DIY Electronics Message Board
Register  |   |   |  Latest Topics
 
 
 


Reply
  Author   Comment  
Crb3693

Registered:
Posts: 6
Reply with quote  #1 
I think the PIC Flasher k169 kit I have has faulty components in it. I had the test setup with 8 LEDs running/blinking fine and then there was a crackle sound on the board and now it doesn't work anymore. The k169 chip was extremely hot but all of the other components looked fine/no bubbling or blackened parts. I had 9 volt battery running the board and 12v 2.5 amp power supply running the 8 LEDs. I just bought this in the beginning of May, can you replace it or send me replacement parts? I've attached a picture of the kit working fine (before the crackling) if that helps...

Attached Images
Click image for larger version - Name: image.png, Views: 7, Size: 864.63 KB 

Frank

Moderator
Registered:
Posts: 1,889
Reply with quote  #2 
If the LEDs were running/blinking at all indicates to me that the board was fine.

Crackling sounds with electronic equipment usually means a high current pulse through the board, usually as a result of a short circuit somewhere. That usually leads to PCB traces being blown off the board and/or components being charred.

Remove the ICs and check them closely. Also check the PCB for signs of missing traces.

Looking at the photo you may have accidently shorted a couple of the LED leads together which may have caused the problem. There could also be a solder short on the board, especially around the 12V LED supply connection.

You need to do some testing first to try and find the fault.

Connect the 9V battery but not the 12V supply. Check that the 5V regulator is working. You should measure 5V across pins 5 and 14 of the PIC micro.

You can test the 2803 LED driver by removing the PIC and connecting the 9V battery and the 12V supply to power the LEDs. Using a piece of wire connect each input pin of the 2803 (pins 1-8) in turn to +5V (pin 14 of PIC) - the corresponding LEDs should light.

If the 5V supply is fine and the LEDs are working manually then problem is most likely a damaged PIC micro.

The board was working to begin with so don't see why DIY is responsible for any damage caused after that.
Crb3693

Registered:
Posts: 6
Reply with quote  #3 
I get 5 v across pins 5 and 14 of PIC micro. None of the LEDs are working manuallyby connecting 1-8 on 2803 to PIC +5V. Not sure i have the pin layout correct though. I believe you should be liable for faulty parts because the circuit worked fine just sitting there while i took the picture and then it just crackled and stopped blinking lights. There is no short in the led wires, the picture is misleading, one wire is above the other. I am thinking one or both caps under the PIC are bad but i see no charring on them or on any of the resistors. What next?

Chris Brown Jr.
Frank

Moderator
Registered:
Posts: 1,889
Reply with quote  #4 
What makes you think some parts were faulty?

The major reason for kits not working are incorrect parts placement and/or poor soldering. Faulty parts are extremely rare. Not saying it is impossible but HIGHLY unlikely

It seems like you are unsure about the pin layout of the 2803 when testing the LEDs. You really need to make sure that you are doing it right so we can determine if the 2803 chip is damaged or not.

As it stands at present we have no idea just which parts are faulty. Basically it would mean replacing the complete kit, which I think is unreasonable.

I am happy to repair the kit for free if you are willing to send it to me. All I ask is that you pay for return postage. However I am in Australia so the postage costs and time delays need to be taken into account.
Crb3693

Registered:
Posts: 6
Reply with quote  #5 
I've already ordered 2 more of these kits. They should be arriving today or tomorrow. I'd rather you give me tips on how to troubleshoot this board to find the issue. I'm certain its a bad component. I can replace the resistors or the caps from my own inventory but if its either the 2803 chip or the PIC chip, then i don't know where to get a new one that is dependable so I was hoping to get them from you. Do you have a pin layout of the 2803?
Frank

Moderator
Registered:
Posts: 1,889
Reply with quote  #6 
Datasheet for 2803 here - http://www.ozitronics.com/data/uln2803.pdf
Crb3693

Registered:
Posts: 6
Reply with quote  #7 
I had the pin layout right after all. No lights when i connect PIC 5v to each pin 1-8 on the 2803. What can I check next?
Frank

Moderator
Registered:
Posts: 1,889
Reply with quote  #8 
I assume you tested under the following conditions:
1. PIC removed from socket
2. 9V battery connected. This provides the 5V supply to test with - keep checking the 5V supply as the battery will get flat.
3. 12V supply connected to power the LEDs. You need both + and - of this supply connected to the board.

If all the above is correct then seems like the 2803 is damaged.

You can verify that the 12V supply and LEDs are OK by removing the 2803 (power down first) and then connecting a wire between ground and each of the 2803 outputs in turn. They should light. This will also verify that the PCB traces are OK between the 2803 outputs and the LED connections.

You can test the PIC by directly connecting the LEDs to the PIC outputs. This is easy to do - simply remove the 2803 and jumper each input and output together (the pins are directly across from each other). You will also need to only use one LED per output and turned around so the anode is connected to the PIC output. Also the other end of the LED (cathode) connects to ground (not +12V). This is because the PIC output will be high when turning on the LED. The battery may not last that long as it is now powering the LEDs so have a new battery on hand as a backup. Alternatively you could power the kit from the 12V supply you were using for the LEDs.

If the PIC is working then each LED should light as per the DIP switch settings.
Crb3693

Registered:
Posts: 6
Reply with quote  #9 
I figured it out. I jumpered all the outputs together and verified the PIC works. I ran the other tests you suggested and concluded that I have a bad 2803 chip. I happened to receive my other 2 kits today so I tried the 2803 from one of those and it worked. How can I go about getting the bad one I have replaced?
Frank

Moderator
Registered:
Posts: 1,889
Reply with quote  #10 
I will send you a replacement 2803 chip.

I have emailed you direct and included my email address. Please reply with your address details.
Crb3693

Registered:
Posts: 6
Reply with quote  #11 
Done. Thank you!
Frank

Moderator
Registered:
Posts: 1,889
Reply with quote  #12 
Airmail posted yesterday.
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Thank you for visiting.