# Please explain me the heating principle

Joined May 11, 2018
158
Hello i have a heater that is 10W rating , that is all i know about the heater ,

I also know that it is a filament , which i guess that i can not connect on power supply directly , i have to connect it in series with a resistor to atleast heat , i connected it in series with a 1k resistor , and the power supply is drawing 10v and 6ma .

My question is how much time is it going to take to heat , and what can i do to make it heat more time .

should i increase the voltage ? or probably the heater is broken and i don't know ....

Thanks

#### Dodgydave

Joined Jun 22, 2012
9,956
10W at 10V is 1amp, you are drawing 6mA at 10V , that's 60mW!! ,

Take the resistor out and connect it directly to the PSU at it's correct voltage.

#### BobTPH

Joined Jun 5, 2013
3,333
Do you know the voltage rating if the heater? If so, connect that voltage or less directly to it.

If you dont know it, and you have a lab supply, you could connect it with the voltage set to minimum, then, monitoring the voltage and current, Raise the voltage slowly until the product (V • A) is equal to 10.

Bob

#### jpanhalt

Joined Jan 18, 2008
11,088

#### BobTPH

Joined Jun 5, 2013
3,333
Actually, looking at your numbers again, I think this heater is designed for 120V.

Your 6ma with a 1K resistor is 666 Ohms. That would be 20W at 120V, but the resistance would go up as it heats, so 10W sounds about right.

Bob

Joined May 11, 2018
158
I did it it is now working. i just took the resistor off and put it directly and changed the voltage and it is now working

Joined May 11, 2018
158
Can you help me with this one now

I am driving the same heater 3v at 1.3 A and the arduino is a power MOSFET Of IRFZ0.

But it's not working it's only heating the mosfet but the heater is not heating , it looks like something is blocking the current to flow through because , without the arduino the heater heating at 3v 3Amps

thanks

#### bertus

Joined Apr 5, 2008
21,371
Hello,

Do you mean that you want to drive the heater with the 2N1711?
The heater has a stated current of 1.3 A, the 2N1711 can only drive 1 A (absolute maximum).
Better use a good logic gate mosfet.

Bertus

Joined May 11, 2018
158
Hello,

Do you mean that you want to drive the heater with the 2N1711?
The heater has a stated current of 1.3 A, the 2N1711 can only drive 1 A (absolute maximum).
Better use a good logic gate mosfet.
No i am using a IRFZ20 , but that is a nice point of view how do you see the current rating of a MOSFET
from this sheet(https://www.vishay.com/docs/91340/sihfz20.pdf) , it says drain current is 10A. I m not sure if i am correct

BUt is the wiring correct or i need to put a resistor somewhere ?

Last edited by a moderator:

#### bertus

Joined Apr 5, 2008
21,371
Hello,

Better change the IRFZ20 to a IRLZ24.
It can well be that the IRFZ20 will not be fully on at the voltage given by the Arduino.
The IRLZ24 needs less gate voltage to be fully on.

Bertus

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Joined May 11, 2018
158
Hello,

Better change the IRFZ20 to a IRLZ24.
It can well be that the IRFZ20 will not be fully on at the voltage given by the Arduino.
The IRLZ24 needs less gate voltage to be fully on.

Bertus
Yeah but i have an irfz20 and it has a Cgs threshold of 4v and min the of 2 .

#### bertus

Joined Apr 5, 2008
21,371
Hello,

What is the output voltage of the Arduino?

The threshold voltage is the voltage where the current is about 250 μA.

You want a much higher current.

The IRLZ24 has a much lower threshold voltage:

Bertus

Joined May 11, 2018
158
Hello,

What is the output voltage of the Arduino?

The threshold voltage is the voltage where the current is about 250 μA.

View attachment 210988

You want a much higher current.

The IRLZ24 has a much lower threshold voltage:

View attachment 210989

Bertus
the output voltage of the arduino is 5v

#### bertus

Joined Apr 5, 2008
21,371
Hello,

The IRFZ20 can carry just over 2 A at Vgs = 5 Volts.
You are driving it at its limits, as the output of the Arduino will likely just a little bit lower as 5 Volts:

The IRLZ24 can carry 17 A at Vgs = 5 Volts.

Bertus

#### bertus

Joined Apr 5, 2008
21,371
Hello,

What is the supply voltage of the Arduino?
The absolute maximum voltage for the ATmega328 that is used in the Arduino is 5.5 Volts.

Bertus

Joined May 11, 2018
158
Hello,

The IRFZ20 can carry just over 2 A at Vgs = 5 Volts.
You are driving it at its limits, as the output of the Arduino will likely just a little bit lower as 5 Volts:

View attachment 210996

The IRLZ24 can carry 17 A at Vgs = 5 Volts.

Bertus
how do you determine that the voltage is 5v 2A . I would say it's 10 A .
But how do you read that

Joined May 11, 2018
158
Hello,

What is the supply voltage of the Arduino?
The absolute maximum voltage for the ATmega328 that is used in the Arduino is 5.5 Volts.

Bertus
yes its using 5.1v

#### bertus

Joined Apr 5, 2008
21,371
Hello,

There is a saturation graph in the datasheet:

Bertus

#### Audioguru again

Joined Oct 21, 2019
3,208
The curves on a datasheet are only for a Mosfet with typical spec's.
Where can you buy a Mosfet that has a typical saturation characteristic? Many of them conduct much less current when the Vgs is 5V. It is guaranteed to conduct only 0.00025A when its Vgs is 4V (its threshold voltage).