[SOLVED] LCD 2x16 I2C powering down Arduino Uno

When I connect my Luxorpart LCD display 2x16 serial I2C to my Arduino Uno, the LCD powers up for a second, then both the LCD and the Arduino power down. As soon as I unplug either the 5V or ground, the Arduino powers up again. This happens regardless of whether any code in loaded into the Arduino or not.

I believe I’m connecting everything correctly:
GND <—> GND
VCC <—> 5V
SDA <—> A4
SCL <—> A5

I’ve Googled what the issue could be but no-one seems to have reported this issue previously. Could someone please advise if the problem is with the I2C, the LCD, the Arduino, or all three?

Might be a short between Vcc and Gnd on the LCD module.

Probably none of the three.

I suspect your problem is that you are attempting to power the Arduino via its "Vin" or "Barrel jack". The unfortunate blunder is not comprehending what the "Vin" or "Barrel jack" is. It is essentially an ornament provided in the very beginning of the Arduino project when "9V" power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle.

Nowadays, 5 V regulated switchmode packs are arguably the most readily available in the form of "Phone chargers" and switchmode "buck" regulators are cheap on eBay so these can be fed into the USB connector or 5 V pin to provide adequate power for all applications. Unfortunately, many tutorials or "instructables" are outdated or misleading and have not been updated to reflect the contemporary situation.

Since you made no mention of how you’re powering the Uno, it would be logical that’s the source of your trouble. A 9v battery will not work.

Post a link to the actual display that you have bought.

If it is a regular 16x2 with an I2C backpack, remove the backlight jumper from the backpack.

David.

p.s. it is boring to repeat

Post a link to the actual display that you have bought.

It takes you 30 seconds to do this. It means you get accurate replies.

david_prentice:
p.s. it is boring to repeat

Post a link to the actual display that you have bought.

It takes you 30 seconds to do this. It means you get accurate replies.

Or alternatively, RTFM!

OK, he has now four answers. Two more than I feel deserved until the OP actually replies. :roll_eyes:

WattsThat:
Since you made no mention of how you’re powering the Uno, it would be logical that’s the source of your trouble. A 9v battery will not work.

I'm powering the Uno through a laptop USB, both when the laptop is under mains power and when not, with the same result.

Paul__B:
It takes you 30 seconds to do this. It means you get accurate replies.

Or alternatively, RTFM!

OK, he has now four answers. Two more than I feel deserved until the OP actually replies. :roll_eyes:

I googled "Luxorparts I2C" and found this

It looks like a regular 16x2 with backpack.

Remove the backlight jumper from the backpack.
Does this solve the high current problem?

Some 16x2 are sold with 0R series resistor on the pcb for the backlight.
Most modules have 100R series resistor on the pcb.

You can replace the jumper with a 100R resistor. e.g. Dupont cables with 100R resistor in the middle. This will give a reasonable backlight brightness.

David.

Can you post some photos of your lcd & backpack including as it is hooked up to the Arduino?
Also, have a close look at the backpack and the space under it. Sometimes the backpack be soldered to close to the LCD or can bend over to the point where it can rub against the LCD metal retainer clips and short out.
Look underneath the backpack and make sure that isn't happening.

--- bill

Paul__B:
Probably none of the three.

I suspect your problem is that you are attempting to power the Arduino via its "Vin" or "Barrel jack". The unfortunate blunder is not comprehending what the "Vin" or "Barrel jack" is. It is essentially an ornament provided in the very beginning of the Arduino project when "9V" power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle.

Nowadays, 5 V regulated switchmode packs are arguably the most readily available in the form of "Phone chargers" and switchmode "buck" regulators are cheap on eBay so these can be fed into the USB connector or 5 V pin to provide adequate power for all applications. Unfortunately, many tutorials or "instructables" are outdated or misleading and have not been updated to reflect the contemporary situation.

I was powering the Uno from the laptop USB (which was connected to mains power). I was going to try using something like in the link following, but from what you're saying, it would be unlikely to help:

SongOfSickness:
I was going to try using something like in the link following,

I wouldn't. These types of devices normally don't draw anywhere near enough current to cause the type power issue you are seeing, even if the LCD backlight has a 0R resistor.
You can try pulling the jumper on the backpack to see if that helps. If it doesn't, then the back-light is not the issue and it is likely there is a wiring issue, or a short somewhere on the backpack.
Post some photos so we can take a look what you have.

--- bill

See attached photos of LCD with I2C. Link to part purchased here:

2018-12-27 21.21.53.jpg

2018-12-27 21.22.20.jpg

2018-12-27 21.20.20.jpg

2018-12-27 21.20.51.jpg

2018-12-27 21.21.53.jpg

2018-12-27 21.22.20.jpg

SongOfSickness:
I was powering the Uno from the laptop USB (which was connected to mains power). I was going to try using something like in the link following, but from what you're saying, it would be unlikely to help.

It most certainly would not help if connected to the "Barrel Jack" but set to 5 V and connected directly to the "5v" and ground of your Arduino, it would be a good way to power it.

Well now, we have photos of your parts and know what they are, but not how you have connected it.

Start "at the beginning". Connect Vcc and ground only from the display to your Arduino. See what happens. If it does the same thing, pull the backlight jumper off the backpack and see what happens then. The backlight will not light if the jumper is removed, but you will see whether the pilot light on the Arduino stays on.

R8 - the backlight resistor - is indeed "101" or 100 Ohms on the LCD module, though it is not the same module illustrated on the Luxoparts site which shows R9 as well. Nor the same backpack! :astonished:

Problem solved. Got a replacement unit, new unit seems to work fine. Thank you all for your assistance.

SongOfSickness:
Problem solved. Got a replacement unit, new unit seems to work fine. Thank you all for your assistance.

Please modify the topic of your first post on this thread to add “[Solved]” at the start.