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[on:]

I finally decided to purchase an LCD screen to mess around with. Once it arrived, I hooked it up the same way it was in the Arduino IDE example files for LiquidCristal. Any time that I hook the LCD up to 5V+ on the VCC pin, and the ground to the VDD pin, the Arduino shuts off until the load is removed, making me think it's drawing too much power. I have tried using resistors on the VCC for the LCD, but either it does nothing, or shuts my Arduino off until I remove the load.

Useful info:
-Using an Arduino Duemilanove
-Tried powered by USB (5v), tried alternate power supply (12v). Both did not work.
-Not using a 10k wiper potentiometer on Pin 3 (Vo), I don't have one. I do have a 50k potentiometer.
-Tried using 10k ohm resistor on pin 3. Does not work.
-Tried with just power going to the LCD (no data lines), still turns off the Arduino.

The LED on the LCD works, which is a good thing.

My LCD screen: https://www.inventables.com/technologies/lcd-module
I couldn't find a datasheet to upload, but I do have the datasheet on paper in front of me.

The datasheet says that the max draw of power is only 4mA when the Arduino puts out 20mA per pin I believe. I have no idea how much the 5V pin can put out.

If you could at least confirm that my LCD is drawing too much power, I would be grateful.

[Reply #1 on:]

What I'd do is :

put something like a 100-200 ohm resister in the 5V to the LCD and connect just that and GND, then measure the voltage drop across said resister.  That will give you the current with ohms law, if its much more than 4mA its a faulty LCD or a fault in your wiring. 

[Reply #2 on:]

Any time that I hook the LCD up to 5V+ on the VCC pin, and the ground to the VDD pin, the Arduino shuts off until the load is removed, ...

The LED on the LCD works, which is a good thing.

  Did you use a current limiting resistor?  If not then your LED is probably drawing enough current to shut down the Arduino power supply.  Start with 150 ohms in series with pin 15.

You haven't mentioned the presence of smoke, but how about heat?  If your epoxy blobs are getting hot then your power leads (pins 1 and 2) are reversed.  Some LCD modules, especially the inexpensive ones) have these reversed.

-Tried with just power going to the LCD (no data lines), still turns off the Arduino.

This is a very good idea.  Try connecting just pins 1 and 2 again and check for heat.  If it stays cool then use your 50K pot and see if you can get a display of a single row of blocks on your screen.

Don

[Reply #3 on:]

What I'd do is :

put something like a 100-200 ohm resister in the 5V to the LCD and connect just that and GND, then measure the voltage drop across said resister.  That will give you the current with ohms law, if its much more than 4mA its a faulty LCD or a fault in your wiring. 

Could you explain this a little better please? I didn't quite understand what you were getting at.

You haven't mentioned the presence of smoke, but how about heat?  If your epoxy blobs are getting hot then your power leads (pins 1 and 2) are reversed.  Some LCD modules, especially the inexpensive ones) have these reversed.

I have tried both ways, and the datasheet mentions the first pin is Ground, and the second is 5V+.

This is a very good idea.  Try connecting just pins 1 and 2 again and check for heat.  If it stays cool then use your 50K pot and see if you can get a display of a single row of blocks on your screen.

Even by connecting pins 1 and 2, the Arduino still gets shut off. I'm going to try hooking up the LCD power to 5V from USB to see if that works.

EDIT: Just tested the external power supply, it turns off the power supply until I release the load. The power supply was an AC to DC converter. Rating: 120VAC to 5V 1A DC. I can't figure out the problem, and it's really starting to bother me.

[Reply #4 on:]

I Think you now have a Brick... If the data sheet was correct...

Doc

[Reply #5 on:]

I Think you now have a Brick... If the data sheet was correct...

Doc

Damn. Well, at least I didn't spend any money on it. I was given a $20 gift card to the website. The thermistors I got from there work!

[Reply #6 on:]

You didn't answer my question about the series resistor for the LED backlight.

Don

[Reply #7 on:]

You didn't answer my question about the series resistor for the LED backlight.

Don

The LED backlight is fine, the LCD seems to be blown.

[Reply #8 on:]

The LED backlight is fine ...

Maybe, but then again it may just seem to be fine.  You STILL haven't answered my question.

the LCD seems to be blown.

Maybe, but then again it may not be blown.  

You didn't answer my question about heat.

Have you checked your wiring for shorted pins?  Have you considered posting a photograph so we could check?

Pluggy gave you a good tip in his reply #1 but he didn't follow up when you asked "Could you explain this a little better please? I didn't quite understand what you were getting at".  Here's the explanation: Add a resistor in series with pin 2.  Measure the voltage across that resistor.  Divide the voltage you just measured by the resistance of the resistor to calculate the current through the resistor.

Don

[Reply #9 on:]

You didn't answer my question about heat.

I can't accurately answer your question. I tried applying power for .2 seconds, and I did not feel any heat, see any smoke, nor smell anything funny.

Have you checked your wiring for shorted pins?  Have you considered posting a photograph so we could check?

Yes I have checked it. Everything looks fine to me. I will post a few photographs once I find my camera which should be sometime today.

Add a resistor in series with pin 2.  Measure the voltage across that resistor.  Divide the voltage you just measured by the resistance of the resistor to calculate the current through the resistor.

Whenever I try to do that, my Arduino turns off when the load is applied and I can't get a reading from my multitester.

[Reply #10 on:]

A 200 ish ohm series resistor is within the current capabilities of an arduino digital pin even with whatever else is in circuit being a dead short circuit. It shouldn't reset the arduino whatever happens.  The 5V rail in the arduino is good for around 200 mA - it shouldn't have any issues with anything down to 33 ohms with a short circuit downstream of it.  Forget the LCD and connect the resister directly between 5V and GND.  If you've tried the resister in series and it still resets, then logically it will reset with just the resister, if that's the case you're got an iffy Arduino

[Reply #11 on:]

There is still the possibility that excessive current is being drawn by the backlight LED and that is loading down the power supply.

Don

[Reply #12 on:]

Which is why I said just connect the GND & 5V.  With the right colour panels (Black on Green), they work without the back light anyhow.