60 outputs

Discussion in 'General Electronics Chat' started by FroceMaster, Oct 16, 2014.

  1. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    402
    4
    Hi,
    I have planed to make a clock with second around in circle.
    each LED from 0 to 59 should lid up.
    Could use some 4017 and let each output drive a LED.
    But somehow i can't figure out how to prevent the counter from restarting, and what about the reset at 59-60
    Could it be done with 2 * 4 bit counters ? and some flip-flop's or ??

    in the scematics i have done it with up to 59, but how do i get it to reset at NeXT input ?
    The reset from all 6 counters will be together and should be reset after 59, but i cant figure out how to connect it.
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    I don't think the 4017 is the way to go. I would build a binary counter out of flip-flops. You need 6-bits. If you use 4013s then you will need 3 of these. You could also use 1 1/2 4-bit counter chips. Using 4013s has advantages in that Q and /Q are available for each bit. This will be useful.

    Now the decoding to drive the 1 of 60 LEDS. A nice way of doing this is to use two 3-bit binary to 8 line converters. Just two, and multiplex your LEDs. Eight pull-up drivers and eight pull-down sinkers. Use two 4051s. The first 4051 is driven by the 3 lowest bits of your counter. The second is driven by the 3 highest bits of your counter. Use an 8-input gate to reset your counter. This is where the complimentary outputs are useful.

    Enough clues?
     
  3. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    402
    4
    Could be. Could also use a microchip and connect the LED in matrix. 16 outputs should be ok. 6+10 or 8+8
     
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,546
    1,252
    Or, do it all with only two 4017's and no firmware. Electrically connect your 60 LEDs in a 10x6 matrix. Clock the 1st 4017 with the Seconds clock. Drive the 10 "rows" with the first 4017. Clock the 2nd 4017 with the carry output from the first one. The 2nd 4017 outputs 0-5 drive the "columns" with sink drivers like 2N4401 transistors and current limit resistors. Output 6 resets the 2nd 4017; no need to reset the first one.

    ak
     
  5. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    402
    4
    Possible but then some flip flop. Or how will the lights stay on ?
     
  6. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    How do you want the LED's to operate? Do you want one and only one LED on at a time? If so, AnalogKid's suggestion should work nicely. Each LED will come on and stay lit for about one second.

    If you want all the LED's to come on (one at a time around the clock face), take a look at this. The LED's will come on one at a time and stay lit until all 60 are on, then they'll turn off one at a time until all are off, then repeat.

    If you need transistors, consider using ULN2803 (5VDC) or ULN2804(6-15VDC). These have eight outputs on a single IC and don't require a base resistor.

    You can do this with a uC of course as you described. Most can handle 20mA or so, so you wouldn't need transistors unless you're using high current LED's. You can either use a single uC with plenty of I/O's or use a smaller one with an I/O expander like the MCP23017 (I2C) or MCP23S17 (SPI).
     
  7. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    Two CD4017 and ULN2803*2, you can do it to the max Qty as 10*10.
    One CD4017 for row and another one for column.
     
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