Keypad works in protoboard but doesn´t in the PCB

Using Arduino Project Guidance
#1

Hey folks. I have google it but didn´t find a reasonable explanation. Here it is:

I have a sketch, with LCD 16x2 and 4x3 keypad and all works perfect in the protoboard.
So for my project I ordered a PCB (a professional one with my design done in easyeda).
I soldered all terminals and assembled the Arduino in the PCB. LCD works great but the Keypad is like crazy.... inputting all kind of number even when I don't touch it...

  • I checked ten times the route, solder, cable, etc... all good.
  • My sketch works great in the protoboard. In same pin of the arduino, etc.

any ideas?
is it any kind of signal interference caused by the pcb or something like that?
looks like the keypad is over sensitive or something like that.

Thanks folks!

#2

And not even a picture? My crystal ball is cloudy today.

First start with the schematic. Verify that everything is connected properly on the schematic.

The first PCB I made, I totally forgot to include the power wires. “Forehead, meet palm!”

#3

I already verifyied the connections…
Attached picture show where the Keypad is connected and the arduino pins (A9~A15).

InkedIMG_3193 (002)_LI.jpg

#4

That's a funny-looking schematic. I could almost think that you took a photo of the PCB.

If you suspect that the PCB is not working, then verify that the PCB matches the schematic. It doesn't matter how pretty it looks if you've shorted two pins together with a track that's incorrect.

#5

Sorry,

That was a picture of the PCB.
Here is attached the Schematic.
Note that GND and +5V are both coming from another PCB through the 15 pin head male.

Again… the keypad is working… but ultra sensitive… If I merely touch it 5 number show up in the LCD.
When I connect the same Arduino, same code, same keypad in the Protoboard, this doens´t happen.

It looks like some interference in the PCB…

Thanks very much for your time!

Placa-1.png
Placa-1.png1181×834 185 KB

#6

Let's see... no bypass capacitors, no mosfet gate resistors, IRF530's not logic rated.

Looks like some very basic but major design errors. Would need to see the board layouts as well, it's likely there are more omissions and mistakes there as well.

#7

Hi,

Note that GND and +5V are both coming from another PCB through the 15 pin head male.

Do you have the gnd from the other PCB connected to the gnd of this PCB.

Your IRF530's are not logic level MOSFETs, yet you are switching them on with 5V gate voltage.

Where are your current limit resistors for each of your LEDs?

Do you have a DMM?

Tom... :slight_smile:
PS.Can you supply a schematic with ALL the pins and connectors connected, instead of having to waste time looking for matching tags.

#8

The current-limit resistors are adjacent to the MEGA symbol. Their values are all overlapping but it looks like they are 330 ohms. LED7-12 don't have resistors but they're obviously plugged into some module which might have the necessary resistors.

Without further information on the keypad, it's impossible to tell if it's properly connected. Pin 8 might have some necessary function (like ground) that isn't shown here.

The numbered pins going to the LCD connector at the top-right are going to be really confusing. 11 goes to 11 but 8 (from A8) goes to 14. I hope that makes sense to you 1 week from now because it doesn't make sense to me right now.

And just as some layout advice: ground symbols always point down. They should never be sideways.

#9

MorganS:
The current-limit resistors are adjacent to the MEGA symbol. Their values are all overlapping but it looks like they are 330 ohms. LED7-12 don’t have resistors but they’re obviously plugged into some module which might have the necessary resistors.

Ahh yes… I just see them now…
Thanks @MorganS
Tom… :o :o :o

#10