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Arduino: Nokia LCD & Sensors

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Step 2: Connecting the Nokia3310LCD with joystick shield

So, this is easy, just take the shield (see picture). Plug it in. Load the sample sketch and run it. Right?

Problem 5: Well, not so fast. When I first tried it, the LCD screen was dark and hard to read. When I powered it up with an external 9V battery, it was unreadable.
So I emailed nuelectronics with my problem and of course, got no response.

Solution 1?: I wondered why the LCD was better with USB power than with external power. So I measured the 5V. See picture. It was 4.84V. The power was coming from my PC but it was also going through an unpowered USB hub and 4.84V is acceptable. I measured the same place using a 9V battery connected to the 7805 regulator. The voltage was 5.03V, about what I expected.
The tiny LED in my head blinked. I decided the LCD would be more readable if I dropped the ‘5V’ voltage to the Freeduino and the Nokia LCD. 
My Freeduino has the typical power supply like the schematic. All I had to do was remove the PWR SEL jumper and replace it with a potentiometer (variable resistor) on pins 1 and 2. (or 2 and 3 if using USB power)
So I scrounged a three pin connector with wires on it and solder two wires to a scrounged 200 ohm potentiometer. For those of you not familiar with potentiometers, they are a resistor with a mechanical wiper that can move from 0 ohms to the maximum (200 in this case). Why 200, well it was the smallest resistance I could find. Potentiometers have three leads. You only need two connections, make sure you solder one to the variable pin. See picture. Then plug it in, see next picture.
So this worked pretty good. I could tweak the potentiometer to get a nice display on the screen. BUT. . .

 
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