Jump to content
Electronics-Lab.com Community

Night rider scanner


Recommended Posts

This redrawn simplfied circiut from my collection was drawn ina special way by circiut maker and retraced in black to highlight it enougth to come out when photographed, for posting, ill post another similiar one soon and because it uses more of the 4017 decade counter pins, it allso makes a good decade counter testor.

by Steven (received via e-mail)

Link to comment
Share on other sites

Mixos,
Steven's circuit is not a knightrider, it is a chaser that misses a few steps. We have discussed knightriders and chasers recently in this site at: Electronic Projects Design/Ideas, "LED Flasher (very interesting)".
In Steven's circuit, R5, the LED current limiting resistor, is not needed because the 4017 outputs have built-in current limiting at about 9mA with an 8.3V supply.
In Steven's circuit, the transistors in the multivibrator have their base-emitter junction driven beyond their 7V maximum rating which causes damage to them.
A good knightrider project is in our site's project section here:
http://www.electronics-lab.com/projects/motor_light/035/index.html

Link to comment
Share on other sites

In order to avoid continuing confusion about knightrider/chaser, for those who have not seen the American TV show, is it possible to include the animated GIF:

into the project article, above?

Is it also possible to remove the phrase,"Knightrider" from the Projects Index for the chaser circuit:
http://www.electronics-lab.com/projects/motor_light/028/index.html

Link to comment
Share on other sites

But 5 chips (the 5th is a 5V regulator) just to flash leds?


Audioguru, you have a point there, i was thinking the same thing when i was first designing the thing. Wish the 74154 had had some type of F-F and up/dn counter built-in. I had thought about using a 4017 but it would only give me sequencing in one direction with 10 LEDs. Do you know of a stand alone IC that can do dual sequencing of 16 LEDs or more ?

Do you have a picture of the prototype?


Sorry MP, no i dont. I gave the board to my bro, seams he used it in a holloween costume for light effects. But I have the ExpressPC board layout on a floppy somewhere, i'll post it here if and when i find it.


Link to comment
Share on other sites

Nettron,
We have a 6-LED knightrider circuit in our projects section. The 4017 counts forward lighting LEDs 0-5, and diode gates are used to light those LEDs in reverse order while the 4017 continues its count of 6-9. From a 9V battery, the 4017's outputs are current-limited to about 11mA, so a current-limiting resistor is not needed. The project is here:
http://www.electronics-lab.com/projects/motor_light/035/index.html

An LM3914 dot/bar-graph chip lights 10 LEDs sequentially in both directions when fed with a dual-opamp triangle-wave generator. The LM3914 can be cascaded to allow umpteen-dozen LEDs, but the set-up adjustment will be tricky after maybe 50 LEDs.
A D-A converter would feed cascaded LM3914s beautifully.

Link to comment
Share on other sites

We have a 6-LED knightrider circuit in our projects section.


Yes i was looking at that earlier, nice little compact design. Its also available from Doctronics in kit form here:

http://www.doctronics.co.uk/kits.htm#chaser

Unfortunately wasnt enough LEDs for my app.

An LM3914 dot/bar-graph chip lights 10 LEDs sequentially in both directions when fed with a dual-opamp triangle-wave generator.


Yep had looked into that as well, was thinking about taking the ramping voltage right off the timing capacitor on a 555 astable and use the LM3914 in dot mode. only problem was i didnt have a 3914 handy so tried the nuts-n-bolts route using comparators (LM339), had lots of those. But the design became too complex and just plain overkill, so later dropped the idea (violated the KISS rule). But something worth looking into.


Link to comment
Share on other sites

Nettron,
Don't use the ramping voltage of a 555's timing capacitor to drive an LM3914 because it is not linear with time. It would start counting the LEDs quickly, then slow down when nearing each end. The integrator output of a dual-opamp triangle-wave generator is perfectly linear.

Link to comment
Share on other sites

Don't use the ramping voltage of a 555's timing capacitor to drive an LM3914 because it is not linear with time.


Remember i didnt have a LM3914 and was using LM339 comparator IC's. The idea i had in mind to solve the non-linearity problem, without adding another IC , was two-fold: 1. use different amounts of feedback around each comparators to "pull" the input voltage over threshold at appropriate timing intervals, 2. use a different reference voltage for each comparator. Yeah i know, it sounds ugly but that was 2 years ago and i havent looked at it since.

