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[on:]

[Edit: Problem is fixed from my perspective. Still no idea why contrast is different on arduino/boarduino though, when in usb power]

Christmas help needed!

Hello all,

Earlier I had my 16 pin 16*2 HD44780 LCD connected up to my Arduino, and all was working perfectly.

I soldered it to my Boardunio, and now my contrast is very low. (Barely visible, with my 10k pot turned all the way to one direction). My pot has ground/+5v on either side, with LCD pin 3 in the centre. I've also tried without the +5v connected to the pot; result is the same.

Oddly, if I power the boarduino with an external battery (rather than usb header) the contrast is *better* (but still bad) but then fades to the "bad" level.

I have current-limiting resistors (2*330 Ohm in parallel) on the backlight LED.

When I change to a blank sketch I only see very feint "blocks" on the top row of the LCD.

I'm desperately trying to finish this off before Christmas, so any help would be much appreciated!

----

Extra details (wire colours given for later pictures):
 * LCD RS pin (4, yellow) to digital pin 12
 * LCD Enable pin (6, blue) to digital pin 11
 * LCD D4 pin (purple) to digital pin 6
 * LCD D5 pin (grey) to digital pin 5
 * LCD D6 pin (white) to digital pin 4
 * LCD D7 pin (black) to digital pin 3
 * LCD R/W pin (green) to ground
 * 10K potentiometer:
 * ends to +5V and ground
 * wiper to LCD VO pin 3 (orange)
 * Pin 0 unconnected, used to seed random(). Digital pin 7 soldered up and floating, for later use as a switch.

Image album;
http://imgur.com/a/zKHe1

Working with arudino + back of breadboard soldering:


Set-up with boarduino:


Soldering:

[Reply #1 on:]

Even with a blank sketch I only see very feint "blocks" on the top row of the LCD.

A row of blocks on the top row of the display indicates that the controller on the LCD module is not being initialized properly.  This could be due to incorrectly written software but assuming you are using the same sketch as before that is not likely.  It could also be due to improper connections which your photographs should let us evaluate.  Another cause could be the relatively large current for the LED backlight causing the voltage to sag below 5v.  You should check the Boarduino +5v pin both with and without the backlight connected.

Don

[Reply #2 on:]

Ty for your prompt reply!

Even with a blank sketch I only see very feint "blocks" on the top row of the LCD.

A row of blocks on the top row of the display indicates that the controller on the LCD module is not being initialized properly.

Sorry, I should clarify; when uploading an empty program (literally just the "BareMinimum" example sketch) *then* and only then I see the black squares. My main sketch shows text fine (LCDCrystal library is amazing!).

Another cause could be the relatively large current for the LED backlight causing the voltage to sag below 5v.  You should check the Boarduino +5v pin both with and without the backlight connected.

Checking the +5v is a good plan. I'll see if I can find a voltmeter. Do I check across +5v->ground?
I read somewhere that I need "at least 30-40 ohms" on my backlight. I think I have 165 atm. Is that likely to be insufficient?

Edit: I get ~3.5v with and without the LED connected :S. Bad board?

[Reply #3 on:]

Your Power Source is bad or the 5 V reg on Boarduino is bad(unlikely).

If you are getting power from USB - Try another USB port.
If from Ext 9V supply - Check to make sure it is 9V+.  Or just try another supply.
Ext 5V supply - Try another supply. The supply is either bad or it is being loaded down.

[Reply #4 on:]

Your Power Source is bad or the 5 V reg on Boarduino is bad(unlikely).

If you are getting power from USB - Try another USB port.
If from Ext 9V supply - Check to make sure it is 9V+.  Or just try another supply.

I have the same problem with both USB and ext 9v supply. I've tried other batteries.
Mmm. I did (briefly) connect a 9v battery at incorrect polarity to the boarduino (toying with the idea of removing the DC jack, so was just holding wires to contact points on the underside). Perhaps I've damaged one of the power capacitors. How can I tell if this is the case?

[Reply #5 on:]

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.

[Reply #6 on:]

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.

[Reply #7 on:]

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. 
 

[Reply #8 on:]

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.

[Reply #9 on:]

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

[Reply #10 on:]

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.

Aren't those two numbers both higher than expected? (11v instead of 9v, 6v instead of 5v?) I don't mean for this to sound like a snarky question; sorry if it sounds as such.

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

Can you expand on that?
I think I've measured all combinations of boarduino/arduino battery/usb.

[Reply #11 on:]

Haha!
You guys are *awesome*.

I re-connected the wires I was tinkering with, and with the *new* battery, it all works!
Hopefully this will work as a long term solution.

I shall resolder everything and report back.

Edit: interestingly, the contrast is still bad when connected to USB (after moving the power select jumper ofc) but it does not matter; project will be battery powered after all.

[Reply #12 on:]

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.

Aren't those two numbers both higher than expected? (11v instead of 9v, 6v instead of 5v?) I don't mean for this to sound like a snarky question; sorry if it sounds as such.

It's not snarky at all - my answer was a bit messed up.  I missed the fact that you were testing the battery while connected to the Arduino and not to the Boarduino.  I also assumed that you were keeping the voltmeter connected to the battery while connecting the Arduino/Boarduino to the battery.

Don

[Reply #13 on:]

Ah ok, ty for the clarification

AND TY ALL! MERRY CHRISTMAS!

You guys have saved this project present. My sister will be most pleased. All working, now to finish the mounting and finally go to bed.

To all a good night!