Programmable rheostat?

[blueonblack]

So I'm wanting to add some lights to my new rig, but I want the lights to brighten and dim slowly in a regular (preferably controllable) sequence, rather like breathing. The source of the light doesn't matter, though I assume LED's would be best. The meteor lights sold on Xoxide have this feature, but they also have several extremely irritating patterns that would set off my OCD in the WORST way. Anyone have any ideas on this? Obviously it can be done, but building my own circuitry is beyond me. I had considered a standard rheostat with a geared armature like in an oscillating fan but a prefab circuit sure would be easier!
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VOLVO XC90 SPECIFICATIONS (http://www.ford-wiki.com/wiki/Volvo_XC90)

[nevermind1534]

Look into battery powered Christmas lights with different sequences that you like. You should be able to wire them right up to the PSU.

[Mach]

It's not a hard circuit. Can you solder?

http://www.cpemma.co.uk/555_throbber.html

If not this would be a great project to learn on.

[blueonblack]

It's not a hard circuit. Can you solder?

http://www.cpemma.co.uk/555_throbber.html

If not this would be a great project to learn on.

That's perfect. Yes I can solder but have never built a circuit from scratch. Oh, goody, another first! Thanks!!!
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Iolite vaporizer (http://vaporizer.org/reviews/iolite)

[Mach]

Just for the record, FrozenCPU sells these:

http://www.frozencpu.com/products/4098/lit-134/Top_Shelf_Labs_PCLC-1_PC_LED_Controller.html?tl=g6c77s127

[blueonblack]

Just for the record, FrozenCPU sells these:

http://www.frozencpu.com/products/4098/lit-134/Top_Shelf_Labs_PCLC-1_PC_LED_Controller.html?tl=g6c77s127

Sweet! Thanks!!!!
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Iolite Vaporizer (http://www.vaporshop.com/iolite-vaporizer.html)

[Aud1073cH]

Hey there.

you could save a few bucks by using a simple circuit made with a 555 timer chip for less than $2 - radioshack cat no. 276-1718

go to this site http://home.cogeco.ca/~rpaisley4/LM555.html
(tons of stuff about the 555 timer chip)

scroll down and look at the simple Astable oscillator circuit - there is a calculator to help set the speed you want. It should run on 5V, and output 5V, so you'll need to redo the calculation on the LED resistors.

To get the smooth pulsing (not just flashing) use a capacitor in series with the LED, same polarity (just like adding another LED)


You should have few enough parts that you could make it point-to-point without a proto board, but radioshack has those too if you want to make it nice and neat.

[crazybillybob]

You could also build one of these Pulsing LED (http://www.rabidhardware.net/?id=5) To change how long the LED lights and stays lit just adjust C1 and R4 the Bigger the C1 the longer it takes to light, the larger the R4 the shorter time it stays lit.

Either way you go, I recommend that you build it yourself not only is it cheaper then buying off the shelf, but you learn so much by doing it yourself!!!!


CrazyBillyBob

[Mach]

After lipping off about the 555 circuit, I thought I'd try it myself. Here's the circuit:

http://lh6.ggpht.com/MachModAlbum/SGMiIb053KI/AAAAAAAABY4/GiU0wYEUwQs/s400/IMGP0036.JPG

but it acts more like a flasher than a pulse or throbber circuit. Here's a video that shows what I mean.

pFRFwYFKOVw

I'm changing the setting on variable resistor during filming to alter the pulse duration.

[crenn]

Why use ICs at all? I'll upload a circuit diagram which uses a variable resistor to change the timing of the LED. (It's basically a flip flop circuit)

[Mach]

The circuit was readily available via a google search. Please post something else and I'll give it a try. :up:

[crazybillybob]

The issue you were having with the 555 circuit and you'll have with the flip-flop is that they both generate a square wave out put |-|_|-|_|- the voltage in this waveform goes for 0 to 5V as fast as the 555 can (think...on,off,on,off). What you need is a Ramp (or saw tooth) generator ^^^^^ the voltage in this waveform goes for 0 to 5V more slowly (think, off,low,medium,on,medium,low,off). The pulsing LED circuit posted before (http://www.rabidhardware.net/?id=5) does this with an op amp, the resistor and capacitor in the circuit control the rate and fade of the LED, The Transistor that's in the circuit is there just to driver the LED, without it you couldn't load the circuit much. Most of the parts you can pick up @ radioshack for a few bucks.

