Go Down

Topic: HD44780 LCD; contrast works on Arduino, but not Boarduino [RESOLVEDish] (Read 1 time) previous topic - next topic

JoeO

The easiest way to test for bad capacitors is to use an oscilloscope and look for ripple or noise on a power line.
If you can't do that, just replace the power supply capacitors.
However, when you power it with the USB directly, the supply should not drop to 3.3V. 
When you run from the USB power, what pins are jumpered on JP4 and the power select jumpers.

RJFalconer

#6
Dec 24, 2011, 02:24 pm Last Edit: Dec 24, 2011, 02:44 pm by RJFalconer Reason: 1

The easiest way to test for bad capacitors is to use an oscilloscope and look for ripple or noise on a power line.
If you can't do that, just replace the power supply capacitors.

Alas, I have no such equipment. I'd prefer not to try to replace unless they're definitely faulty.


However, when you power it with the USB directly, the supply should not drop to 3.3V.  
When you run from the USB power, what pins are jumpered on JP4 and the power select jumpers.

I have "USB" selected on the power jumper. (I assume that's the same jumper as jp4)

When powered by USB:
According to my very old multimeter, my Arduino gives 6v across 5v-ground.
My Boarduino "5v-ground" gives 4v with no load, with full LED backlight, and with 330 ohm limited backlight. Perhaps it's not a power issue after all.

When powered by 9v external:
Arduino 6v
Boarduino 6v no load, 6v with LED fullbright, 6v with current-limiting 330 ohm resistor.

JoeO

OK, something is wrong.  You should not see 6 V on the 5 V line.
Are you near a Harbor Freight store?  They typically have a digital MM for $3 on sale, $5 regular price.
Or you can try reading a fresh, unused 1.5V battery. 
 

RJFalconer


OK, something is wrong.  You should not see 6 V on the 5 V line.
Are you near a Harbor Freight store?  They typically have a digital MM for $3 on sale, $5 regular price.
Or you can try reading a fresh, unused 1.5V battery.

New-ish 1.5v shows as ~1.8.
Brand new 9v shows as ~11v read directly, and 6v again on arduino.

(So I would say that it looks like my analogue reader is a little off, but powersupplies are OK)

There's unfortunately no chance of me picking up a reader at 4pm Saturday Christmas Eve.

floresta

Quote
Brand new 9v shows as ~11v read directly, and 6v again on arduino.

No matter how inaccurate your meter is it will not read higher than it is supposed to for one reading and lower than it is supposed to for another.  Your readings indicate that your Arduino is drawing excessive current which is lowering the voltage delivered by the battery.

To see if this is what is happening you can try the same set of measurements with the Arduino.


Don

Go Up