Hello ACC forum,

Planning to build an LED display called LED Dice with Slow Down.
http://www.555-timer-circuits.com/led-dice.html
1. I get the pin 3 from the 555 timer going to the clock, pin 14,
on 4017 decade counter. But what makes the clock slow down?

2. In the upper left hand section of the schematic, in the components
going into the 555 there are three components that look like
resistors. Not sure I have got them right
10 M = 10 mega ohms
3M3 = 3,3 mega ohms
4M7 = 4.7 mega ohms
Is that right. I could find resistors with these values
at DigiKey but I have never used resistors with such
high resistance.
Just want to make sure I have it right before I start building the circuit.

Thanks.

Allen in Dallas

 

The high R values are needed for the touch switch. If a pusch button SW were used, R values could come down.

 

Hello Bernard and Forum,

Sorry about the thread title misspelling.

Actually had planned on closing the circuit with either a relay or a transistor
operated by a PIR sensor.
The PRI sensor, (HC-SR501) outputs a s.s volt signal for about 5 seconds.

Would the value come down half or three quarters?

Thanks

Allen in Dallas

 

1. The frequency of the 555 depends on the 100nF , 10k, & conduction state of BC557. With 1uF discharged, 555 stopped or verry slow. Shorting touch pins, charges 1 uF, turning on BC; 555 @ about 10 k Hz. As 1 uF discharges, 555 slows down over about 10 sec.
2. Decay rate depends on 1 uF & 10M. If C is increased to 10 uF then 10M is 1M.

 

This is a better link to your circuit. Note the modification at the bottom of the link, your link above does not seem to reflect the modification. The circuit is based on a very old circuit. The idea was the 555 would free run in an astable mode so all the LEDs were On/Off so fast they appeared as a blur and when a button was released the oscillator simply stopped wherever it was incrementing the 4017. This newer approach is pretty cool. When the wires are bridged with a finger the action of the top left transistor and the capacitor up there cause the oscillator (555) frequency to sweep down to a slow stop. Nice touch.

<EDIT> I see as I was slowly typing away at my snail pace Bernard answered the question. </EDIT>

Ron