×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Resistance of a pot

Resistance of a pot

Resistance of a pot

(OP)
Iwant to use a pot to "tickle" a Darlington in order to control power to a small (15 watt) motor. Does it matter if the pot is 5 K or 500 K?

RE: Resistance of a pot

1) A darlington is voltage controlled and has insane gain.

2) A pot is generally lousy as they will eventually get intermittent causing all sorts of strange happenings.

3) Your darlington will be running in the linear region if you do this.  This means it's going to have many watts spewing from it!  It will need very serious heat sinking.

4) The proper way to do this is by PWMing the motor.  Turning the transistor either fully ON or fully OFF with a pulse train. The more it's on the more the motor sees.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources