FAQFAQ   GalleryGallery   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in   Forum RSS Feed   Hacked Gadgets Main Site 

Current Controlled Potentiometer???

 
Post new topic   Reply to topic    Hacked Gadgets Forum Index -> Electronic Help
View previous topic :: View next topic  
Author Message
nigiri
Newbie


Joined: 29 Aug 2007
Posts: 3

PostPosted: Wed Aug 29, 2007 2:30 pm    Post subject: Current Controlled Potentiometer??? Reply with quote

Hi there,

Im an artist / programmer getting into electronics as a hobby and this is my first post to the forum. I hope to learn alot from those here!

I may be revealing my inexperience even by asking the question... but Im curious as to whether there is such a things as a Current Controlled variable resistor. Perhaps under another name?

I am using a series of leds controlled by a 4017 decade counter and a 555 timer... and I would like to be able to add an additional "throbbing" effect by varying the impedance between the leds and ground. (perhaps driven by another 555?)

This circuit is to be mounted onto a kite so adding a bunch of resistor /capacitors for each led would be prohibitively bulky (not to mention inelegant)

any suggestions?

Thanks
Back to top
View user's profile Send private message

BronzeG3
HG Master


Joined: 30 Apr 2006
Posts: 134

PostPosted: Wed Aug 29, 2007 6:01 pm    Post subject: Reply with quote

Try looking into mosfets. By changing the voltage applied to the gate of the mosfet, you can control how much current flows through it, and control the brightness of the LED. To get a pulsing action, try looking at a Sine Wave Generator.

This is just something that popped into my head, I have no idea how well it will actually work. Good Luck Very Happy
Back to top
View user's profile Send private message
nigiri
Newbie


Joined: 29 Aug 2007
Posts: 3

PostPosted: Wed Aug 29, 2007 9:39 pm    Post subject: Reply with quote

Thanks for the suggestion! I actually already have a bunch of mosfetts...but was under the (apparently mistaken) impression that they were more like transistors or switches.

I'll definitely look into that!

The wave generator probably wont work for this application as I dont think there is any way to pulse the individual output voltages of the decade counter. Thats why I was looking to control the impedance on the ground side.


Thanks alot.
Back to top
View user's profile Send private message
Reverend Jones
HG Contributor


Joined: 15 Aug 2007
Posts: 39
Location: Jonestown, Guyana

PostPosted: Wed Aug 29, 2007 11:32 pm    Post subject: Reply with quote

The top of the following circuit should be pretty similar to yours. The added LM1458 is a ramp generator circuit used to slowly illuminate and fade the LEDs. In operation, a linear ramping waveform is generated at pin 1 of the LM1458 IC and buffered with the transistor stage. The 22uF capacitor and 47K resistor connected to pin 2 establish the frequency which is about 0.5 Hz. You can make the rate adjustable by using a 100K potentiometer in place of the 47K resistor at pin 2. R-LED sets the maximum current for the LEDs. Adjustments to the point where the LEDs extinguish can be made by altering the resistor value at pin 3 and 6 to ground.


Back to top
View user's profile Send private message
nigiri
Newbie


Joined: 29 Aug 2007
Posts: 3

PostPosted: Thu Aug 30, 2007 3:30 pm    Post subject: Reply with quote

Is that you anton? haha


Thats really funny! That is exactly my circuit! (And here i thought i was so clever and innovative thinking that up) Is that something you already had or did you just sketch it up? In either case I appreciate it. I think this does exactly what I want to do!

Thanks!
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Hacked Gadgets Forum Index -> Electronic Help All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



Powered by phpBB © 2001, 2005 phpBB Group