Printrboard headaches and LCD voltage

[Thew]

I decided I would pony up the cash for the Printrbot LCD module. I downloaded the updated firmware when the LCD arrived and installed it. It seemed to work great and and I was off running without the laptop.
The only problem was that the cooling fan no longer worked, mine worked before but there seemed to be a bug in the firmware. I thought no problem I would fix the firmware.

After downloading every firmware I could find that was supposed to be set up to work on my PB LC (Rev D board) and testing them all I found every one of them crashed.
I had some just stop and the LCD went blank, Had to shut off the PB to restart it. Some had one of the steppers go nuts and run until it hit the stops. None work except the MarlinLCD.

So I decided to try the Printrbot-LCD-Extrudr-Firmware-master firmware without the LCD plugged in, I noticed that the LCD got much warmer than I thought it should when it did run . The new firmware ran flawless.

I decided to look at the wiring of the LCD, I noticed the part number of the LCD NHD-0420A-FL-GBW-33V3 . I pulled up the datasheet and looked over the Printrboard schematics.

Then it hit me, the LCD Printrbot sold me was 3.3v and not 5v. WTF?

So I'm giving everybody a warning, If you bought the LCD from Printrbot you better check the LCD voltage. This has caused me many hours of frustration flashing my firmware over and over only to find I still had problems.

Specs.
Printrbot LC Rev D
GT2 Belts
Printrbot LCD

[Tdeagan]

Fascinating!!

I can't see the LCD part# on my Printrbot purchased LCD. Did you have to desolder your's to see it?

[Thew]

I bent mine enough to read the part number but I would recommend desoldering it. Now I cant bend it back to be flush with the board so I will have to desolder it anyway. I guess I will use the LCD with my Teensy 3.0 projects.

[Tdeagan]

I peeled the sticker with the part number out with a probe. Sure as shinola, you're right, mine is:
NHD-0420AZ-FL-YBW-33V3

Data Sheet

3.3V , 3.0V backlight. And this is _clearly_ being powered by a 5V pin off the Printrboard.

Great catch!! Now, what to do next?

[Tdeagan]

You're dead on the money. The LCD part is a 3.3V LCD (I peeled the sticker with the partnum out with a dental probe.)

NHD-0420AZ-FL-YBW-33V3

Data Sheet

3.3V , 3.0V backlight. And this is _clearly_ being powered by a 5V pin off the Printrboard.

Aargh. (and great catch by Thew!)

[Thew]

I would like Printrbot to send us the right LCD since thats what we paid for.

I'm going to use one of the LCD's in my junk box, I have a bucket of them Ive collected over the years. I could use this 3v3 LCD with one of my Teensy 3.0 projects.

I'm glad I found this out so others wont be in the same boat.

BTW Im also a HAM (KD7VUG)

[Mooselake]

BTW Im also a HAM (KD7VUG)

There's several of us here. Probably has something to with the magic smoke.

Kirk, KC8MMU

[lwalkera]

I said this in another thread, but if you don't mind lack of a backlight, you can disable it by desoldiering the solder jumper on the back of the LCD board to the right of the pin headers. If not, you could probably replace the dropper resistor that's there with the correct value for 5V. The IC for the LCD appears to be able to work with either 5 or 3.3 volts, it's only the dropper resistor that appears to be different between the two models.

(I have a ham license, KI6APQ, but never really did anything with it. Hoping to get more into it with http://www.kickstarter.com/projects/mos ... r-platform .)

[RetireeJay]

BTW, I was a ham once too: K1YAZ. But that license expired around 1972. I was living in apartments that didn't allow antennas, so I went into photography instead of radio as my hobby. Now I don't have time to think about ham radio; the Printrbot and photography - and grandkids - (and a few other projects) take up all of my time.

[Mochaboy]

I said this in another thread, but if you don't mind lack of a backlight, you can disable it by desoldiering the solder jumper on the back of the LCD board to the right of the pin headers. If not, you could probably replace the dropper resistor that's there with the correct value for 5V. The IC for the LCD appears to be able to work with either 5 or 3.3 volts, it's only the dropper resistor that appears to be different between the two models.

(I have a ham license, KI6APQ, but never really did anything with it. Hoping to get more into it with http://www.kickstarter.com/projects/mos ... r-platform .)

I backed the project - buying an unpopulated PCB

If you guys want to do some hardware hacking, you can buy a pololu 3.3v step down regulator and just solder it inline to the LCD. It'll be ugly but, it's not a terrible amount of work for a $4 part.

