Current Controlled Potentiometer???

[nigiri]

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

[BronzeG3]

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

[nigiri]

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.

[Reverend Jones]

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.

[nigiri]

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!