So I have ordered the first of the two listed LCD displays and saw some of the posts of other builders where they needed to position the LCD flippy-flopped and sometimes needed to out resistors so as to not do any frying of things. This is the part I ordered, http://www.mouser.com/Search/m_ProductDetail.aspx?Newhaven-Display/NHD-0240AZ-FL-YBW/&qs=3vk7fz9CmNxRmMV%2bzNmvFg== I spose I just want to know: 1) what it is that I need to do to not jack this up and 2) what are the technical reasons for me to do these things. I really like knowing “why”
Nothing? Not even to tell me to read somewhere else? Don’t make me derail the “Political” thread with a link to this one.
Right, no idea on that particular display, but it seems like it needs a rather low supply current for the LED (if my datasheet reading memory serves me right).
I do however know the why :
LCD displays like this one need a backlight, and usually that is provided in the form of a piece of plexi underneath the actual display, with some silver tape around the edges(to keep the light in, and to boost the apparent brightness)+a LED in one of the ends. This LED is what determines the background color of your LCD, and if it burns out you’re gonna have a bit of a hard time replacing it(should be possible, but not the greatest of ideas). Like all LEDs before it this LED needs a certain current+voltage to light up, but if it gets too much of said current+voltage it burns out, thereby rendering it inoperable. If this happens, your LCD will still work, but it will be very hard to read in anything but direct sunlight. Since most of us don’t have a miniature sun in our studio, we prefer LEDs that work
What I’m guessing is being alluded to is that the default resistor for LED current is letting too much current trough for this particular LED, which would kill the LED fairly quickly (usually in the millisecond range)…
Thanks, I’m trying to get comfortable with power and its relationship to components. I’ll do some serious googling tomorrow. I know there was a thread in which an optrex display is the center of discussion and I remember the milliseconds comment (maybe from you). It had a decent amount of information of how to calculate what resistor I would need based on data sheet information. Do threads ever get removed from here? I’ve been doing some serious searching of that thread with little luck.
Threads are usually not removed, so it was probably under some obscure title
Googles sitesearch may be more helpful, +a google search for LED calculator (there are a LOT of them around)…
If too much current flows through a LED, it won’t handle it. The resistor in series with a LED controls how much current flows through it, and ultimately defines the brightness of the LED.
Some LCD manufacturers consider that it is the responsibility of the developer to set it up; while some other manufacturers build this LED into the LCD or use their own LED driving circuit which is directly powered by +5V.
alright guys, I’m pretty much done with Ambika but I’m still a little uncomfortable installing the LCD because I don’t much feel like frying it… 763-NHD-0240AZ-FLYBW is the part number and I’ve attached the Specs given on the data sheet to find an appropriate resistor (if any are needed). If I were positive on what the forward voltage and other normal specs were I’d Ohm’s law it and not bother you folks. But either my knowledge or newhaven’s data sheet is poop. I’ve opened all the data sheets for the alternative lcd’s but haven’t found common reference points. Please enlighten me so I can jam out.
I used that newhaven part on an midibox build, they work fine and look sharp. If you’re not sure about the resistor, get a 1K trimmer and dial it in
I’m running out of the door now for one. You sir, have earned yourself a beer.
Don’t turn the trimmer fully down to ZERO ohm!
Is the best way to find out what it is set to right out the package to solder the trimmer and test before inserting display at a particular point?
you can measure it before putting it in, they usually come set in the middle
Backlight supply voltage = 5.0V ; so it looks like it has a built-in current limiting resistor.
I appreciate it. Now I have an extra trimmer floating about.
@pinchenettes: I thought so but doubt my ideas in this field. The ambika has been a really enjoyable build; the six voice cards made for a very peaceful learning opportunity/time spender. Sounds up this week… Hopefully
you can never have enough trimmers floating around highly useful devices. To be honest, I dont recall how the backlight behaved with those displays but I do remember that they looked good. Transflective displays are pretty cool since they are designed to work in all light conditions (think LCD displays in your car) and the newhaven ones are crisp and fast
Yeah I slapped it on tonight but I’m a few beers in and don’t really want to screw anything up so I stopped. I’ll tackle more in the morning. Unfortunately, my ground cable on my multimeter felt it should rest on my iron. If i can see the cabling inside, think I should get some new ones? It didn’t detect any shorts on the board without power but it was doing crazy fluctuations on volts just being in the air. Thanks guys, I’d been holding off with the LCD as long as I could
You haven’t wasted your money with the extra trimmer-you can still install it anyway and use it to dim the LCD backlight if you find it too bright…