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Posts posted by Nettron

  1. What program do you use to convert GIF to JPG?
    Will it also convert BMP (huge file) to JPG?

    I use Irfanview, it can convert a great many file types. I mainly use its screen capture feature on the options tab, with it i can copy, save to a file and convert a screen image in just one click.

  2. 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.


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

  3. 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

  4. Appearently not all that original .


    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).

  5. 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.

  6. 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:


    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.

  7. 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.

  8. Desmond, i see what you mean but im assumimg you will not be using the tester on an IC that has power connected to it ?
    To better explain what i mean with the sequencing scheme would require a schematic. Not sure what kind of results it will give you i havent breadboarded it yet but looks feasable. I can draw up and post a schematic a day or so if you dont mind the wait.

  9. MP, im aware of what is meant by pins being shorted together, what im getting at is that internally IC pins generally do not short together, a short occurs from input to power supply ground or Vcc, depending on polarity.

    If by "shorted together" the OP is referring to bad soldering between pins then the LED scheme would suffice. Obviously when an LED is connected across two pins ( parallel) that have bin soldered together and power is supplied to the LED it will not light up.

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