Electronics > Beginners
Fast square wave with arduino and mosfet
<< < (7/10) > >>
ManlishPotato:

--- Quote ---I assume you are powering the circuit by +6V through R1.
--- End quote ---
Oh and this is true, forgot mark it  :)
fourfathom:

--- Quote from: ManlishPotato on September 20, 2019, 07:21:48 pm ---Ok! What do you mean by "lightly couple the FET"?
--- End quote ---

Rather than connect the FET directly to the LC tank, use (perhaps) a small capacitor between the drain and the tank -- much smaller than the tank capacitor.  You would need a resistor from drain to V+ since the tank inductor is no longer providing DC current to the FET.  You do this to reduce the de-tuning effect of the FET drain capacitance, and to reduce the heavy damping of the FET during the "on" state.

What are the values you intend for the tank inductor and capacitor?  The resonant frequency?  How will you be measuring the ringing tank signal frequency?  What kind of accuracy are you trying to get?  All these factors matter.
ManlishPotato:

--- Quote ---Rather than connect the FET directly to the LC tank, use (perhaps) a small capacitor between the drain and the tank -- much smaller than the tank capacitor.  You would need a resistor from drain to V+ since the tank inductor is no longer providing DC current to the FET.  You do this to reduce the de-tuning effect of the FET drain capacitance, and to reduce the heavy damping of the FET during the "on" state.

What are the values you intend for the tank inductor and capacitor?  The resonant frequency?  How will you be measuring the ringing tank signal frequency?  What kind of accuracy are you trying to get?  All these factors matter.
--- End quote ---

Can't check the values right now since i'm not in the office. I'll post an update on Monday once i get a chance to check it out. But i can say that the resonant frequency is or more or less unknown and that's the purpose of the experiment, to use the resonant frequency to calculate the inductance. I'm not really looking for accuracy, only to get in the ballpark of the right value.
Oh and i'm using a digital oscilloscope to view the experiment.
ledtester:
The default circuit for the Falstad simulator shows how to excite a tank with just a switch:

https://www.falstad.com/circuit/

The 10R - 1H - 15 uF side is your tank, the 10R representing the internal resistance of the tank.

The 100R is there to limit the current through the inductor when you hold down the switch.


ManlishPotato:

--- Quote ---The default circuit for the Falstad simulator shows how to excite a tank with just a switch:

https://www.falstad.com/circuit/

The 10R - 1H - 15 uF side is your tank, the 10R representing the internal resistance of the tank.

The 100R is there to limit the current through the inductor when you hold down the switch.
--- End quote ---

That's pretty cool!
I guess what basically i'm suggesting is to replace the button operated switch with a mosfet, and turn it off and on at just the right time to achieve stable oscillation.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod