LED dice w slow down & PIR start

Discussion in 'The Projects Forum' started by allenpitts, Mar 12, 2015.

  1. allenpitts

    Thread Starter Active Member

    Feb 26, 2011
    Hello Forum,

    I posted a question similar to this but have done some schematic work so I started a new thread.

    I found this circuit on the ole interweb:

    It simulates rolling a die with a gradual slow down to end value.
    Would like to start it with a PIR sensor. So I made these mods:
    The part I am worried about is R1, R2, and R4. Bernard pointed out that R2 could be lowered to 1 mega ohm if c1 was raised to 10 uf. But with the touch wires eliminated do the values for R1, and R4 still have to be so high? If not, as Bernard implied, what would be the right range? Maybe something like
    R1 = 1 mega ohm and R2 = 2 mega ohms?


    Allen in Dallas
    PS Thanks to ReloadRon for the tip on the R17 modification.
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    the relay coil needs to go between the positive supply and the collector of the transistor, the contacts of the relay just need to short out the touch contacts.
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    You can try changing C2 to 1 uF & R4 & R1 to 1M.
  4. MCU88


    Mar 12, 2015
    For the purpose of? Show some maths and reasoning or something. Don't just pull figures out the air without explanation.
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
    A little higher value of R4 will keep the slow flash rate from beeing chopped off early. If R4 is eliminated, flash rate is around 2 to 3 sec & may not stop if there is any T1 leakage; suggest 2 to 3 M.
    To shorten the time to where flashing is perseived, a 470k R can be added from either side of touch wire, & ground or C1. This will keep C1 from fully charging.