If you do some Google searching you can find a saw tooth generating circuit for the 555 (but 555 are normally more costly then the op-amp for this application)

Hope this helps clear up some things!!

CrazyBillyBob

[Aud1073cH]

to smooth out the square, add a capacitor in parallel with the LED.
to change how fast the capacitor charges/discharges, add a resistor in series with the capacitor. This should give you a smoother fade.

[mtekk]

You can get a sawtooth (not a super clean one) from a 555 timer, you just need some capacitors. I built the circuit some time back, then it magically stopped working :dead:. The op-amp and dual op-amp solutions seemed tedious (and messy to do on a bread board). The 555 circuit is dead simple, and works well. That thing that you can buy from FrozenCPU has a Microchip PIC in it, which does offer some flexibility on output sequences, but is really overkill here.


Why use ICs at all? I'll upload a circuit diagram which uses a variable resistor to change the timing of the LED. (It's basically a flip flop circuit)

ICs are smaller, that's why :D. Also, FYI, the 555 has a filp flop in it.

[crazybillybob]

The op-amp and dual op-amp solutions seemed tedious (and messy to do on a bread board). The 555 circuit is dead simple, and works well.

Dude, the Op-Amp Circuit has 1 more part in it then your flashing 555 circuit. If laid out correctly on the breadboard it shouldn't take more then a few minutes to hook up. You could smooth out the 555 flasher with caps, but now you'll have more part (more cost)..
Cernn is correct you could do this with just transistors, resistors, and caps. Just smooth the output of an astablemultivibrator with caps. This would cut down your costs (should be able to make the circuit for $0.50 us).


CrazyBillyBob

[Zeus]

:cgonfused::cgonfused::pics:
Dude, the Op-Amp Circuit has 1 more part in it then your flashing 555 circuit. If laid out correctly on the breadboard it shouldn't take more then a few minutes to hook up. You could smooth out the 555 flasher with caps, but now you'll have more part (more cost)..
Cernn is correct you could do this with just transistors, resistors, and caps. Just smooth the output of an astablemultivibrator with caps. This would cut down your costs (should be able to make the circuit for $0.50 us).


CrazyBillyBob

[crenn]

http://i169.photobucket.com/albums/u209/zs1i/FLIPFLOP.jpg

http://www.sarl.org.za/forum/topic.asp?ARCHIVE=true&TOPIC_ID=1693

To change the speed, change the 10k resistors into variable ones. I think it's possible to replace them with a single resistor, but I can't remember....

[Mach]

CBB - The circuit here (http://www.cpemma.co.uk/555_throbber.html) is supposed to generate a sawtooth. I'm thinking that I did something wrong. Probably the variable resistor. I'll try again.

I bought the parts to build these to do a comparison.

http://www.cpemma.co.uk/555_throbber.html
http://www.cpemma.co.uk/throbber.html
http://www.rabidhardware.net/?id=5

I'm troubleshooting the second throbber now. Probably the variable resistors also. I'll order a couple from mouser.

[crazybillybob]

Mach,
The Circuit from Rabbid, and The Penultimate Led Throbber (Eye Candy4) look like the same Circuit, the eye candy variant throws a variable resistor into the mix to adjust the timings.

The thing with the 555 throbber is that the author has a 10turn variable resistor show (the large blue box with the brass screw head in the photo to the right of the circuit diagram). This would lead me to believe that a small adjustment in resistance greatly effects the output. So you may not get good results if you try and use a normal variable resistor... A little turn of knob means a big change is resistance not what your looking for.

Zeus,
I'm not hosting the circuit diagrams nor did I create them so the polite thing to do is to link to them... Which I did and referenced them in the thread. :think::banana: (the other ways = Copyright infringement and bandwidth leeching.... bad mojo!)


CrazyBillyBob

[Mach]

Thanks CBB, that'll save me the trouble of building the last one. I'll see if radio shack has a 10 turn resistor tomorrow.