In another post, the user 'dfrobot' (presumably somebody from DFRobot), mentioned that the new version of the DFRobot LCD shield does enable pin 10 to control the brightness. I tested the board I had ordered from Robotshop.com on May 31st, and setting pin 10 via PWM to 0..255 does control the brightness level.
I have been done the mod adding a Diode (IN5819) how you can see in the schematic (I have marked green the new diode in the graphic) . Now I have a new issue with the brightness wich have been decreased...
Quote from: CarlosGz on Jul 16, 2012, 10:02 pmI have been done the mod adding a Diode (IN5819) how you can see in the schematic (I have marked green the new diode in the graphic) . Now I have a new issue with the brightness wich have been decreased...That is because the diode does not go in series with the pullup resistor to the base of thetransistor but in series with the D10 to connection of the base of the transistor.--- bill
Almost, The diode is flipped/reversed. (I think you would have quickly figured it out)The diode is used to isolate D10 from the circuit when D10 is high.The pullup resistor is used to turn on the transistor.The backlight will be on if D10 is input or HIGH.Setting D10 to low turns off the backlight.The diode allows D10 to yank the pullup down to gnd to turn off the transistor when D10 is low.It works but really isn't a good design, I wouldn't design a circuit like this.I did it this way because I couldn't easily desolder the LCD on the shield I had to replacethe transistor with an FET. (The transistor was underneath the soldered LCD module)--- bill
Briefly (and I mean just a brief touch) connect the wire from D10 to Vcc.
Thank you dweston and bperrybap I just noticed that the product page says"Do not use Pin 10 while this shield is connected" http://www.robotshop.com/productinfo.aspx?pc=RB-Dfr-07&lang=en-USI do not remember that statement when I ordered it impressive if they have responded to this info so quickly
It looks like robotshop is not dfrobot.No warning here, and the schematic has not changed...Bummer...