Have you considered distorting the ramp so the LEDs slow down at each end like a pendulum?


Hmm...interesting,hadnt thought of that. AG maybe you should post a design based on that idea,I for one would really like to see something original.

Link to comment
Share on other sites

The exponential charge/discharge of a 555's timing capacitor IS like a pendulum! But the effect is reduced by the 555's lack of full charge and discharge (1/3 of +V to 2/3 of +V).
So maybe it would be best to low-pass filter a square-wave in order to obtain an alternating voltage that changes very quickly at the beginning and very slow at the end.
What do you think about that?
How many LEDs?

Link to comment
Share on other sites

Appearently not all that original .

http://www.eki.com/product.asp?number=2009

Maybe add a few more rows of LEDs, with different numbers of LEDs in each row, to simulate the "string" with the longest row representing the bobbin at the end. Maybe this belongs in another thread ?

So maybe it would be best to low-pass filter a square-wave in order to obtain an alternating voltage that changes very quickly at the beginning and very slow at the end.


Appears do-able. Another option could be to build a circuit based on the internal window comparator on the 555 timer IC but with independent control over the charge/discharge rate and window reference voltages ( Vtrip upper/Vtrip lower).



Link to comment
Share on other sites

Nettron,
Eki aren't using 18-pin LM3914s but are probably using the same circuit that you have, except using CMOS instead of your TTL.
A quick check of Kinetics shows that a pendulum doesn't swing exponentially, but more like a sine-wave, since its inertia starts it swinging slowly, the same way that it ends when it runs out of momentum.
What happened to KISS? You sound like an LED salesman. Those LEDs will be coming out of our ears!

Link to comment
Share on other sites

Eki aren't using 18-pin LM3914s but are probably using the same circuit that you have, except using CMOS instead of your TTL.


I mean the pendulum concept not the type of IC's used, although cmos would be better when it comes to power consumption, especially if we're talking portability.

What happened to KISS?


Taking a backseat at the moment i guess, im sure it can be refined, perhaps use a sinewave oscillator to drive a 3914('s). Making it more analog rather than digital would be something i would be even more interested in.

You sound like an LED salesman. Those LEDs will be coming out of our ears!


..and for todays special, 2 bags of LEDs for the price of 1 ;D yeah i can imagine a salesman's delight at someone designing a commercial circuit/kit with that many LEDs. Just more eye candy not really necessary
.




Link to comment
Share on other sites

Nettron,
I mentioned CMOS because Eki's kit doesn't appear to have LED current-limiting resistors. CMOS outputs current-limit at about 11mA from a 9V battery.
I agree that linear will look better than logic, because the LM3914 "blends" between adjacent outputs, while logic will go: jerk, jerk, jerk, etc.

Ldanielrosa,
Microcontroller use also is not very original. I can purchase this circuit from my local car-accessory store and have a choice of LED colours. The product has a microcontroller chip under a blob of black epoxy, and the LEDs are surface-mount. It is supposed to make your car appear to have an expensive (and noisy) security system.
Cell-phone covers also have many blinking LEDs.

Link to comment
Share on other sites

I would tend to agree with LDanielRosa. A microprocessor would be a good way to go. As far as this not being original: Obviously a statement from one who does not program. That would be like saying that there are a lot of op amp circuits, so using one in a new design is not original. The code for a microprocessor will give you complete control of the LEDs in any sequence, pattern, brightness, etc. The program can be as original as you need for it to be - because you are writing it.

MP

Link to comment
Share on other sites

A microprocessor would be a good way to go. As far as this not being original: Obviously a statement from one who does not program


I assume by "microprocessor" we mean a microcontroller, yes ive seen that suggested on other forums. A controller such as the PIC can simulate in software just about any logic circuit. I agree this would be a good option if the IC count and "wiring" become too great, but like MP mentioned thats assuming one is comfortable with programming.

This has somewhat jogged my memory ( excuse the coming pun) ,managed to dig up an old schemy of a circuit i once used for proramming SRAM memory IC's. Its an option to using a micro and for programming eliterates, its programmed one bit at a time via a non-encoded keypad.


http://www.geocities.com/nettron1000/2816SRAM.html

Only drawback is that the info will be lost when power is disconnected. A way around this problem would be to use EEPROM's.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
  • Create New...