I am building a dew controller that controls a ni-chrome resistor (dew strap) at about 20?. I use a Smart Two Channel Highside Power Switch FET and I have a small problem with its implementation and i would like some help. I use the ITS621L1 and according to the datasheet http://www.farnell.com/datasheets/85678.pdf i need to have the pins 3 and 2 to the arduino control pin (13 in my case) and arduino GND respectively. On the other hand i need to have pin 4 connected at +12V and pin 1, which is the output, at the positive of my dew strap, the GND of the dew strap is connected at the battery's negative pole. When i turn on the circuit the output voltage to my dew strap is +6V when the arduino signal at pin 3 of the FET is 5 volt, which is the signal to turn on the dew heater. The ST pin, used for diagnostic is 0 so there is something wrong.
According to the truth table when i have the status IN1 = 1 (+5 V), OUT 1 = 1 (+6 V), ST = 0 i have a short circuit at Vbb (output channel) but by checking the solderings i made i have no short circuits at the FET's pins nor at the arduino pin 13, but the FET is getting hot which backs up the case of a short circuit.
Disconnect the device and use a multimeter to actual measure the resistance to ground of the heater output - you
should see 20 ohms if all is well. If there's a short itll be more like <1 ohm
Can you check the wiring step-by-step ?
I can't find a problem with your description of the wiring, but I'm not sure how you have connected all the grounds, and I don't know your sketch.
If you run tests, why not use a led and resistor as a load to test it ? It starts working at 5.0V, so you might also use 5.0V at Vbb during testing.
pin 1, OUT1, output to load. And the other wire of the load to GND.
pin 2, GND. Connect that to the GND of the load, the GND of the power supply and the GND of the Arduino. You should know how to do this, if you have bad connections (for example on a breadboard) the Arduino might turn nuts if the load is turned on.
pin 3, IN1, connect to Arduino output pin. Please upload your sketch.
pin 4, Vbb, Power supply 12V.
pin 5, ST, open collector output. You can connect that with Arduino pin. If you select pinMode( ..., INPUT_PULLUP); it might work.
pin 6, IN2, connect to Arduino output pin. You can use the chip in parallel mode for more power to a single load.
At my circuit i have a DHT22 sensor, a DAllas 18B20 sensor a 20,4 LCD display and 5 buttons at the analog A0 input for menu operations and a buzzer at A1. The circuit worked fine at the breadboard and the test LED i had as the FET worked fine. I admit that i did not have the FET tested at the breadboard to locate this problem earlier since i had to wait for its delivery for over a month and i have transferred the circuit at a Shield on the arduino. Something that thickens the plot is the fact that once i have the FET installed the buttons that perform various operations are sluggish and sometimes unresponsive which means i need to check the connections again. As for the ground connections. All grounds that belong at a component that performs a logic/control operation are connected at the ground pin of the arduino and that ground is the negative pole of the 9V battery i use to supply the circuit. They may not be at the same ground pin but since the arduino provides 3 ground pins a couple of the ground connections are split over those 3 pins. The loads ground is the negative pole the 12V battery i use
The resistance of the pins of the FET are the following with no connection.
pin 1 to 2-> 6,9K. pin 1 to 7 -> 14,08K
pin 2 to 3-> 18,13K pin 2 to 6-> 18K pin 2 to 7->2,18K
all other combinations have infinite resistance
Here is a pic of the circuit. THE CORRECT arduino connections are at the top right of the image and the pin 1 of each component is the top left. Sorry for not having a pc circuit but i needed something to note the circuits as i made sure they were working.
The load's resistance is 18,8? but what caught my attention is the footnote 14 of the truth table that says
Low resistance to Vbb may be detected in the ON-state by the no-load-detection
Is it possible that my load's resistance is so small that the FET thinks it's a short circuit?
