# I’m in big big trouble....urgent assistance needed

#### paul_b_78

##### New Member
All was going so well until I forgot to plug the soldering iron into the 5 din socket.
Arrrrrgghh
It started to smoke a little and I’m sure it’s the irlz logic mosfet.
Urgently could do with some assistance

#### rjenkinsgb

##### Well-Known Member
Looking at the schematic in the link, there is no reason at all for the FET or any other part of the power circuit to be damaged by not having the iron connected.

However, the temperature sensor interface is badly designed and will try to put 5V in to a 3.3V pin, by the look of it...
Something like two series silicon diodes across the iron temperature sensor connections may prevent it exceeding a safe level.

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#### augustinetez

##### Active Member
It's an Arduino Nano, they are all 5v pins (other than the 3.3v output).

Looking at the description, I'm guessing it has 24V feed to the supply input of the Nano and when the iron is unplugged, that 24V line has increased and taken out the Nano (24V input is over spec anyway for the Nano).

I would be putting in a seperate 5v supply to power the Nano.

#### paul_b_78

##### New Member
@ Rjenkinsgb
You mention about putting 2 series diodes across the iron temperature sensor, but not mention what value... and can I just add the diodes. Where would I add these diodes into the circuit? Thanks

#### paul_b_78

##### New Member
Also any way I can run a test on my nano without pretty much destroying my built board to check it is giving me correct reading on all outputs.
I am a novice but I am getting better at this.... well apart from frying something of course

#### paul_b_78

##### New Member
Also I followed most of the schematic but mainly worked off the Gerber / PDF drawing using a Perfboard and building the whole circuit from scratch. It’s not the neatest of jobs but I’m fairly confident I followed it exactly the same.
It’s taken me quite a while to do it also as I don’t get to spend all hours each day on it due to other priorities. But I really would like to see if I can fix the issue rather than bin it

#### rjenkinsgb

##### Well-Known Member
OK, I was getting confused which voltage the MCU operated on - I've looked at about 50 different schematics this morning...
The sensor input cannot damage the device.

As Augustinetez says, the 24V supply is too high for that Arduino, unless you have a separate voltage regulator.
The recommended voltage range as just 7 to 12 volts, with an absolute maximum of 20V.

Have you used a buck converter module to reduce the 24V supply, as described in the article?

#### paul_b_78

##### New Member
@ rjenkinsgb
I have a buck converter installed and have it set to about 6.5 volts output as per instructions

#### paul_b_78

##### New Member
Not sure if this helps but this is the setup I have drawn up and followed to the wire.
Unless I’m missing something i.e. an I correct connection then I’m baffled

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#### rjenkinsgb

##### Well-Known Member
The only other thing I can think of is is the display and opamp circuit together are drawing too much current for the arduino 5V reg to handle?
If the display has a built-in backlight it may draw significant power.

#### Musicmanager

##### Active Member

Question : Do those lines in the red circle mean the pins are connected ?

MM

#### paul_b_78

##### New Member
@Music manager
They are connected from the Arduino to a 9 terminal connection point, which then connects to the LCD display, the 3 terminal connection block to the left connects to the POT, and then the other 4 terminal connection (which is down the right side) connects to the I2C in the LCD

#### Musicmanager

##### Active Member
OK .. .. .. .. well I think that's where confusion arises .. .. .. .. mainly due to the Instructable .. .. .. . but partly because using the PCB layout means thinking 'upside down' !

I suggest you compare your board with the printed schematic to check .. .. .. .
I don't think you need the ' 9 terminal connection point ' to the LCD and the I2c connections - either / or ..

MM

#### paul_b_78

##### New Member
@MM
I used the terminal connection as a terminal point for connecting relevant wires (i.e. +5v wires link and GND wires link.
I have an Arduino Nano (but looking at it now it is actually a Nano compatible) so wonder if this is the problem, although the board and connections look identical.
I set the buck converter to 6.5v as that is what it was calling out for but wonder if this could be the problem.

#### paul_b_78

##### New Member
rjenkinsgb and @ MM
I am so confused.. I followed the instructable and many other people managed to get it functioning...
One other thing... I tried to plug my Nano into my PC and the software looks like it hadn’t installed correctly....
Is my Nano fried and can I test it

#### Musicmanager

##### Active Member
I am so confused.. I followed the instructable and many other people managed to get it functioning...
Ok, I'm confused too .. .. but that is mostly because the Instructable is confusing ! For example, the PCB layout you used to make your connections uses a direct connection between the Nano & the LCD; but the schematic uses connection between the Nano and an I2C adaptor; You do not need to use both which is what your sketch suggests you have done. Can you clarify - are you using I2C ??

I tried to plug my Nano into my PC and the software looks like it hadn’t installed correctly....
Which IDE are you using to interface between Nano and PC ? and which software version did you install ?

MM

#### paul_b_78

##### New Member
@music manager
I had a problem accessing my account.

I downloaded Arduino IDE. Never used it before so everything is very new to me.

#### paul_b_78

##### New Member
@MM
I have LCD with I2C.. so does that mean I just need to use the 4 I2C terminal to power up the screen?

#### Musicmanager

##### Active Member
I have LCD with I2C.. so does that mean I just need to use the 4 I2C terminal to power up the screen?
Yes, exactly right .. .. .. .

Have a look here .. Interface I2C 16x2 LCD with Arduino Uno (Just 4 wires) - Arduino Project Hub

Also, I've noticed the two software files on the Instructable are both the same name but only one is intended for use with i2C module; You need to use the one that has ..
C:
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,20,4);
.. .. in the first couple of lines, except change the brackets to read 0x27, 16, 2);

OK ?

#### Musicmanager

##### Active Member
A plan of action .. .. .. .

1. Disconnect LCD pins from Arduino and solder i2c module in place following the Project Hub Sheet.

2. Disconnect pins 3, 10 & A0 from Arduino & use Arduino IDE to load correct sketch. You should then have the LCD working and displaying correctly.

3. Reconnect pins 3, 10 & A0 to give correct displayed readings.

If you're not sure how to use IDE then shout !

MM