Hi Everyone,
I’m just scrounging up a few parts and I came across a cheap source of char LCD screens from my favorite electronics surplus company.
I honestly don’t know much about the LCD drivers already built into MBIOs so i can’t to say how much effort would be needed to get these working, but at $4.95 each, the price is right.
Anyone care to venture a guess? It looks like most of the info needed to build a driver is included on the included datasheet.
The price looks excellent, but to me it appears that this display requires “negative contrast voltage” (you’ll find info about that if your search this forum and the Wiki). This is not a problem if you are using a bipolar display. Otherwise, this characteristic can be a nuisance.
I can’t convince myself this is a negative contrast display, so I’ve plunked down $4.95 and I’ll see for myself ;).
I really didn’t need much excuse because I’m going to take advantage of some of the switches they have on there anyways.
I’ve scanned the datasheet from Tianma for my unit and it doesn’t make any mention of a negative display voltage, unlike the one referenced by BG Micro (page 9) in the wiki… That may have just been a note added by BG Micro directly as the original datasheet on Tianma’s for the wiki unit doesn’t carry the negative contrast note either. Humph… It’s not a wide temperature band display, so I may still get lucky. I’ll let you guys know once I find out.
Worse case scenario, I make use of the 9vac from my c64 power supply to feed a small isolated step down transformer and pull my negative V from there. No biggie.
I’ll let you guys know once I find out.
Hi mmalluck, any news on this LCD? I’m considering buying one as well.
Cheers Dude,
madox
I’ve got a few of them in hand, but I haven’t hooked them up yet. I’m just waiting to get my hands on Midibox main board, which i should have later this week. I’ll breadboard together something and let you know what I find this weekend.
I got my core module up and running so I was finally able to test those LCDs. I only smoked-off one LCD in the wire debugging process… go me!
Anyway, the LCDs work fine with the core module as is. No negative voltage is needed. That makes these some of the cheapest 40*2 displays out there. I’ll probably buy a few more before too long. They’re going to come in handy.
Happy to help the community. 
They work fine with the core module as is. No negative voltage is needed.
These are probably some of the cheapest 40*2 displays out there.
Very Cool! Thanks for sharing this find. Ordered two of them and a couple other small parts to raise the order above their (reasonable) $10 minimum order. Sure, it’s not as nice as a white-on-blue Crystalfontz or something, but it’s also 1/10th the price and will work great for testing the mbsid, at the least, when I get to that point. Again, thanks, cheapskates like myself appreciate it 
Hi mmaluck,
That LCD looks really good. I just noticed that Electronic Goldmine has minimum order of $50 + shipping to Australia, where I am located. Anyway, I’m sure there are lots of midiboxers in USA and Canada who will benefit from this part.
I might consider organising with 10+ other Aussies to go in for a bulk purchase, but I’ll have to check if it would work out.
Cheers mate,
Madox
this seems to match the pinout of nebula’s group buy lcd, except the anode/cathode seems to be switched. i can’t verify from where i’m at because it requires chinese text to read the pdf and i can’t do that here. do you think nebula’s lcd pinout is different just because the anode and cathode aren’t on the header? what i’m getting at is this is 1:1 compatible with my ultracore (http://www.midibox.org/forum/index.php/topic,11057.0.html) if i changed those pins around. i’m wondering which way is more standard because that’s the way i wanna do it.
edit: sorry i went ahead and verified this for myself. my core module is gonna be changed and will be compatible with this and a lot of other lcds :).
Hi, thanks for testing those out, I’ve had my eye on them as well.
I note in the datasheet, page 8, that they draw some 413ma of power. Each. That’s 826ma if you use a pair, such as in the SeqV3. I note:
“Restriction: the 7805 gets very hot when it delivers currents above 500 mA, so only core modules without backlit display like MIDIO128, MIDImerger, MIDIfilter should be supplied over this port.” -ucapps, CORE page.
This requires a separate power supply for the displays? I have some 830ma 9VAC supplies for my CORE (hooked one up already, output tests 5V just fine).
mbseq_v3_interconnections.pdf simply shows two LCDs wired directly to the CORE. I’ll suppose that a separate power source must be used for the LCDs, and the CORE only drives other PCBs without LCDs, as stated. I’ve searched the three sites and don’t see an answer. The SEQ page says, regarding hardware requirements:
PSU: Wall adapter (Power supply) 9V / 500 mA.
Smash TV’s excellent site says regarding CORE power:
“500 mA is recommented, especially if a backlit display is used”
http://avishowtech.com/mbhp/mbhp_coreR4d.html
Am I missing something? That has happened to me before. ;D Sorry if this is a newb question and I’m missing an important page of information. I’ve read the “FM262 First DIY Project” thread and will have to build a bipolar supply for the AOUT_NG board I’ll be using with the SEQ, so should I plan ahead and build one with more than 1 ampere for the 5VDC lines (as well as having the 15V bipolar aspect)? Wiring the transformer raw 8V or so source to both the CORE and a separate 5V regulator for the displays? I’ve searched for LCD, wiring LCD, power supply, etc. I’m trying to be good and read everything that I can prior to asking questions. I’d prefer to simply be able to build a unit without having to ask anything, but…
Link to display datasheet:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16610
I note in the datasheet, page 8, that they draw some 413ma of power. Each. That’s 826ma if you use a pair, such as in the SeqV3. I note:
“Restriction: the 7805 gets very hot when it delivers currents above 500 mA, so only core modules without backlit display like MIDIO128, MIDImerger, MIDIfilter should be supplied over this port.” -ucapps, CORE page.
This requires a separate power supply for the displays?
Maybe. Especially as you will have your LED’s on top of that. But you want to use the same transformer. Otherwise, you can use a more powerful regulator, and/or a heatsink (search for that here, you’ll find good info). You’ll have to figure out the maximum that your system could draw. Add up all the LEDs and backlights, add a bit (few hundred at least) for the rest, and add a bit to be safe. There is a 3A version of the 7*05’s (search those too). I personally wouldn’t recommend a completely separate transformer for the LEDs, you could have issues with different grounds…
mbseq_v3_interconnections.pdf simply shows two LCDs wired directly to the CORE. I’ll suppose that a separate power source must be used for the LCDs, and the CORE only drives other PCBs without LCDs, as stated. I’ve searched the three sites and don’t see an answer.
This will work in some cases, and not in others. It really depends on the parts you choose. The schematic you saw is the simple way to do it with non-fancy-schmantzy parts.
It Would probably work in your case too… the 7805 should go up to 1.5A (search it, you’ll find more posts like yours), but if you do that, you will need a heatsink for sure.
The SEQ page says, regarding hardware requirements:
PSU: Wall adapter (Power supply) 9V / 500 mA.
Smash TV’s excellent site says regarding CORE power:
“500 mA is recommented, especially if a backlit display is used”
Am I missing something?
Nope. Your display sucks a lot of juice, and you have 2 of them.
Wiring the transformer raw 8V or so source to both the CORE and a separate 5V regulator for the displays?
8V might be a bit shy. 9-10 is nice, especially if you have a heatsink in case that’s too much. Any more than that is overkill, over 12V is bad.
Just my recommendations, nothing official
Thank you very much for all of your answers! A single 5V 3A regulator sounds just right, used from a single transformer tap for all 5V duties, with 15V bipolar for the AOUT_NG.
