how to make led blinking by using ic4017, 555timer and LDR?

https://www.dropbox.com/s/pigqhd3miw54sdx/12.PNG


i need blinking the 5 led while in dark condition. after i make this connection, i found that the LDR dint function in this cct. the LED also abnormal blinking.
izit my connection got problem? thx you~

The CD4017 will burn out because the LEDs are missing current-limiting resistors.
The datasheet for the CD4017 says the max allowed dissipation for an output transistor is 100mW but with the 12V supply the typical current in 2V red LEDs is shown on a graph on the datasheet from Texas Instruments to be about 23mA then each output transistor dissipates 230mW.

Why not use a Cmos Schmitt-trigger 2-inputs NAND or NOR gate to make a simple oscillator (one resistor and one capacitor) with one gate's input and it can be gated on and off with the LDR on its other input? When the lighting is dark then the Cmos ICs draw almost no battery current. But your circuit with the 555 ICs draws a fairly high battery current all the time.

Here's my interpretation of Audioguru's idea:




Integrated circuit U1 is the CD4093 Quad Schmitt NAND. Transistor Q1 can be any general purpose low power NPN eg 2N3904, 2N4401, BC107, BC337, BC547 etc. If Vdd = 12V then R2 can be 4K7 and R3 2K2. R1 and C1 determine the flashing rate. You will need to experiment with different combinations to get the frequency you like, but as a guide try C1 = 1uF and R1 = 10K. The value of potentiometer VR1, which will typically be a PCB mounted trimmer, will depend on the value of the LDR. The idea is to adjust VR1 so that the output of U1a is low when the LDR is in darkness but high when the LDR is illuminated. The output of U1a will gate the oscillator comprised of U1b, R1 & C1 on (or off). U1c & U1d act as inverting buffers. The transistor is to provide the LED with the current it needs to be brightly lit while at the same time lightly loading U1c & U1d.

freeze1010 said:

https://www.dropbox.com/s/pigqhd3miw54sdx/12.PNG


i need blinking the 5 led while in dark condition. after i make this connection, i found that the LDR dint function in this cct. the LED also abnormal blinking.
izit my connection got problem? thx you~

Click to expand...

Hi

Can you provide more of a description on what this this circuit is supposed to do?

thanks..

eT

The CD4017 is supposed to blink each of the 5 LEDs in sequence.

The left side 555 is a monostable to provide a delay before it activates the right 555 but it is triggered continuously by the LDR so it never times out.
The right side 555 is a mess of wires that do nothing. I think it is supposed to be an oscillator that clocks the CD4017.

The LDR is supposed to activate the circuit when dark but the 555s will drain the battery all day long.
The LDR should connect to the reset pin 4 of the 555.

audioguru said:

The CD4017 is supposed to blink each of the 5 LEDs in sequence.

The left side 555 is a monostable to provide a delay before it activates the right 555 but it is triggered continuously by the LDR so it never times out.
The right side 555 is a mess of wires that do nothing. I think it is supposed to be an oscillator that clocks the CD4017.

The LDR is supposed to activate the circuit when dark but the 555s will drain the battery all day long.
The LDR should connect to the reset pin 4 of the 555.

Click to expand...

lol...thanks AG...

eT