D.C motor speed controlImportant

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Discussion Overview

The discussion revolves around methods for controlling the speed of D.C. motors, specifically focusing on a method referred to as the "novice method." Participants seek clarification on this method and explore alternative approaches, including PWM (Pulse Width Modulation) and other circuit designs for speed control.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the "novice method" for D.C. motor speed control and requests information on the associated circuit.
  • Another participant suggests that the "novice method" may involve simply reducing the drive voltage, which they believe is not very effective.
  • A different participant mentions that a variable series resistance can be used with a static input DC voltage for simplified control.
  • There is a discussion about the use of PWM as a more accurate method for speed control compared to reducing voltage.
  • One participant warns that higher frequencies in PWM signals can lead to increased eddy currents and overheating of the motor, suggesting that lower frequencies may be preferable.

Areas of Agreement / Disagreement

Participants express varying levels of familiarity with the "novice method," and while there is some consensus on the effectiveness of PWM for speed control, the discussion remains unresolved regarding the specifics and efficacy of the "novice method" and other control strategies.

Contextual Notes

Participants reference different methods and their effectiveness without reaching a consensus on the best approach. The discussion includes assumptions about the definitions and applications of the methods mentioned, which may not be universally agreed upon.

KAS90
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Hello everyone

I have a small question concerning D.C motors speed control. I would like to ask about the "novice method"? I can't seem to find enough information about it, so can anyone just give me a brief explanantion of it? and what is the circuit used for it? otherwise can you give me any other explanation and circuit of any other D.C motor speed control?

Thanks a lot.

I really appreciate it.
 
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KAS90 said:
Hello everyone

I have a small question concerning D.C motors speed control. I would like to ask about the "novice method"? I can't seem to find enough information about it, so can anyone just give me a brief explanantion of it? and what is the circuit used for it? otherwise can you give me any other explanation and circuit of any other D.C motor speed control?

Thanks a lot.

I really appreciate it.

I believe you would usually use PWM of the DC input voltage to control the speed. Maybe the "novice method" is just reducing the drive voltage? That doesn't work very well, so maybe that's why they call it that?
 
berkeman said:
I believe you would usually use PWM of the DC input voltage to control the speed. Maybe the "novice method" is just reducing the drive voltage? That doesn't work very well, so maybe that's why they call it that?

By novice I think he just meant the easy way, in which case just decrease the voltage. If you need accuracy though use PWM.
 
I have never heard of the 'novice method' though like the other posts I feel that it indicates a simplified method of control. With a static input DC voltage, this can be done with a variable series resistance. I have included a PDF document attachment, which explains PWM and H-bridge control of DC motors, though the H-bridge is not the most simple of SCR DC motor control it is the most versatile. Its not great but I hope it is of some use.
 

Attachments

One other point. The higher the frequency of the PWM signal, the more eddy currents will be produced and the hotter the motor will become. In other words, don't use a 40 kHz PWM signal if a 60 Hz PWM signal will suffice.
 
Thanks a lot everyone, I really appreciate it, the information was very helpful..
I think then I will end up using PWM method for my project..
:)
 

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