All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > General Electronics Chat

Notices

General Electronics Chat Discussion forum for general chat about anything electronics related, including asking questions about material in the All About Circuits E-book, Worksheets, and Videos.

Reply   Post New Thread
 
Thread Tools Display Modes
  #1  
Old 08-16-2007, 02:54 PM
raidermanz raidermanz is offline
Junior Member
 
Join Date: Aug 2007
Posts: 32
Default limiting DC current

I am new to the electronics world, so please forgive my ignorance, I have a mechanical design background so please respond in "little steps"

I have a heating element which will be powered by a 24vdc power supply, at this time, I am not sure what max current I will be getting, however for this question, let's assume that I have 2A available to the heater. From this same power supply, I would like to power an assortment of low consumption devices. My heater is such that it pulls as much current as I can provide to it when it is below it's rated temperature, and the current draw reduces proportionately as the temperature of the device climbs. I would like to limit the maximum current to the heater to 1.5A.

I am probably missing an obvious solution, but please refer to the first sentence of my post.

Thank you for any and all suggestions
Reply With Quote
  #2  
Old 08-16-2007, 03:02 PM
John Luciani's Avatar
John Luciani John Luciani is offline
Senior Member
 
Join Date: Apr 2007
Location: Massachusetts
Posts: 477
Default

Quote:
Originally Posted by raidermanz View Post
I have a heating element which will be powered by a 24vdc power supply, at this time, I am not sure what max current I will be getting, however for this question, let's assume that I have 2A available to the heater. From this same power supply, I would like to power an assortment of low consumption devices. My heater is such that it pulls as much current as I can provide to it when it is below it's rated temperature, and the current draw reduces proportionately as the temperature of the device climbs. I would like to limit the maximum current to the heater to 1.5A.
Take a look at the TI TL431 datasheet. There is a current limiter circuit and a current
sink circuit. Each circuit consists of a TL431, 2 resistors and q power transistor.
Either circuit will work in your application. Make sure you calculate the power
dissipation of the high current resistor and power transistor.

(* jcl *)

Last edited by hgmjr; 08-16-2007 at 11:51 PM. Reason: Repaired quote box
Reply With Quote
  #3  
Old 08-16-2007, 03:04 PM
raidermanz raidermanz is offline
Junior Member
 
Join Date: Aug 2007
Posts: 32
Default

Thank you very much.
Reply With Quote
  #4  
Old 08-16-2007, 08:58 PM
mrmeval mrmeval is offline
Senior Member
 
Join Date: Jun 2006
Posts: 833
Default

LM317 can be configured as a current limiter.
http://www.national.com/ds/LM/LM117.pdf

And this is interesting, look for current regulator circuits.
http://www.instructables.com/id/ERVL...31U3/?ALLSTEPS

Last edited by mrmeval; 08-16-2007 at 09:01 PM.
Reply With Quote
  #5  
Old 10-16-2008, 09:05 PM
davefromnj davefromnj is offline
New Member
 
Join Date: Oct 2008
Posts: 4
Default

Use a properly rated PTC Thermister in series with the load.
Reply With Quote
Reply   Post New Thread

Tags
,


Related Site Pages
Section Title
Worksheet AC motor control circuits
Worksheet Impedance matching with transformers
Textbook Contactors : Electromechanical Relays
Textbook Vacuum tube audio amplifier : Discrete Semiconductor Circuits


Similar Threads
Thread Thread Starter Forum Replies Last Post
connecting transistors gerases The Projects Forum 69 12-01-2012 12:00 AM
Do I really need a current limiting resistor for charlieplexing? spinnaker Embedded Systems and Microcontrollers 45 11-30-2012 02:51 PM
Calculating Current from DC to AC AutoNub General Electronics Chat 8 11-04-2011 12:50 AM
DC Motor Current Sensing ashish19183 The Projects Forum 10 11-13-2010 12:38 PM
quick check ihaveaquestion Homework Help 23 05-07-2009 09:00 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 01:04 AM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.