ST. Patrick's Day Hat

Discussion in 'The Projects Forum' started by k7elp60, Mar 23, 2015.

  1. k7elp60

    Thread Starter Distinguished Member

    Nov 4, 2008
    DSC00072.JPG DSC00086.JPG ST.PATTY HAT.jpg Here are some pictures of the lighted hat I wore on my head on the 17th of this month.
    I purchased some green T1 size LED's on EBAY some months ago that were designed for 12V operation, so they had a series resistor and leads attached. I thought they were still to bright for a 9V battery so a added the 680 ohm resistor from pin e of the 4051 to the +9v source.

    Circuit operation of my circuit called holiday display. U1 is a quad 2 input nand Schmitt trigger. 3 of the gates are used as astable oscillators. The frequency of the oscillators is very close to the following formula: Frequency=1/2.2RC. U2 is a 1 of 8 switch. The three oscillators feed the AB&C inputs and the 1 of 8 outputs depends on the binary code to the inputs. The IN/OUT pin 3 is tied to Vdd through a resister R4 so the outputs are + with respect to Vss or ground.

    I chose the 4051 and the 4093 a number of years ago because with the adjustable frequencies of the 4093 the Led’s can appear to be random with no definated sequence. Also with the outputs high thru a resistor connected between pin 3 and Vdd multiple LED’s can be put in series and still only require on current limiting resistor. I used the CMOS Cookbook by Don Lancaster as a guide. He specifies a maximum current of 25mA for the IC. There is also about 125 ohms resistance between pin 3 and the outputs, so sometimes this 120 ohms has to be figured in the maximum current for the LED’s.

    I have over time used 10mA as maximum current for the older LED’s, but a lot of the newer one’s that are much brighter the current can be much less.
    Moderator if this meets the requirements for a completed project, please move it to that area.
    Last edited: Mar 23, 2015