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Topic: How much current through V_in and GND pins? (Read 1 time) previous topic - next topic

tmmlrd

Sep 24, 2012, 03:43 pm Last Edit: Sep 24, 2012, 03:48 pm by tmmlrd Reason: 1
I have to drive some high power LEDs (using TIP122 darlingtons), for a total current around 2 A on 12 V input. I'm wandering if I can drain this current from the V_in and GND pins of the Arduino Uno board, just connecting a 12 V supply to the Arduino board and using it to power both board and loads, or if there is a (lower than 2 A) current limitation on V_in. In the former case I presume I have to "duplicate" the power supply connection and provide current directly from supplier to loads, without using V_in pin...
Hope my question is clear enough.
Thank you very much for help.

P.S. There was a similar question here http://arduino.cc/forum/index.php/topic,16348.0.html but I don't think the answer given there is right since there should not be any regulator between supply and V_in on Arduino board. However, there is between supply and +5V (this was the answer) but that's a different story... My concern is mainly about burning some traces on the PCB with a current as high as 2 A or so.

retrolefty


I have to drive some high power LEDs (using TIP122 darlingtons), for a total current around 2 A on 12 V input. I'm wandering if I can drain this current from the V_in and GND pins of the Arduino Uno board, just connecting a 12 V supply to the Arduino board and using it to power both board and loads, or if there is a (lower than 2 A) current limitation on V_in. In the former case I presume I have to "duplicate" the power supply connection and provide current directly from supplier to loads, without using V_in pin...
Hope my question is clear enough.
Thank you very much for help.

P.S. There was a similar question here http://arduino.cc/forum/index.php/topic,16348.0.html but I don't think the answer given there is right since there should not be any regulator between supply and V_in on Arduino board. However, there is between supply and +5V (this was the answer) but that's a different story... My concern is mainly about burning some traces on the PCB with a current as high as 2 A or so.


The problem with drawing 2 amps or more from the Vin pin is there is a series polarity protection diode wired between the external power connector's positive terminal to the Vin and input to the +5vdc regulator. This is a nominal rated 1 amp forward current diode, you might get away with drawing 2 amps through it but it would be exceeding it's rating, so probably not a good idea.

Lefty

fungus


I have to drive some high power LEDs (using TIP122 darlingtons), for a total current around 2 A on 12 V input. I'm wandering if I can drain this current from the V_in and GND pins of the Arduino Uno board, just connecting a 12 V supply to the Arduino board and using it to power both board and loads


Don't do it.
a) The electrical connection will be rubbish. The Arduino connectors are good for poking wires into for prototyping but not designed for high current.
b) 2A through a thin trace on a circuit board? Not good.

If you really really don't want to connect directly to the PSU then solder a wire to the power connector on the bottom of the Arduino board. There's a great big solder pad there...
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

tmmlrd

Thanks a lot, good that I realised and asked before doing  ;)
Soldering a wire could be a simple solution, but if possible, I'd like to preserve the Arduino board for other projects, so I'm thinking to realise my prototype on a breadboard shield. This is why I initially thought of using the V_in pin.
I'll move to a double connector, putting the Arduino board inside the box instead of right behind the planel. Mmmh... this means I also have to double the USB connector if I want to access it from outside. Does someone know if an extension cable for that "square" USB connector (don't know the name) exists?

Grumpy_Mike

Is is called a USB B to USB B adapter and I don't think they exist.

Far-seeker


Does someone know if an extension cable for that "square" USB connector (don't know the name) exists?


You mean something like this panel mount, Female B to Male B, USB extension cable?

tmmlrd



Does someone know if an extension cable for that "square" USB connector (don't know the name) exists?


You mean something like this panel mount, Female B to Male B, USB extension cable?


Right! This is exactly what I had in mind!
Many thanks, I'll see if I find something similar in Europe... otherwise I'll try ordering oversea. I know it would take 3-4 weeks, but could still be compatible with my development time (delivery for Crhsitmas!  :P).
Thanks to all.

Far-seeker

#7
Sep 26, 2012, 03:58 pm Last Edit: Sep 26, 2012, 04:15 pm by Far-seeker Reason: 1

Many thanks, I'll see if I find something similar in Europe... otherwise I'll try ordering oversea. I know it would take 3-4 weeks, but could still be compatible with my development time (delivery for Crhsitmas!  :P).
Thanks to all.


Adafruit has European distributors that should carry this specific item, check the tag marked "Distributors".

Edit: Also if for some reason you can't find a European supplier of this or a similar cable, you can always order a panel mount female B and standard male USB connectors, along with a small spool of the appropriate cable, and make your own extension cable.

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