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Support Forum » Initial Nerdkit project trouble

May 18, 2011
by aibrahim9386
aibrahim9386's Avatar

Hello,

I'm trying to complete the initial nerdkit project and I'm having difficulty with the LCD display.

While testing, I successfully receive 5v out of the regulator, and on the MPU. I've checked the lead going to LCD Pin 2 and that has a constant 5v. I'm not sure what else to check.

I'm going insane trying to figure this out!!!!!

May 18, 2011
by Rick_S
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What problem are you having? Can you take a photo of your setup and post it so we can see your wiring? Are you getting any compile errors? We need more details to help.

Rick

May 18, 2011
by aibrahim9386
aibrahim9386's Avatar

Thanks for responding Rick.

Initially I had the positive of the battery lead connected into row 28 (as instructed) and I could not get it to display so I plugged it into the red rail and the LCD is displaying the messages.

At this moment, the LCD screen is very light. I made sure I connected the 1k resistor (brown, black red) from row 29 to 27 but for some reason it is not as dark as I would like it to be. I ran a test lead from the red and blue rails and I'm getting 7 volts, on the input pin of the regulator I'm getting 6.4v.

What do you think is the issue?

May 18, 2011
by Rick_S
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Disconnect the battery from the red rail before you damage things. The CPU is not designed to run at that voltage and neither is the LCD. NEVER connect the 9V Battery directly to the power rails, it MUST go through the 7805 regulator which will take the battery output from 9V down to 5v. I hope I'm not too late posting this...

Rick

May 19, 2011
by aibrahim9386
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Thanks Rick.

This is what I've done. I've connected the positive lead of the battery to row 28 as instructed and the negative lead to ground, but I am still not getting any power to the LCD. When I connect a test lead from row 28 to the positive lead of the battery, I get 5v on the multimeter.

What gives?

May 19, 2011
by Rick_S
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Is there any way you could post a photo of your setup? That would help a lot.

Rick

May 19, 2011
by Ralphxyz
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aibrahim9386, do you have a multi-meter? What is the voltage across the red and blue rails?

A picture of your breadboard sure would help.

Ralph

May 19, 2011
by hevans
(NerdKits Staff)

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Hi aibrahim9386,

This problem definitely seems to me like a contrast resistor issue to me. Double check that your contrast resistor is a 1K resistor (not a 10K resistor, they are easy to confuse).

Humberto

May 20, 2011
by aibrahim9386
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To Ralph: The voltage across the rails is 7v, and the voltage on the output pin of the regulator is 7v. However, just by simply connecting the regulator alone with the battery, I get the expected 5v.

To Humberto: I'm pretty sure I have the right one, the color code is brown, black red gold.. (1k)...

Here are 2 images:

image 1 image 2

May 20, 2011
by aibrahim9386
aibrahim9386's Avatar

image 1 image 1

May 20, 2011
by Rick_S
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You should not get 7V across the power rails when going through the regulator. If you connect the black lead from your battery to row 29 at the regulator or the blue rail, and the red lead from the battery to row 28 at the regulator, then the output (row30 - and the red rail) should be at 5v. If not, there is definately something wrong.

It's hard to tell from the angle of your photo's. However is the contrast resistor (which looks more like brown black orange in the photo than brown black red) connected between row27 and row29? It appears to go between 27 and 30 which would run power to the contrast connection of the LCD instead of grounding it. This would definately keep the LCD from displaying anything. Also having the wrong resistor would as well. Some oranges on the resistors look pretty red until placed directly beside red.

Also from the photo you appear to have pin 11 of the LCD going to pin 3 instead of 4 on the MCU. (This may just be a camera angle though)

Those are just a few observations,

Rick

May 20, 2011
by aibrahim9386
aibrahim9386's Avatar

Rick,

Is it ok to say, you have an "eye" for things? haha. Your observation of the "orange" instead of "red" was exactly correct. The orange was mistaken for red and that was the problem.

I am officially getting the correct level of contrast, and voltage across the regulator. Thanks for your help!!!!

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