...You don't use PWM to make DAC....

Actually, you can. Look at this. The problem is that it is really slow. Every time you change the pulse width, it takes almost a full second for the output voltage to settle to the new value.

 

Actually, you can. Look at this. The problem is that it is really slow. Every time you change the pulse width, it takes almost a full second for the output voltage to settle to the new value.

My point is that I would use digital pins as inputs to DAC chip if I wanted to generate dc voltage of specific value. They don't have a DAC on the board, they will need to build external DAC circuit.

In the past I tried using Arduino Due DAC. The effing thing was not well implemented by Arduino, it has a known flaw, it only outputs 0.54-2.75 volts, it supposed to output 0-3.3 volts. When my project and me discovered that, is when we fell back to the pwm to generate needed dc voltages. Thank God the pwm worked right.

 

yes "MikeML", for the filter RC the probleme is that.
so "shteii01" i must use a external DAC circuit with a digital pin.
for the power dissipation, I'll take measurements in 10 second maximum, i think that is the solution.

 

...
for the power dissipation, I'll take measurements in 10 second maximum, i think that is the solution.

No, it isn't. If you have more than a 10W panel, you will vaporize your NFET in about 1 second.

 

yes "MikeML", for the filter RC the probleme is that.
so "shteii01" i must use a external DAC circuit with a digital pin.
for the power dissipation, I'll take measurements in 10 second maximum, i think that is the solution.

You have two choices:

Choice 1.
Use internal PWM to generate dc voltages.
It is already built into the Uno board.
Simple.

Choice 2.
Use external DAC chip.
It is not provided by the Uno board. So you have to buy parts, you have to build the DAC circuit.
Less simple.

 

i have a panel which has a MPP 50W.
I made this experience before wih the MOSFET IRFP064N (without arduino).

 

so what can i do?????

What are the voltage and current ratings of your solar cell? If it's a low power type then what you are proposing to do is feasible, but if it's a high power one then you may need to invest in a bunch of FETs and some very expensive heatsinks for them, or use a set of switched power resistors, or abandon the project.

 

i have a low power solar cell.
can i connecte the digital pin of the arduino with the DAC0800?

 

...i have a panel which has a MPP 50W...
i have a low power solar cell...

50 Watts is not low power.

 

I told you it's low powe because i have a power transistor MOSFET "irfp450"(Vds=500v, Ids=14A, puissance=190W).

 

I hope you are paying attention.

In order to dissipate 50W your device must be mounted on a suitable heat sink, regardless of the rating of the device.

I also told you you can use PWM followed by an RC low pass filter.

 

I still haven't heard what the
OP's end goal is - why might you need a variable resistor made from a MOSFET to do something with a 50 watt solar panel?

Once that is described, we might be able to clarify all of the internal posing matches about burning up MOSFETS, using DAC or PWM and/or the need to filter the PWM if it is used.

Once the number of options get so big, it is usually better to step back and clearly define the problem.

 

I told you it's low powe because i have a power transistor MOSFET "irfp450"(Vds=500v, Ids=14A, puissance=190W).

And how big a heat sink do you have your IRFP450 bolted to?

It will have to be at least 100cm by 100cm, mounted vertically, likely with a fan blowing on it...

 

I hope you are paying attention...

I think we may have a language problem. I can speak, because English is not my native language, either...

 

I still haven't heard what the
OP's end goal is - why might you need a variable resistor made from a MOSFET to do something with a 50 watt solar panel?

Once that is described, we might be able to clarify all of the internal posing matches about burning up MOSFETS, using DAC or PWM and/or the need to filter the PWM if it is used.

Once the number of options get so big, it is usually better to step back and clearly define the problem.

The OP wants to make an adjustable resistive load for his solar panel. He wants to study MPPT ( maximum power point tracking).

 

yes i want to study MPPT

 

The OP wants to make an adjustable resistive load for his solar panel. He wants to study MPPT ( maximum power point tracking).

While browsing schematics, I often see PV regulators that are not much more than a hefty MOSFET shunt regulator - you can't turn the sun off, but if you don't divert some of the excess charge current somewhere it boils the battery dry.

Pretty much the same applies as in any other PSU application - if your shunt MOSFET operates in linear mode; you'll need a big heatsink.

 

yes,of course

 

for your load, maybe try making a dummy load like this?

I think it's easier and better than using arduino.

 

maybe, but it's all right
now i trying to connecte the dac 8bits with the arduino