What problems are in this board?

Thread Starter

booboo

Joined Apr 25, 2015
168
Hi
I'm working on my board and today after assembling some components on it, I ran it and unfortunately sounds like some components burnt out. it's a question to me what cause these problems. this is the schematic:



And PCB:


Also I think one problem is that I have designed two 3v3 LDO for this board to have enough current. I think that was not a good idea. Is there any other problem/mistake in your opinion?
 

wayneh

Joined Sep 9, 2010
16,114
Any idea what might have burnt? Did you breadboard this before building a PCB?

I'd start with divide and conquer. Isolate the various sub-circuits and see if they are still functioning. Check your regulators, check the operation of the iron control circuit. And so on. Look for simple mistakes like reversed components or wrong pinouts. It's often the stupid stuff that is the most difficult to overcome.
 

Thread Starter

booboo

Joined Apr 25, 2015
168
Hi Thanks for reply
after checking the board I found out that the MCU has been died. what would make an MCU dead in my circuit? also the regulator of my LCD module made a big smok when I turned the circuit on for first time. this is my LCD module:



I mean that black and three legs component.
 

mcgyvr

Joined Oct 15, 2009
5,394
deja vu

You already posted about shorts a few weeks ago.. Is this the same problem? Did you fix that problem?..
Why would you assemble "some" components and then attempt to fire it up?
Why don't you tell us which components are faulty or whats not working or something?
Did the sub-circuit components of those faulty components get assembled?

Only soldering "some" components could cause some circuits to not work at all while causing damage to others..
 

Thread Starter

booboo

Joined Apr 25, 2015
168
?
You already posted about shorts a few weeks ago.. Is this the same problem? Did you fix that problem?..
No, I figured it out.
Why would you assemble "some" components and then attempt to fire it up?
yes
Why don't you tell us which components are faulty or whats not working or something?
But I said.:rolleyes: the regulator of my LCD module and the MCU and much more probably regulator on the board.
Did the sub-circuit components of those faulty components get assembled?
I cannot get it. what do you mean "sub-circuit components"?
 

wayneh

Joined Sep 9, 2010
16,114
He means what I suggested earlier - build and check the regulators, build and check some other function. Divide and conquer. Just like you would do if you plugged in a TV and it went poof. You start looking at the power supply and move downstream.
 

Thread Starter

booboo

Joined Apr 25, 2015
168
I thought the probelm is using two 3v3 LDO together then I removed one of those 3v3 supplies from the board and replaced the MCU and LDO with a new one. plugged in and BOOOOOM!:(

There was not any short circuit on the board after replacing( now there is but I'm sure that's not the reason!). there is a problem on the board but I don't know what is it!:(

... build and check some other function...
For example?
... Divide and conquer...
I cannot get this part. What do you mean?
 

wayneh

Joined Sep 9, 2010
16,114
I mean one step at a time. A complex system is very hard to diagnose, but is usually made up of smaller sub-systems. It is very much easier to, for instance, verify that each IC has power to it as expected. Yes? Then start checking the input and output pins of the IC. Sometimes you need to separate the sub-systems completely in order to verify they are working. I think I saw at least one transistor as a switch in your schematic. You can probe to see if that transistor is functioning as you need it to.
 

JohnInTX

Joined Jun 26, 2012
3,814
You don't say what the PN is but your two 3V3 regulators are not pinned like the SOT-223/DPAK stuff I am familiar with. The tab is usually GND. You show GND as where I would expect the input. Miswiring the regulators would account for what you are seeing.
Also not sure about paralleling them.
What is the PN of your regulators? Are they like any of these?
 

Thread Starter

booboo

Joined Apr 25, 2015
168
You don't say what the PN is but your two 3V3 regulators are not pinned like the SOT-223/DPAK stuff I am familiar with. The tab is usually GND. You show GND as where I would expect the input. Miswiring the regulators would account for what you are seeing.
Also not sure about paralleling them.
What is the PN of your regulators? Are they like any of these?
Sorry,
It's AMS1117.

 

pwdixon

Joined Oct 11, 2012
488
I assume you didn't connect the lcd directly on the board connector ie. 1-1, 2-2 etc?

Did you try powering the board without the lcd connected?

Are both of the 3.3V regulator outputs connected directly together?

Did you run any design rule checking on the pcb layout?
 

Thread Starter

booboo

Joined Apr 25, 2015
168
I assume you didn't connect the lcd directly on the board connector ie. 1-1, 2-2 etc?
...
Yes, I didn't.
Did you try powering the board without the lcd connected?
Yes. the last time.
Are both of the 3.3V regulator outputs connected directly together?
Yes, but I think I should to use two diode. because of this:

http://electronics.stackexchange.com/questions/12801/2-voltage-regulator-wired-together-to-produce-higher-amperage-possible

Also the last time I removed one of the LDOs from the board(+ it's capacitors).
Did you run any design rule checking on the pcb layout?
No, How can I it in the Altium?
 
Top