I used to use a display with a yellow-green backlight and I begun using one with a white backlight. Do I need to make any change?
•Yes. Normally, for the same display model, the consumption of the white backlight is lower than the yellow-green backlight; therefore, you need to change the resistor value which limits the current (customer’s hardware) in order to avoid damaging the backlight.

I have a 16x02 display with normal temperature (0 ~ 50ºC), changed to a model with extended temperature (-20 ~ +70ºC) and I am not being able to make it work. Does the display have a problem?
•No. Probably you are not managing to regulate the contrast so that the image becomes clear; check what’s the necessary voltage to adjust the contrast in the manufacturer’s specification (remembering that that value is the difference between the plug and supplying voltage). If the display doesn´t have a DC/DC converter, you will need to use a source with negative voltage to be able to generate the necessary voltage.

What are a display with a positive image and a display with a negative image??
•A display with a positive image has a light background and the points which form the letters or images are dark (e.g. white background and black letters). The negative display is the inverse (e.g. blackground with white letters).

What are the differences among the reflective, transflective and transmissive displays?
•Reflective: This type of display which doesn´t have a reflector the ambient light which is inserted in the display. Since they do not have a backlight, reflective displays require ambient light to be seen.
•Transflective: This display has a “backlight” which provides light into it from the back or it is lighted by the ambient light which is reflected.
• Transmissive: A type of display which doesn´t have a reflector or transflector on the back part of the glass. A backlight must be used with this type of configuration so that the light lightens the display from the back. The most common is a transmissive one with negative image.

What is a temperature compensation circuit and why is it required?
•The LCD’s operation voltage varies according to the temperature. The operational voltage (contrast voltage or VLCD) must increase as the temperature lowers so that the contrast doesn’t change. Inversely, the operational voltage must decrease as the temperature increases so that the contrast doesn’t change. The “temperature compensation circuit” is the circuit which controls the contrast voltage when there is a variation in the temperature. This circuit can be found in the LCD or in the customer´s hardware.