New member
Hello all, I am new to the LCD game and I have a few LCD's i got from work, if I took a few pics of it, can anyone tell me what I need to do to get them to work? And if they are serial based. There is more than 9 pins, like 12 i think, I dont have them here. And is the new Crystal Control program going to support Windows Media player? Is there any that does? Thanks. - Nick
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.

CF Tech

Looks like a pretty standard 40x4 character LCD.

Should be able to drive it with CrystalControl through the parallel port (test with CFAH_WinTest first).

Take a look on our links page for other software too.


New member
ok cool, I need a little help from someone if they can. I know it was given without support so if someone thats not a mod that can help me that would be great.

In the instructions (the link above), it says to find the resistor value which would be R = (5 - volts) / current. I found the current in the manual found here . I am not sure what value to use for the volts. I tried 4.5 but got a value of 0. If someone can help, that would be great. Thanks. - Nick
The data sheet gives 4.2 volts as the LED voltage, and 600 mA typical (yow, what a power hog!).

Rlim = 5.0 - 4.2 / 0.6 = 1.3333 ohms.

Resistor power = 0.8 * 0.6 = 0.48 watts, so use a 1 watt resistor.

How did you get a value of zero???
The resistor value you need is (ideally) 1.333 ohms, but you could use anything from 1.0 to 5 ohms. Don't go lower than 0.9 ohm, or the backlight may run hot (and suffer short lifetime). If you go more than 5 ohms, the backlight will be dimmer than normal but maybe still usable.

The 1200 mA you saw is the ABSOLUTE max rating (which you would get with a 0.666 ohm resistor). The normal range of operating current is spec'd at 140 mA to 900 mA. I would advise staying within that range.


New member
thanks alot for all your help. One more thing, it says to use a 100ohm trimpot. for the backlight. I cant find one, I only find 100k and bigger. Any suggestions? - N
backlight control

First off, you need to put a 1 ohm resistor in series with your trimpot, else when you turn the pot to the high end, your backlight will go up in smoke, poof. You can get a 1 ohm 1W resistor at Digi-key:

Next, you don't say any details about the pot. A trimpot implies a board-mount, screwdriver-adjust, device, and you can get them in 1-turn, 3-turn, 5-turn, 10-turn, and 20-turn. You will still need a 1 watt power rating so you don't fry it when its turned near the high end. 1 watt trimpots are not too common, but you can get them at Digi-key too. Or you could choose a panel mount pot with a shaft, these are much more commonly available in a 1 watt rating. Then you get to choose the type: wirewound, cermet, carbon comp., etc. So, if you decide on the detail, I can steer you to a part #, or you can search the site yourself. Pots will cost anywhere from $5 to $50, depending on type.


New member
i have the resistors already, i was just looking for the trip pot and thanks for your help again. I dont care what kind it is, just the eaiest ti find and cheapest to buy.