NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Support Forum » LCD will not turn on and Voltage Regulator heats up very quickly

January 20, 2011
by haaser
haaser's Avatar

I am not sure what I have done wrong. As soon as I put power to the board the voltage regulator heats up. I have checked and it is putting 5 volts out. My LCD screen does not do anything. I do not get any black lines and it is completly blank. I had to plug it into a 9 volt adapter as my 9 volt battery is dead. Any help or suggestion would be appreciated.

alt image text

January 21, 2011
by Rick_S
Rick_S's Avatar

It appears you tried to post a photo... but it didn't show. Please try again, so we can see how everything is wired.

Also, in the mean time,

  1. Make sure your 9V adapter has the + lead going to the input of your voltage regulator and the - lead going to your ground rail (same places your battery was connected).
  2. Do not have the USB red wire connected while under external power.
January 21, 2011
by haaser
haaser's Avatar

I have fixed the picture. It should be working now.

I am not sure if I understand your ground suggestion. Maybe the picture will shed some more light on the problem.

January 21, 2011
by Ralphxyz
Ralphxyz's Avatar

Just that led with no resistor will draw a lot of current!! Heating the regulator.

I am surprised it has not burned out.

Ralph

January 21, 2011
by haaser
haaser's Avatar

Ok, I just put the led in there to show that it was on and I will take it out. It was still heating and the LCD was not working without the LED.

January 21, 2011
by tsaavik
tsaavik's Avatar

Can you confirm that your LCD contrast resistor is connected between pins 29 and 27?

I looks like it might be connecting 29 and 28, and that would be bad :D

January 21, 2011
by haaser
haaser's Avatar

I have checked and the LCD contrast resistor is connected between 27 and 29.

January 21, 2011
by hevans
(NerdKits Staff)

hevans's Avatar

Hi Haaser,

Definitely remove the LED from the power rails. Having it there will not let the voltage across the power rails rise above 2.2V and draw a lot of current.

Can you confirm you have the right contrast resistor. It might just be the picture but it looks like black brown orange, which is a 10K resistor instead of a 1K.

I also see a black wire going into your 7805 input pin. Is that black wire connected to the + terminal of the battery?

Humberto

January 21, 2011
by haaser
haaser's Avatar

Yes I changed the resistor and it works now. It is hard to tell the difference between the orange and the red color.

Post a Reply

Please log in to post a reply.

Did you know that a NerdKit can take control of a remote-controlled car? Learn more...