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Topic: Arduino Breadboard Voltage error troubleshoot help (Read 1 time) previous topic - next topic

baligena

Feb 11, 2013, 04:39 pm Last Edit: Feb 11, 2013, 07:35 pm by baligena Reason: 1
I have an arduino on a breadboard and having an issue with the voltage on the digital pin 13 outputing an low voltage when connect to a volt regulator.  Why is this happening? because when the breadboard is connected to an Arduino UNO power that is connected to the same power supply it works perfectly fine.  See images and descriptions below.  Thank you for the help.

Notes: Power wires are connected at the bottom of the breadboard
Components:
Arduino on breadboard
Power Jack
9v - 300mA Power
L7805CV 5voltage regulator

Arduino Code:
Set to output LIGHT ON on digital pin 13


The voltage on the rails when breadboard is connected to power is 5 volts


The voltage on digital pin 13 when connected to power is 0.370 volts (why?)



The voltage on the rails when connected to arduino power is 5 volts



The voltage on digital pin 13 when connected to arduino power is 4.74 volts


Why is the voltage on digital pin 13 not the same when connected to an Arduino Uno Power to an Power supply using a voltage regulator?

Dr_Ugi

#1
Feb 11, 2013, 05:43 pm Last Edit: Feb 11, 2013, 05:45 pm by Dr_Ugi Reason: 1
Two things:

Firstly, I assume that you have links at the bottom of the breadboard, out of the photo, which link the power rails on the two sides of the breadboard.

Secondly, have you tried a electrolytic smoothing cap (say 47uf or 100uf) on both the input and output of the regulator?

It's a bit difficult to see from your photos but the regulator appears to be connected up correctly and if you are not changing the Arduino wiring then that should not be making the difference.  That leaves the following differences:

The Arduino is connected at the other side of the BB - is the power not connecting across to both sides?  Is there a dodgy contact in the BB?

The Arduino has smoothing capacitors - try adding those.  A 100nf ceramic across the power pins of the chip would not hurt either.

I struggle to see what else it can be.

Ugi

baligena

#2
Feb 11, 2013, 07:36 pm Last Edit: Feb 11, 2013, 07:42 pm by baligena Reason: 1
Quote

The Arduino is connected at the other side of the BB - is the power not connecting across to both sides?

Yes breadboard have connecting wires at the bottom to the other rails.  As you can see on picture 3 Im testing the voltage on the opposite side of where the Arduino wires are connected to the rails.

The voltage regulator seems to be working fine because its taking in 9v and converting it to 5 volt but when it goes thru the chip its not outputing the correct voltage.  Why is that?

xl97

It was suggested that you put some electrolytic caps on the input and output caps of the voltage regulator because this will help SMOOTH out the ripple the battery pack/regulator is putting out.

having a nice stable power supply to 'start' from is key......  :)



baligena

Ok it works.  That shows how important a simple capacitor has on a circuit.  I added a 22uF electrolytic capacitor to the rails and it worked.  See picture below.



Dr_Ugi


Ok it works.  That shows how important a simple capacitor has on a circuit.  I added a 22uF electrolytic capacitor to the rails and it worked.  See picture below.


Good stuff!

Amazing what a difference it can make isn't it!

I have had the same experience with decoupling caps - a tiny 100nf ceramic across the power pins can make the difference between a circuit that crashes and resets constantly and a rock-solid board.

I read somewhere on this forum that an inexplicable error is most commonly an issue with power noise - worth remembering!

Ugi

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