I'm just wondering if i can add a USB connection to the circuit so i can either use an external OR USB supply for my +5V output. Would the regulator circuit be ok like this or would i need to stop current flowing back to the regulator if it's USB powered ?

dbwsusb

Yes, you need to prevent feeding back. This is just one diode AFAIK.

A diode will cause a voltage drop though. Even a Schottky will lose a couple of tenths or more, so this may affect the performance of your device.

Anything seems possible when you don't know what you're talking about.


   
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robotBuilder
(@robotbuilder)
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@uksteve

Another example of how the Arduino development board handles dual USB and battery power supplies.

https://cyberblogspot.com/arduino-power-supply-schematic/

To prevent back flow from one battery into the other.

batteriesInParallel

 

 

 

 

 

 


   
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UKSteve
(@uksteve)
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Joined: 2 years ago
Posts: 12
Topic starter  

Thanks for the replies,

I had a feeling i'd need to do something with this with a diode of some type which leads to one more question... Diode types ?

The protection diode is a 1N4007.

I need to order some diodes, before i do is there any other 'information' anyone would like to add, formula's, calculation's and just a little background as to how & why it's that diode type please.

I don't want to just add the diode and say 'yes it works', i'd like to have a bit more of an understanding of the how and why it works as well... i'd like to learn more !!! (never said that a school) 😉


   
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robotBuilder
(@robotbuilder)
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Joined: 5 years ago
Posts: 2042
 

@uksteve 

I'm just wondering if i can add a USB connection to the circuit so i can either use an external OR USB supply for my +5V output.

Your question is not so much a parallel power supply problem but a dual power supply problem.

Well the Arduino developer board can use either and switches automatically between power supplies see above links to how it is done.

The voltage drop mentioned for a diode can be reduced by using p channel mosfet zero loss diode equivalent.

batteriesInParallel2

Components have current and/or voltage limitations so it is a matter of looking at the specs for the various components.


   
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