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555 Motor Speed Controller

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mike_mike:
Hello, I just built the schematic from the following link on a breadboard and I am getting the following screenshots on the oscilloscope.

This is the link: https://www.multisim.com/content/jcWPXBhUCutR4dmEitXfLg/high-frequency-pwm-with-ne555/open/

The screenshots from the oscilloscope does not look like the screenshots from the simulation, and I don't know why.

I want to use this circuit to control the speed of my Proxxon mini drill. The power source is a 12V/5A SMPS.

Can this problem appear because I build the circuit on a breadboard instead of building the circuit on a PCB ?
What can I do to solve this problem ?

Zero999:
The oscillograms look pretty good to me. Where is the proble? Presumably the output? What are your concerns?

Obviously the 555 will not be able to directly drive the motor directly. A transistor and freewheeling diode will be required.

mike_mike:
The probe is connected to pin 3 and the alligator clip to the gnd.
I though that the output on the oscilloscope should look like the output in the simulation. I built some time ago another 555 pwm controller, which worked at lower frequency, and the output looked like in the simulation, and I though that this should work the same.

I know that the 555 will not be able to directly drive the motor. I will use a mosfet (n-channel). Should I use a gate resistor, for example 100R ?
I will also add a freewheeling diode.

Zero999:
Sorry, I can't see much difference. The oscilloscope waveform looks almost identical to the simulation to me, barring a little noise and over/undershoot, which is to be expected.

Yes, a MOSFET and 100R gate resistor will be fine.

Chriss:
I'm also familiar with Zero999. The scoped signals are pretty good.
Put the 100R to the gate.
When you put the mosfet under load then measure again the driving signal on the 555 pin3 check also the drain signal with scope. Just to be sure does the mosfet is completely closing...

Sent from my GT-I8260 using Tapatalk

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