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PHOBoS
Joined: Jan 14, 2010
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 Posted: Sat Apr 06, 2019 4:41 am Post subject:
external 5V supply + USB ? |
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Is there a way to be able to use an external 5V supply but still have the option to plug in USB for programming ?
I could install a switch but that has the chance of forgetting it one day and maybe damaging the arduino or USB
port of my computer.
hmm, it looks like there is a schottky diode between the 5V from the USB and the rest of the arduino, so that
should already work, right ? (maybe with an extra diode between external 5V and arduino 5V input)
FYI: I am using an arduino nano (clone) to control some addressable LEDs.
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blue hell
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| Posted: Sat Apr 06, 2019 8:00 am Post subject:
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Two diodes should work .. like
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o---|>|---+
+----o
o---|>|---+
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Is there no schematic? thought arduinos to be open sourced ...
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also .. could someone please turn down the thermostat a bit.
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Grumble
Joined: Nov 23, 2015
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| Posted: Sat Apr 06, 2019 8:37 am Post subject:
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I do that, I have a dual 12volt euro connector and on the arduino nano an usb connector.
For programming I plug a usb power supply in the nano and program it with an icsp Dragon programmer. When the programming is done I use the euro connector, feeding the +12volt into the Vin of the arduino.
I do not use the arduino platform, but atmel studio with an added arduino functionality.
edit: you can also put 5volt to the Vin (sometimes called RAW input) and it will still work
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Last edited by Grumble on Sat Apr 06, 2019 8:45 am; edited 1 time in total |
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Grumble
Joined: Nov 23, 2015
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| Posted: Sat Apr 06, 2019 8:41 am Post subject:
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PHOBoS
Joined: Jan 14, 2010
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| Posted: Sat Apr 06, 2019 8:59 am Post subject:
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| Blue Hell wrote: | | Two diodes should work .. like |
Yes, that's what I was thinking since there is already a diode between the USB connector and the rest of the 5V on the arduino.
The 5V is the output of a voltage regulator but apparently it's not a problem to supply 5V to that, although I always add a diode
between it and the Vin just in case.
| Quote: | | Is there no schematic? thought arduinos to be open sourced ... |
Schematics are easy to find which is how I know about the diode, I also measured it since I have a clone.
oh, grumble already posted one 
I think that with 12V you can just use the Vin, but I only have 5V.
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Grumble
Joined: Nov 23, 2015
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| Posted: Sat Apr 06, 2019 11:23 pm Post subject:
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The voltage/frequency dependancy is more or less linear, so if 10Mhz needs at least 2.7 volt and 20Mhz needs 4.5 volt, the atmega328 will run perfectly at 16Mhz @ 3.8 volt.
The power suply chip LM2940 used in the original Nano is a low dropout regulator with a dropout of about 0.5 volt, so when powered from 5 volt you are just fine!
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