Adjusting components for a new Vcc+ ? - Light Chaser

Discussion in 'General Electronics Chat' started by Landwand, Dec 6, 2010.

  1. Landwand

    Thread Starter New Member

    Dec 6, 2010
    Hello everyone,

    I've Googled the issue and have stumbled into this forum! Please be kind.

    My issue:

    I can find circuits easily enough online, but they range anywhere from 1.5 V - 12V Vcc. If I wanted that circuit, but I am using a different power supply (5V USB adaptor in my case) how would I come about changing the components? I remember Ohm's law just barely, but it becomes very difficult, if not impossible for me to decipher and re-engineer after leaving electronics for so long.

    What I want:

    I'm a model-maker looking to work with a few blinkie lights and sounds. Currently, I'm looking to make a LED Chaser circuit, flashers and strobes. Pretty easy fare, as I remember doing this stuff in Grade 10.


    I took electronics in high school, from 9 - 12, but that was many years ago. I feel pretty old now... in any case, unfortunately, I threw out all of my notes so I have to go from what I remember.

    One of my friends suggested that I go to a microcontroller, but the set up is very confusing for me, and it seems to be a needless headache and expense at this time. He says that MCs are very flexible and can do various interesting effects for my projects -- but still.

    I do not have a brick-and-mortar store within driving distance, so I have to turn to the Internet for components. I'm stumped right now, as I have no idea which components to order as I don't have a schematic to work from right now. I need caps, resistors, LEDs, 555s and maybe a 4017 chip or two. But their values; that I have no idea.

    Please give me your feedback!
  2. Wendy


    Mar 24, 2008
    One of the key problems is you must know Ohm's Law. This is to allow you to know how much current you will have for a given situation. It is a necessary foundation for all else.

    The second thing is you need to learn LEDs and their limitations. They are truly great devices, but they have boatloads of things you much understand about them, one of which is (what else?) Ohm's Law.

    I have written a tutorial for beginners on LEDs and more advanced circuitry. Pay attention to chapter one and the part of chapter two that deals with resistors. Get this down and you are well on the way.

    LEDs, 555s, Flashers, and Light Chasers

    Bill's Index

    5V is just enough to light one or two LEDs in a chain, no more.

    Microcontrollers are another world. They are worth learning, but you need to get the basics down first. They replace large reams of circuitry with programming. Programming is hard work, but unlike components, it doesn't take gobs of cash once you have the basic programmers. At some point you need to interface that µC to the outside world, so basic electronic knowledge is needed.
  3. Jaguarjoe

    Active Member

    Apr 7, 2010
    Picaxe microcontrollers are cheap, easy to program and only need 2 resistors and a cable to program. All of the software you need is free from their website and all of the programming is done in the Basic language. A great number of 7th grade kids work with them. There are 3 manuals on line which components, Basic, and interfacing
    For your application, one the commands is called 'Tune' which allows you to create sound sequences, or songs.
    The guys on the Picaxe forum are adept at walking beginners through the process of creating whatever you'd like to build.
    Last edited: Dec 6, 2010
  4. Wendy


    Mar 24, 2008
    Joe, having said all that, the OP still needs to learn the basics of LEDs. It is a matter of learning to walk before you can run.
  5. Jaguarjoe

    Active Member

    Apr 7, 2010
    This will be useful for years to come, it has a wealth of well written info:

    The DC section has Ohm's law, the Diode section has LED's.

    If Google can't do it, then forums should be able to fill in any gaps that might occur.
  6. bertus


    Apr 5, 2008


    We have our own eBook on site here.
    Take a look at the blue tabs on top of each page.
    Those are the entries to the 6 eBooks, including a reference and worksheet book.

  7. Landwand

    Thread Starter New Member

    Dec 6, 2010
    I apologize for my delay in issuing a reply. My ISP was down for a count, and my mind was far from my hobby. Your help is appreciated nonetheless!

    Perhaps I was not entirely clear in my first post. I do have electronics experience, and I do know what LEDs are and how to use them. I do not have deep understanding of the LED light, but I'd like to think that I do know what I am doing.

    I usually favour putting LEDs in parallel - which is why a 5V regulated supply was never much of an issue for me. Would you recommend that I up my source voltage? Should I reconsider my preference for parallel links?

    To give you an idea of the forgotten knowledge that I once possessed, I built (in school), digital dice, light-chasers, digital LCD number matrix, radio transmitter, and some kind of alarm. I retain some of my knowledge, but it is the deep intricacies that really trouble me today. Most of all, this issue.

    If I have a circuit that has a supply voltage of (for example) 9V, and I am still using my 5V USB power supply, how am I to adapt the entire schematic and its components to run on 5V?

    I have been told that μC's tend to be limited in current output - something like 40 mA - which is a concern for a fellow who prefers his stuff in parallel. I was chatting to this fellow who owns a car stereo store and he was wiring his own circuits, he also showed me on his computer screen, a schematic of a rather complex nature that he redesigned into further simplicity by removing the traditional components and using PICAXE set-up instead. Now, this is really tempting for me, I won't have to re-learn the entire "book" when it comes to electronics, and I won't need a boat-load of components that I cannot easily obtain either. You can do many cool things for my hobby using a μC. However, I do know that there is a heavier financial start-up hurdle, and then there is the issue of programming it, too. (I do remember some BASIC and OOT)

    Does anyone have a recommendation for me with all the above in mind? I'm actually quite tempted by PICAXE as I have not yet taken a plunge and purchased a wack-load of components.

    My thanks to those of you who provided links for me to read. I'll go over a few chapters a night until I renew my fading knowledge. And Bill, a special thanks, as I see that you have taken time to extensively write up the reference materials!

    I put emphasis on my current issue (outlined in bolded text) that troubles me - if anyone can point me in a direction that does not involve transforming my source voltage to suit every circuit that I build, I would be grandly appreciative.
  8. Audioguru


    Dec 20, 2007
    LEDs should not be connected in parallel because each one has a different forward voltage. The one with the lowest forward voltage will hog most of the current then burn out. Then the next one with the lowest voltage will burn out and the remaining current will be too high for the rest of the LEDs and they will all burn out.

    El Cheapo flashlight manufacturers connect their LEDs in parallel because they buy thousands, test and sort them into groups so they are exactly the same and can be connected in parallel. Each ordinary unsorted LED needs its own series current-limiting resistor.

    An ordinary CD4017 IC is a sequencer with 10 low current outputs. Its outputs can drive transistors to boost the current. But its output current is too low for a transistor to drive many LEDs.
    A 74HC4017 has much more output current when needed for transistors to drive many LEDs.

    A 1.5V alkaline battery cell drops to only 0.9V during its life. I made many chasers using ten 1.8V red LEDs that use a 74HC4017 driving them directly without transistors and the LEDs are bright and two AA cells last for months.
    I use four AA cells for 6V that drops to 3.6V for the chasers to use 3.5V blue and bright green LEDs.
  9. scientist123457

    New Member

    Nov 11, 2010
    Give me a few days and I will send you a bunch of LED chase circuits, with values...and, how to cascade them...OK ? Bill
  10. Wendy


    Mar 24, 2008
    The link I referred to on post #2 has a lot of schematics. I also write for the AAC book whose links you see above, I have written the experiments section on 555s.