Mosfet frequency output

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bcwilson21
 
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Mosfet frequency output

Post by bcwilson21 »

Is there any way to control the frequency output of a mosfet? It will be controlled by an arduino uno running PWM at the same frequency of 14,372Hz, but will be powered seperatly because of a higher needed current output from the mosfet.

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Franklin97355
 
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Re: Mosfet frequency output

Post by Franklin97355 »

It will be controlled by an arduino uno running PWM at the same frequency of 14,372Hz,
Can you explain how you plan to do that?

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adafruit_support_bill
 
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Re: Mosfet frequency output

Post by adafruit_support_bill »

Is there any way to control the frequency output of a mosfet?
The output frequency is the same as the input frequency - (up to the limits of the device of course.). When the gate is driven high (assuming N-channel), the device conducts.

bcwilson21
 
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Re: Mosfet frequency output

Post by bcwilson21 »

franklin97355 wrote:
It will be controlled by an arduino uno running PWM at the same frequency of 14,372Hz,
Can you explain how you plan to do that?
When you input the PWM code for the arduino there is a section at the beginning that strictly controls the frequency of the pulses, these pulses will in turn switch the mosfet on and off. Heres a link to a youtube video about it; https://www.youtube.com/watch?v=9JXGIeM3BSI
Last edited by bcwilson21 on Mon Jul 14, 2014 10:38 am, edited 1 time in total.

bcwilson21
 
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Re: Mosfet frequency output

Post by bcwilson21 »

adafruit_support_bill wrote:
Is there any way to control the frequency output of a mosfet?
The output frequency is the same as the input frequency - (up to the limits of the device of course.). When the gate is driven high (assuming N-channel), the device conducts.
ok so I understand that it will hold the same frequency as the input source, but is there any way to adjust the sources frequency, the source by the way will just be a standard car battery.

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Franklin97355
 
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Re: Mosfet frequency output

Post by Franklin97355 »

but is there any way to adjust the sources frequency,
You could use a 555 timer circuit to set the frequency.

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Renate
 
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Re: Mosfet frequency output

Post by Renate »

Why do you want to set the frequency?
The frequency of PWM is usually only set roughly because it hardly matters in most applications.
The power source does not play a role.

Yes, you can change the frequency by adjusting the "TOP" value of the counter.
This will reduce the resolution of your signal.

You could also use one of the other counters in the Atmel chip as a prescaler to drive your PWM counter.

bcwilson21
 
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Re: Mosfet frequency output

Post by bcwilson21 »

Renate wrote:Why do you want to set the frequency?
The frequency of PWM is usually only set roughly because it hardly matters in most applications.
The power source does not play a role.

Yes, you can change the frequency by adjusting the "TOP" value of the counter.
This will reduce the resolution of your signal.

You could also use one of the other counters in the Atmel chip as a prescaler to drive your PWM counter.
I need to set the frequency because it will be driving a HHO generator which operates most efficiently at around 14,000 and 43,500Hz. When you say that the power source does not play a roll is that still the case if the Arduino is only being used to switch the mosfet on and off where they have two different power sources Arduino only needing 5V where as the HHO generator will be running at least 30V@5A?

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adafruit_support_bill
 
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Re: Mosfet frequency output

Post by adafruit_support_bill »

I need to set the frequency because it will be driving a HHO generator which operates most efficiently at around 14,000 and 43,500Hz.
This page describes how to set the frequency: http://playground.arduino.cc/Main/TimerPWMCheatsheet
When you say that the power source does not play a roll is that still the case if the Arduino is only being used to switch the mosfet on and off where they have two different power sources Arduino only needing 5V where as the HHO generator will be running at least 30V@5A?
Yes, it is still the case. The gate signal controls the switching. The switching frequency is not affected by the voltage being switched.

bcwilson21
 
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Re: Mosfet frequency output

Post by bcwilson21 »

adafruit_support_bill wrote:
Yes, it is still the case. The gate signal controls the switching. The switching frequency is not affected by the voltage being switched.
So the HHO generator will still receive the same frequency as what the Arduino is putting out without having to change the source frequency?

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adafruit_support_bill
 
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Re: Mosfet frequency output

Post by adafruit_support_bill »

I'm not sure I understand what you are asking. The Arduino IS the source. The PWM frequency you program for the Arduino will be the switching frequency of the MOSFET.

If you toggle a switch every 500mS, the switching frequency is 1Hz - regardles of whether you are switching 1v or 10,000v.

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zener
 
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Re: Mosfet frequency output

Post by zener »

Are you clear on what the definition of frequency is? The battery itself is DC, so its frequency is 0. That won't change. You can have a switch turn on and off at whatever frequency you want. Obviously an Arduino has some limits in this area. Further there are some issues of gate capacitance that could exist at these frequencies if you use a mosfet. You would need a scope and some skill to make sure it is all working correctly. Personally I am skeptical that the frequency will make any practical difference to the hydrolysis process.

bcwilson21
 
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Re: Mosfet frequency output

Post by bcwilson21 »

adafruit_support_bill wrote:I'm not sure I understand what you are asking. The Arduino IS the source. The PWM frequency you program for the Arduino will be the switching frequency of the MOSFET.

If you toggle a switch every 500mS, the switching frequency is 1Hz - regardles of whether you are switching 1v or 10,000v.
This is the basic circuit that im looking at, my question is that since the Positive side of the power is not passing through the arduino in any way, will the frequency from the arduino pwm still apply to the HHO generator (motor in this case).
Attachments
circuit diagram.png
circuit diagram.png (70.96 KiB) Viewed 413 times

bcwilson21
 
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Re: Mosfet frequency output

Post by bcwilson21 »

Zener wrote: Personally I am skeptical that the frequency will make any practical difference to the hydrolysis process.
That's what I have herd from a lot of people, but this isn't normal hydrolysis or electrolysis, where both of these methods require medium current and voltage to split the atoms with brute force, this way uses very high voltage with very low current this is why there is a certain frequency needed.

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adafruit_support_mike
 
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Re: Mosfet frequency output

Post by adafruit_support_mike »

That's the nice thing about the applied sciences: almost all the ideas can be tested and measured.

A gram of experimental data is worth more than a ton of speculation.

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