[plexus]

Why not just build a buck converter on the board for a proper 3.3V supply? you are looking at what, maybe a total of $2 max of total cost to build in a voltage converter. anyway... good luck with your LCD panels. hopefully they don't pop on you.

[lwalkera]

Or you could just replace the $0.10 resistor on the back of the LCD

[Tdeagan]

Is that the R7 shown in this pic?

lcd.jpg

[lwalkera]

Is that the R7 shown in this pic?

lcd.jpg

Yep

[Thew]

Ok, I have been researching this problem between work breaks

The LED in the back light does use R7 as the current limiter. I measured R7 as 3 ohms and verified with the markings. My R7 has been cooked pretty good but it still has good markings.

I measured across the LED - 2.06v @ 76ma.

My LED is not very bright at 3 volts, I suspect that its cooked too. I supplied 5v to the back light pins (15,16) and the current was about 800 ma! no wonder the printrboard was having issues.


I going to swap out the 3 ohm resistor.

And according to the data sheet (as lwalkera pointed out) the chip set can handle 5v with no problem.

Now I hope my Printrboard works with the LCD attached, the firmware I use now works great without the LCD but I never could get it to work with it. But with a 800ma draw on the power supply I suspect that the voltage regulator couldn't handle the load. The LM2841 buck voltage regulator used is optimized for 300ma with a typical draw of 525ma and a max of 900ma. Can we say overheating?

I have included some tasty pics.

EDIT: I used a 22 ohm 1/4w resistor and it works but its not as bright as before
If you remove R7 and place your resistor at R8 the back light power would be supplied from pin 2 (VDD), then only need 1 power wire

[Thew]

So I had the chance to run my PB LC last night. I scoured through my notes for all of the firmware related problems I was having. I ran some gcode I had that failed to print, it would lock up or do funny moves.
I noted that sometimes there would be a random x or y move off of the part to x0 or y0 then it would go back and continue to print , I couldn't find any bad gcode commands in the program to explain the move. This problem seems to be fixed, I had no random moves.
I noted it would randomly decide to move the z to 200mm,if I let it run after about 100mm the LCD would go blank and the printrboard would lock up and no respond. This problem seems to be fixed.
The LCD would just go blank and I would have to shut off the PB and restart it. It never went dead.

I also printed this air-duct off of Thingaverse (http://www.thingiverse.com/thing:34530) and the only problem I had is with my slicer settings.It took about 1 hour to print it.

So if you have the LCD from printrbot.com you better check it out. disable the back-light or change the resistor R7 to 22ohms. This could be the source of all of your electrical problems.

Now I'm off to print me some blobs

Case closed.

[ei8htohms]

Does anyone know the part number for the pbhq supplied 5V LCD panel? Or something about the specs that can help me verify interchangeability?

I've got one of the first batch pb put up for sale and the voltage seems fine (everything works great), but I'd like to change it out for an LCD with an amber on black display if I can find one (just to complement the steampunk aesthetic of my GO: http://ei8htohms.tinyparts.net/?p=709).

I picked up a 4x20 amber on black LCD from Amazon without thinking too much about the subtleties of connecting it to the existing panel with encoder (that came with the PB LCD panel) and it doesn't look like it's compatible based (don't laugh) solely on the fact that its connector has 10 holes and the pb LCD has 16.

http://www.amazon.com/Serial-Module-Amb ... =de_a_smtd

It looks to me like this one might work:

http://www.buy-display.com/default/char ... -20x4.html

Not only does it have 16 holes on the top edge, it lists the STU7066 IC which seems to match the New Haven display specs. It does look like it's got more business going on in the back though, so I'm not excited about just pulling the trigger (having failed once before and obviously not knowing a lot about this stuff).

Any advice about how to make sure I am looking at compatible displays?

Thanks!

_john

[Tdeagan]

See my post above with a link to the data sheet and part. Almost all of the 16 pin LCDs are interchangeable (if they're of the same voltage.)

[ei8htohms]

OK, I ordered the one I linked to (from Buy-Display). Fingers crossed. Thanks!

[JustWondering]

I think the 3.3v were intentional.

From one of his tweets:
@printrbot: @rosefalk I think you were a benefactor from a major error that I made—- ordered 5V LCD… should have been 3.3V. I’ll make it right.

[REPRAP SQUAD]

I think brook ment the other way around weren't they supposed to be 5v and he ordered 3.3

[ei8htohms]

5V is correct.

Printrbot (@printrbot) tweeted at 10:52pm - 10 Sep 13:

@ei8htohms Laine tells me the correct voltage is 5 volts. Makes sense since my incorrect 3.3V LCD order was overheating. Sorry for the flub. (https://twitter.com/printrbot/status/377625757599952898)