Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Issues caused by short between Source and Gate of IRLZ44N?
#1

While performing a continuity test between Source and Gate pins of IRL244N of an assembled TX Unit v. 2.5 I see current flowing. I supposed this should not happen (?) and I guess I may have damaged the component by applying excessive heat while soldering.

Am I correct to assume this may be the cause of effects I am experiencing such as:
• LEDs being fed ~6v while 12v supply is ON
• FAN being feed 4 and something volts while no 12v source is present
• 7809 regulator having a reading of 4 something volts on the Output side while the board is being powered by USB only

I ask because yesterday I assembled my first unit and while testing (just with a DHT22) I discovered the TX led was not blinking, blown by excessive voltage (I have 510 Ohm resistors applied to R1 and R2). Having searched for a bridge in solder again and again and again and once more with no luck, I am now looking for a problem with components. The Diode seems to be OK.

Activating local debug over serial shows temperature and humidity being read.

The TX led blinks (switches off and on).

Any help/ideas would be much appreciated.


Attached Files Image(s)
       
Reply
#2

First of all, judging by the photos you have done a really nice soldering job.

It's not easy causing damage to the IRL244N just by soldering it.
Maybe, there isn't any major problem. What kind of LED are you using? Some 3mm leds works with very low current and blow easily with 15mA, if you are using this kind of LED, increase R1 and R2 to 2.2K

You can do a small test with your LED's, with just a 9V battery. Connect them with the 510 Ohm resistor you are using, if they work well and don't blow, then they also will work on the TX board.

Quote:I discovered the TX led was not blinking

Quote:The TX led blinks (switches off and on).

This confuses me, there is any mistake here?

Could you please just check, what voltage you have in the output pin of the 7809 when the board is powered by 12V?

Quote:FAN being feed 4 and something volts while no 12v source is present

You are measuring this between the two fan pins, or between the +9V fan pin and GND? If the last case, the reading in normal.

Quote:7809 regulator having a reading of 4 something volts on the Output side while the board is being powered by USB only

This is normal, when the board is being powered by USB only. These voltage comes from the Vin pin on the Arduino.

Reply
#3

(04-04-2015, 20:05)Werk_AG Wrote:  What kind of LED are you using? Some 3mm leds works with very low current and blow easily, with 15mA, if you are using this kind of LED, increase R1 and R2 to 2.2K

I am using this model. Should take 20ma.


Quote:This confuses me, there is any mistake here?

What I mean is: if I apply a multimeter I see the voltage supplied to the led shifting consistent with on-off blinking behavior. Voltage when powered from USB ALONE is OK, something like 2,65 volts. When Powered from 12v I see around 6v.

Quote:Could you please just check, what voltage you have in the output pin of the 7809 when the board is powered by 12V?

9 Volts.

Quote:You are measuring this between the two fan pins, or between the +9V fan pin and GND?
Between the two fan pins.

No temperature sensor connected. Settings modified like this:
byte fanOn_HiTemp = 1000; // RS Fan turn on when outside temperature is >= than this value (ºC)
byte fanOn_LowTemp = 0; // RS Fan turn on when outside temperature is <= than this value (ºC)
byte fanOn_LowWind = 99; // RS Fan turn on when Wind Average is <= than this value (m/s)
Reply
#4

(04-04-2015, 20:24)hvalentim Wrote:  What I mean is: if I apply a multimeter I see the voltage supplied to the led shifting consistent with on-off blinking behavior. Voltage when powered from USB is OK, something like 2,65 volts. When Powered from 12v I see around 6v.

If you see this, and the TX LED is not blinking, maybe it is reversed!
Led anode (big leg) will connect to the pin closer to the edge of the board.

For normal operation, or any test, TX board must be powered from 12V. Don't consider any measure done when it is just powered from the 5V USB.

As an additional info, the LEDS are powered from the 9V rail. They may not blink when the board is powered only by 5V from USB

Reply
#5

(04-04-2015, 20:05)Werk_AG Wrote:  Maybe, there isn't any major problem. (..)
You can do a small test with your LED's, with just a 9V battery(...)

Guess what. You are right. It seems it all derived from my misunderstanding of what I was observing.

While performing your suggested test I came to the conclusion that is was simply a problem with my improvised led connection. It turned out the led never blew in the first place.

I also came to the conclusion that I was figuring the way one should read voltage across a resistor the wrong way. You will only see a drop in voltage when a load is present.

Also, when the DHT22 is present no voltage is feed to the FAN. So I guess the IRLZ44N is doing what is should and it was just a matter of values assumed by the software when all sensors are absent.

So, this serves to prove:

1) that it may be safely said that I am prone to over-complicating matters Smile

2) that my first soldering job ever turned out pretty well and it serves to prove that WeatherDuino can be successfully built by someone starting from a zero knowledge about soldering and electronics

3) that building a weather station may very well end-up being a side effect of a much more interesting endeavour: enlightening oneself on basic electronics.

Now, on to the RX unit...
Reply




Users browsing this thread: 1 Guest(s)