Hi,everyone. Im newbie in doing ee project. I need using ldr sensor to blinking 5 led. But i cnt make it after had many tried. I had attached my cct picture. Can anyone tell me how to fix it... thx you so much...

 

Welcome to the forum!
1) The unused Q outputs of the 4017 should be left open-circuit; not shorted to ground as shown.
2) Exchange the positions of LRD1 and RV1 if you want the 555 to trigger when the light comes on.
3) You may need to add a low value (say 1k) resistor in series with the Q output of U1 to prolong the clock pulses going to the 4017.

 

The R value of second 555 is zero, what do you expect the circuit to do?

 

Wanna the 5led blinking when in dark condition. Thank you.

 

The R value of second 555 is zero, what do you expect the circuit to do?

Wanna the 5led blinking while indark condition

 

Welcome to the forum!
1) The unused Q outputs of the 4017 should be left open-circuit; not shorted to ground as shown.
2) Exchange the positions of LRD1 and RV1 if you want the 555 to trigger when the light comes on.
3) You may need to add a low value (say 1k) resistor in series with the Q output of U1 to prolong the clock pulses going to the 4017.

Thank you for your reply. As your mention in(2) , izit the variable resistor still function in adjust the sensitive of ldr?

 

Wanna the 5led blinking while indark condition

You didn't get my point.
I mean that the 555 oscillator should be have a resistor and cap to generate the pulse, but the R value of second 555 is zero, so you need to adding a resistor between two 555.

 

You didn't get my point.
I mean that the 555 oscillator should be have a resistor and cap to generate the pulse, but the R value of second 555 is zero, so you need to adding a resistor between two 555.

em, then i need connect which pin of the 555 timer?

 

In series with a resistor from the pin 3 of the first 555 to the pin 7 of the second 555.

Your second 555 had some problem, so it won't work.

The first thing is to disconnect the Pin 7 from Pin2,6, the Pin 2,6 should be connected together, and in series with a resistor to the Pin 7, and the Pin 7 in series with a resistor to the Pin 3 of the first 555(it was described on the first paragraph).

 

Don't forget Alec_T's first point.

If the unused outputs are connected to ground, you can let the magic smoke out of the chip and destroy it in the process.

The 4017 should be wired similar to this:

 

i had follow your instruction. but cnt make it. just second LED light up only.

 

i had try this connection. but still cnt made it.

 

I can't see the circuit.
If you already disconnect the wires as djsfantasi mentioned, and connected the R as I described on #9, but the second 555 still didn't work, then you should disconnect the resistor from pin 3 of the first 555, and connecting the resistor to Vcc, and to see how's going.

 

If the resistor was too small, the leds will be flashing more fast, if all the leds was flashing almost the same time, then the resistor could be too small, so the frequency is too high, you may using the resistors as the first one is 1K from the pin 3 of first 555, and the second resistor is 100K that it will be connecting from pin 7 to pin2,6 on the second 555, and the cap using 1uf, when the 555 is working ok, then you can adjust the value of cap or the second resistor, the first resistor just keeps it on 1K.

 

 

I still can't see the circuit.
The below is a cmos 555, if you are using TTL type as NE555 or LM555, you can using the R1=1K,R2=100k,C1=1uf, that's all described on 14#.

 

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


i still cant make it. can u help me to take a look for this cct? plz. thank you.

 

I redraw the circuit, and changed some connection and added the wires, you can see the blue color, and you should recheck all the circuit.

1. If you want to test the LED function, you can disconnect the P point on pin 3 of U1, and connecting R2 to Vcc, if the 555 function is ok, the LED on CD4017 should be flashing.

2. I also drawn another way to using CD4017.

3. If you want to test LDR function, then you can using the multimeter to measure the pin 3 of U1, and cover the LDR to see how the voltage changing.

 

LEDs, 555s, Flashers, and Light Chasers

I cover 555's and 4017/4022's in this article.

 

i had measure the voltage of pin3 in U1, the voltage keep changing whenever bright condition or dark condition, voltage reading very unstable. izit meant that LDR dint function in this cct?