Why is so hard to mimic the Knight Rider scanner Effect?

[wuemura]

Hello All!

I've build this "Nite Rider Lights"
http://www.electronics-lab.com/projects/automotive/011/index.html
http://www.electronics-lab.com/forum/index.php?topic=1427.0

Made a few changes in the project to meet my needs, R3 100R, R2 1K, C1 10uF.

By the way, i dont know why i get dragged to projects like this because at the end it will work the same, this one need 7 CI's and a simple CD4017/NE555 do the same effect. So, here is a video of the project working:
http://www.youtube.com/watch?v=OYyYeOvRzm0

My question is, how hard is to use this circuit to make a true Night Rider scanner like this:

http://www.youtube.com/watch?v=-5Ktks-1RjM

 

[audioguru2]

Hi Wellington,
We have three or four Knight Rider scanner circuits in our projects section. Bill Bowden also has some. None use as many as 7 ICs as in this project.

A real Knight Rider fades the lights from one to the next which is automatic when using incandescent fairly high power bulbs. LEDs turn on and off so quickly that they appear to jerk from one to the next.

 

[wuemura]

Hello Audioguru, long time no see!

Yep, i know that, but sometimes you have that feeling that "it might work out". I've done long time ago the basic CD4017/NE555 with some power transistors and light bulbs (i said bulbs not bubs ;D ) used in brake light, and it work like you said, when the light shuts it fades slowly making a nice effect.

What catch the eyes is not that coming and going effect, but the impression that is a devil traped inside that scaner, you know, like an evil bull with red eyes impacient, looking at you, coming and going just waiting the right moment to get you.

Is THAT effect that i want to build and reproduce in a small proportion with led's.

This circuit is not that all bad, comparing with this simple CD4017/NE555 (2CI's) this 7CI's project has a  is very smooth movement as you can see in my video. But, an true Knight Rider scaner has 8 light and not 9 like this one, i think it should be ease to fix this project.

But Audioguru tell me something, to get this effect with led's, it could be done with 47uF or 100uF eletrolitic capacitors right? Connecting then in series to ground so the acumulated energy in the capacitor will discharge slowly and so the led will have a fade effect right?

For thouse that want to build the project i've included in this message the board and schematic.

PS:Rename the extension from .zip to .7z

 

[audioguru2]

To make each LED fade on and off then each LED will need two series current-limiting resistors with a pretty big filter capacitor to ground from the junction of the resistors.

 

[wuemura]

But the effect is only the fade out correct?

 

[audioguru2]

But the effect is only the fade out correct?

No.
I recommend using two series current-limiting resistors for each LED with a capacitor to ground at their junction. Then one resistor charges the capacitor slowly which slowly brightens the LED, and the other resistor isolates the low (off) voltage from the gate so the capacitor slowly discharges into the LED which slowly fades it.

 

[wuemura]

Ok, when i get some free time i will try to mess up a bit more with this project.

Thank you Audioguru!

By the way, you can move the file to the project section for others to build their own board of the project, inside there is a schematic, board design ready to print and the Eagle Project.

 

[AN920]

You can create the optical illusion of smearing by using dither with the leds. This can be done in analog or digital

 

[AN920]

Here is my digital design that includes the smearing effect. The pot sets the sweep rate. I have not tested the circuit in real life but it simulates well.

 

[audioguru2]

Hi AN920,
You made a nice circuit. ;D
Smearing effect? Because it is a fuzzy JPG file type instead of a very clear GIF or PNG file type?

I "enhanced" the JPG smear. A GIF or PNG file type has no smearing.

 

[AN920]

If you use the zoom tool you can see it clearly. Here is GIF version.

I added a screen capture small AVI file of the simulated led movement. It looks a bit jerky because I think my PC is running out of computing speed running the simulation and the capture software but it will give some idea of the operation.

 

[audioguru2]

Thanks AN920,
It is much clearer and is 1/5th the number of bytes.

 

[AN920]

Possible analog version. RV1 sets amount of smear. RV2 full scale cal. RV3 set the sweep rate.

 

[wuemura]

Hey AN920 nice circuit, thank you for your reply.
But come on, don't do this!!!
Let me wrap my hands and hold my self and use my mantra "I dont want to build this!, I dont want to build this!"
;D ;D ;D

Let me ask you something, there is a way to make your circuit work with 8 led's so it will make a true Knight Rider!

I have about 10 circuits builded, i think this will be another one, finger crossed!

 

[AN920]

Just leave out the top and bottom leds making it 8 in total

 

[Omni]

Personally, i would use a string of 12V halogen, the level of crisp bright light is far superior than any LED; my opinion.
However, the above will require a variety of power transistors to sink each lamp.

Halogen is a decent long lasting bulb with excellent illumination:

http://www.radioshack.com/product/index.jsp?productId=2062389&cp=&sr=1&origkw=halogen+lamp&kw=halogen+lamp&parentPage=search

The above is the same bulb used on the 1986 - 1989 Third brake lamp assembly.
Sadly, so many idiots pay $24.00 for this bulb from GM...


-Omni

 

[ante1]

Halogens are not suitable for blinking/flashing due to their very low cold resistance which will limit the lifespan considerably!

 

[Omni]

Let me try to explain this in an easy to understand manner...   :


A halogen lamp uses a tungsten filament that is encased inside a much smaller quartz envelope.
The gas within the envelope is also unique and contains interesting properties.
The latter gas combines with a tungsten vapor which when hot will also combine with the tungsten atoms
as they start to evaporate and redeposite on the filament.
The above is very unique, similar to a recycling process which allows the filament to last longer.

Obviously, flashing a filament is not the perfect solution in comparison to a silicon arrangement.
However, in the event one chooses to select a brighter, more pronounced illumination the halogen will far exceed the
typical filament lamp.

example:

http://tomar.com/products/selfcontsys/police_light.htm



I hope i have made the information above clear enough.   

 

[ante1]

Yes I know very well how a halogen works, thank you! This was not the point here; the point was the limited lifespan a halogen has in the suggested application. Unlike the police light (in the link you provided) the filaments in the knight rider application will have more time to