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flash LED newbie question

Discussion in 'Electronic Basics' started by [email protected], Apr 11, 2007.

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  1. Guest

    I want to build a timer which, when activated, causes an LED to flash
    (approx 0.5 to 1 hz, but the precise frequency is not that important)
    for 30, 60, 90 or 120 minutes (adjustable). Ideally, power supply
    would be 1.5 to 3V. Since I am new, simplicity would be appreciated.
    Thanks for any help.
  2. Jan Nielsen

    Jan Nielsen Guest

    If you are up for a challenge, it can be solved with a PICAXE.

    Its a microprocessor that can be programmed in a much easyier way than
    the C/assembly processors.

    A 08M picaxe is about 3$
    A download cable to program it, the same.
    The program will be a few simple lines, and you can reprogram the chip
    using just the programming cable (and 2 resistors).

    It wont be 100% precise, but probaly enough for your use.

    If you want to solve it without using a microprocessor, I think the
    timing will be the problem.
    The blink rate can be done with a 555timer, but the delay for
    30-120minutes may be a problem to get precise.

    If you want to try with the axe, I can make the program for you.

  3. default

    default Guest

    What would be the bare minimum of parts to get started using a picaxe?

    USB cable, software, some kind of prototyping (switch led) board?
    What would you recommend for a pic-08?
  4. Jan Nielsen

    Jan Nielsen Guest

    default skrev:
    They have some pretty cheap (From 10GBP) starter sets with cable, board
    and a pic.

    But if you want to buy the parts alone
    PICAXE 08(-M)
    Download cable (Can make it yourself, but its 3GBP, so...)
    2 resistors (10K and 22K, 1/4W should be fine)

    a solderlessboard or something to test on
    and some boardpins to make the connecter from the download cable.

    if you only have usb, you will need a usb-2-serial converter.

    their hp is

    The 08 is cheap, but its pretty limited with memory, so only useful for
    small projects, it will hold about 40lines of basic.

    I use 08-M for small projects, and 18X for more advanced projects.
    The "hello world" program is to flash a led, but that gets borring fast.
    For testing a solderless breadboard will do fine, so you can replace

  5. ehsjr

    ehsjr Guest

    For simplicity, use a lamp timer like Intermatic TN111C Lamp
    & Appliance Timer ($6.49 at Amazon.Com). Plug a 5V DC regulated
    wall wart supply (CAT# DCTX-512 $3.50 at
    into it, and connect the supply to a blinking LED (CAT# LED-4
    $0.90 for 2 at allelectronics) through a 100 ohm resistor.

    ------ --------
    | |---| +|---[100R]---[LED]---+
    |TN111C| |DCTX-512| |
    | |---| -|--------------------+
    ------ --------

    To operate, plug the timer in and set the ontime and off
    time buttons 30, 60 90 or 120 minutes apart. Then turn the
    timer dial until the LED starts to blink. It will blink
    for the duration you choose, then stop. It will repeat the
    next day and every day thereafter, unless you unplug it.

    If you want a little more complexity, the TN111C can
    be replaced by a kit: QK152 $12.95 at
    It requires a 12 volt power supply (CAT# PS-1251 $8.50 at
    allelectronics) and your circuit would change:

    | |
    ------- | ---------- |
    | +|-+-| NC|--+
    | 12V | | Qk152 |
    | Wall | | COM|---[1K]---+
    | Wart | | | |
    | -|-+-| NO| [LED]
    ------- | ---------- |
    | |

    This will increase your cost, but you'll get a little more
    electronics experience assembling the kit and adjusting the
    timing, and it won't need to be unplugged to prevent it from
    turning on again the next day. Later on, once you have
    that working as you like, the 12V supply could be replaced
    with a DC-DC converter to allow operation from 3 volts
    or 1.5 volts. You would likely want to modify the Q152 as well
    to eliminate the relay which reduces current drain.

  6. jasen

    jasen Guest

    Here's one way:

    I'd not build it till some of the experts here have checked it over,
    I think it'll work, but I could be making some silly mistake.

    | This is an ascii schematic, if the diagram appears garbled |
    | try switching to a fixed-pitch font (courier works well) |
    | pasting it into notepad works well on ms-windows. |
    | or in google groups "view source" (found under options) |

    .----------[R4]-----------------+--- +3V
    | |
    | .--------------. |
    30min | / | | | | |
    +---/ -->|---[ 1 \_/ 16 ]---+--.
    | | | |
    60min | / | | |
    +---/ -->|---[ 2 15 ] |
    | | | |
    120min | / | | o |
    +---/ -->|---[ 3 14 ] |-| restart
    | | | o |
    | | | |
    | [ 4 13 ] |
    | | CD4060BC | |
    | | | |
    | [ 5 12 ]------+---[R5]---+- 0V
    | | | .---------. |
    | | | | | || |
    | [ 6 11 ]-+-[R2]--. +--||-'
    | | | | | ||
    | | | | | c2
    | [ 7 10 ]---[r1]--| |
    | | | | |
    | | | ||   | |
    | 0V ---[ 8 9 ]--+-||---' |
    | | | | || |
    | `--------------' | c1 |
    | | | LED
    | `--------|---|<----[r3]--+3V
    | | Hi Eff
    c2 1nF
    C1 1uF
    R1 2M
    R2 1M
    R3 820
    R4 100K
    R5 100K
    Led some high-efficiency type.
    Other diodes 1N914 or 1N4148

    for 90 minutes turn both 30 and 60 minute switches on.
    ( 150, 180, and 210 minutes can also be got using
    combinations of switches. )

  7. default

    default Guest

    Thanks for the ideas.

    This looks a lot more promising than the $20 stamps I've used.

    I found a seller in the US that has them (08M) pretty reasonable ~$10
    for three, ordered that, and a small board for prototyping that
    carries the serial jack, regulator, and socket for pic for $8, USB to
    serial cable $14, and the "Programming and Customizing the PICAXE
    Microcontroller" book for $21. Has the stuff - the book
    I ordered via ABE books on line.

    The 18X is only a little more money.

    One question - is there any danger of inadvertently overwriting the
    boot strap loader or is that protected?
  8. Jan Nielsen

    Jan Nielsen Guest

    default skrev:
    As long as you use their program there shouldnt be a danger.
    Since the chips is regular PICs with a bootloader they can be programmed
    in a regular programmer, but then you risk overwriting the bootloader.

    phanderson has a lot of other neat projects too :)

  9. Jan Nielsen

    Jan Nielsen Guest

    default skrev:
    By the way, check my post in the "Thanks" thread, theres a pretty nice
    simulator to catch to stupid mistakes before programming the pic.

    although it cant debug much about inputs it can check the code and stuff.

  10. default

    default Guest

    Thanks again. Can't wait for the stuff to get here. Just got a
    confirmation that the book shipped.

    I noticed in one blog that the author recommended running at 3 volts
    because it makes blowing an output line less likely. 3 V will make it
    handy for battery projects.
  11. jasen

    jasen Guest

    should be R1 1M
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