Need a soft start current source - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th March 2007, 02:59 PM   #1
diyAudio Member
 
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
Default Need a soft start current source

I have a group of HIGH power leds that need about 24v to
run. I would like to turn them on slowley going from off to
500ma over a period of an hour. Any realy simple circuit
ideas ?
  Reply With Quote
Old 16th March 2007, 05:34 PM   #2
diyAudio Member
 
Join Date: Feb 2007
Location: Lake Tahoe, NV
Woody,

The 1 hour progressive turn-on time for your LED driver seems to make inexpensive analog solutions impractical. So, a 5V microP with a DAC output, driving a GND referenced opamp, driving a NPN or N mosfet current source would seem to be simple and cheap.

A LM324 class opamp (cheap, rugged) has common-mode range down to GND so its reference input could be directly driven from the DAC out. The sense resistor on the Em (Source) to GND would be scaled for 500mA at max DAC output voltage. The LM324 could be powered from your LED bulk supply. The programming could be changed to accomodate various turn-on/off strategies, and unused inputs could be programmed for external sensors for additional contol options.

You could use a large variety of cheap PIC processors, or Basic programmed derivatives, should you wish to avoid the obtuse and frustrating initialization for the bare PIC's. My favorite derivative is the PICAXE from the UK (Revolution?). A suitable microP would cost less than $10. One reseller in the USA is phanderson.com. He is a prof. at Towson State in MD and has written a lot of microP applications material on the web in support of his classes using microP's. If you DIY for the programming support hardware; you can get away for less than $10 (assuming you have a PC available). Manuals/Forum/PC Software free on the web from the UK.

Just a thought!
VSR
  Reply With Quote
Old 21st March 2007, 11:05 AM   #3
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
All u need is CD4541, CD4017,Cd4093,LM317 and few transistors.
Make an oscillator from CD4541 of 1 pulse in 7 minutes, connect a CD4017 and use the outputs to control LM317. For details see on the applications of LM317 on national site. Use 4093 to inhibit the counting.
Edit: Use 4093 for power on reset also

Gajanan Phadte
  Reply With Quote
Old 21st March 2007, 11:55 AM   #4
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Default Re: Need a soft start current source

Quote:
Originally posted by woody
I have a group of HIGH power leds that need about 24v to
run. I would like to turn them on slowley going from off to
500ma over a period of an hour. Any realy simple circuit
ideas ?
Just curious: What is your application?
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 22nd March 2007, 04:38 AM   #5
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
I suppose it could be increasing the life of the LEDs
Woody only knows

Gajanan Phadte
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Soft Start Necessary? dtaylo3 Class D 2 26th December 2008 09:05 AM
B+ soft start Gluca Tubes / Valves 2 3rd September 2007 01:04 PM
Need a soft start? maxpou Solid State 19 18th April 2007 09:23 PM
Soft start & Soft Switch circuit: can anybody help? m.parigi Solid State 95 22nd August 2005 03:32 PM


New To Site? Need Help?

All times are GMT. The time now is 05:27 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2