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Topic: Don't apply >16V on Vin (Read 1 time) previous topic - next topic

James C4S

Nov 21, 2012, 05:20 pm Last Edit: Nov 21, 2012, 05:22 pm by James C4S Reason: 1
Like other Arduino boards, the on-board regulator is rated for an input voltage as high as 20V, even though the recommended input limit is 12V.  Being that this is a switching regulator, some might feel safer about going higher than 12V since the regulator is generating less heat / waiting power when compared to previous boards.

However, unlike the previous Arduino boards, the input capacitors on the Due are only rated for 16V.  Since it is an Aluminum Electrolytic, it probably won't fail immediately with >16V applied, however, its lifetime will be compromised.

The hardware page should list the input limit at 16V, not 20V.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

stimmer

#1
Nov 21, 2012, 06:21 pm Last Edit: Nov 21, 2012, 06:30 pm by stimmer Reason: 1
Also remember that the voltage from an unregulated 12v supply can go over 16v off-load. There were a few reports of the capacitors on the Arduino Mega exploding when powered by an unregulated 12v supply. (I can't tell for sure but the Mega capacitors might have been tantalums - the aluminium capacitors on the Due look like they will be more tolerant)

Graynomad

Yikes, just the other day I suggested that higher voltages should be OK because they have a switching regulator.

Why on earth not use a 25v cap?

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

James C4S


Yikes, just the other day I suggested that higher voltages should be OK because they have a switching regulator.

That's exactly what I thought until I saw the caps.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Palliser

Due is similar to uno regarding VIN node. We should keep the recommended input voltage between 7-12V. Supplying more than that, let's say 13V, will affect the IC1B (LMV358IDGKR) comparator input (CMP - +3V3).  When you supply a 13V, the VIN node will drop down to 12V due to D1.   The 12V is then divided into half by RN4C and RN4D to 6V, which is more than the LMV358 maximum input rating (5.5V). So, if we supply more than 12V, the LMV358 will pay.

spcomputing


Due is similar to uno regarding VIN node. We should keep the recommended input voltage between 7-12V. Supplying more than that, let's say 13V, will affect the IC1B (LMV358IDGKR) comparator input (CMP - +3V3).  When you supply a 13V, the VIN node will drop down to 12V due to D1.   The 12V is then divided into half by RN4C and RN4D to 6V, which is more than the LMV358 maximum input rating (5.5V). So, if we supply more than 12V, the LMV358 will pay.


I always wondered what that op-amp was doing in there, but I forgot to ask... Thanks!

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