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(@pbruno3)
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Joined: 2 years ago
Posts: 239
February 21, 2019 5:51 am  

9V wall wart... is it a switching power supply (aka quality) or just a regular one (the weight is often a hint, with heavy being junky linear or non-switching type).

Yes to the last question.


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(@oakbarn)
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Joined: 8 months ago
Posts: 64
February 21, 2019 3:56 pm  

Not sure after trying to find the specs.  It was for  Arduino Mega and Uno on Amazon but we know what that means.  It is likely non switching.  I will replace with better.  There is one on Amazon that is switching for about twice the price I paid.  It is still on line after 2 days. 


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(@natebrews)
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Joined: 6 months ago
Posts: 12
March 3, 2019 9:09 pm  

I have been seeing some problems at power up on my Mega when using the 5V/3A DIN supply in the order list.  If I power the part up after the supply is up then it works ok, but if I have it connected at powerup (AC power switch turned on) the ethernet shield  (5100) blinks twice and then does nothing.  If I pull the plug on the Arduino and then plug it back in (using the USB plug to connect to the power supply), it will connect and work fine.  

 

It looks like there is something about the powerup of that supply that the Mega doesn't like, or maybe it is just mine.  I have tried adjusting the voltage up and down a bit (4.85V-5.05V) and the behavior is the same.  

 

I guess I either need to have a different supply feeding the Mega or maybe a power on delay or such for the mega/5100.  I have tried powering via the USB port, 5V terminal, and VIN.  All gave the same result.  In or out of the DIN carrier didn't matter (I thought maybe the connected circuits were messing something up).

 

Is it just me?  I assume others are using a similar configuration since it is the parts from the order list.


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(@natebrews)
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Joined: 6 months ago
Posts: 12
March 3, 2019 9:31 pm  

So, my power on theory seems to have played out. 

After trying to come up with some complicated way to do it I had a moment of clarity.  Placing a cap on the RESET pin will delay the turn on by the internal pull up into the cap.  I placed a 4.7uF cap between RESET and GND and now it powers up and works fine.  

I haven't looked at it with a scope, but I'm guessing the startup of that power supply isn't as nice as it could be.


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(@pbruno3)
Estimable Member Admin
Joined: 2 years ago
Posts: 239
March 4, 2019 1:20 am  

That’s brilliant!!

I actually solved an aberrant reset problem with an open reset pin on a feather by tying it with a capacitor... seems similar. 


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(@oakbarn)
Trusted Member
Joined: 8 months ago
Posts: 64
March 4, 2019 2:12 am  

I have 9 volt switching PS now.  Have twenty five 4. 7 uf Capacitors coming next week (ebay for $3.99)  I have attached a diagram of what I think the circuit is. 

 

I know nothing about alot,  a little about a lot, but not this lot!


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(@natebrews)
Active Member
Joined: 6 months ago
Posts: 12
March 4, 2019 2:15 am  

That is what mine has on it now.  I have flipped the power switch probably 10 times on it and haven't had a problem yet.  If it is polarized (like an electrolytic) make sure the - side is GND.

This post was modified 5 months ago by natebrews

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