Hello pcf is getting hot when it connect to Arduino's 5V and it doesn't work(i2c finder can not find it).It works when I connect to 3.3V but I don't know why it gets hot when I conect to 5V.
What is connected to the PCF8574. Post a schematic and some photos of the wiring.
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Are you missing the pullup resistors for SDA and SCL?
I used internal pull-up it was still same
When I connect only VDD to 5V and VSS to ground , pcf still getting hot I don't think it is because of pull-up resistors
Are you using a bare chip in a breadboard?
Yes
Can you provide a photo of your circuit?
Post #3 is only a bit of a schematic please supply a full one complete with anything you have got attached to the PCF8574 and the Arduino you are using with what is attached to that.
Does it get hot if only the I2C power and ground are connected?
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it is not getting hot when sda,scl and ground pin is connected but when I connect vdd to 5V , it is getting hot.
I uploaded a photo
red cable -5V
black cable-gnd
blue cable-sda
green cable-scl
You don't show A0-A2 of the 8574 connected to anything.
Try just connecting those 3 pins to ground. You can later decide if you want to pull them up or not to select a different address
it is not because of adress pins. When I dont connect address pin its default adress is 0x26.
My problem is when I connect pcf to 5V it is not working and getting hot.
Now remove the I2C lines but keep the 5V connection.
Still hot?
Never never never, connect anything to an unpowered IC. It will cause lockup and damage the IC.
Looks like you killed this one.
yes still hot but if I connect to 3.3V , it works fine. I don't know why it is getting hot when it 5V I wanted to know that .
As I said you have probably damaged it.
We will appreciate it if you could update the forum if you try another chip and it works; may help someone else down the road.
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