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555+4017 help please

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tidos76

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ok i have them set up and working. the 4017 is running 5 leds in a back ad forth pattern (nigh rider pattern) my goal is to have this run 5 relays, because the lghts i will be running have to have 12v. the relay will work with 6v+. my problem is when i turn the voltage up over 9v the 4017 goes nuts, i just get a random flash pattern and some of them dont even come on. but anything -9v it works perfect, but wont produce the 6v needed to hit the relays (due to the 3v drop. anyone had this problem? or know what i can do to fix it? i need this to run on 12-14v i know thw 555 and 4017 are rated to 15v. Thanks in advance.

schematic is like this except i;m only using 5 leds. outputs are tied using diodes but instead of the coupling they hav i;m using (1,5)(10,6)(7,9)(4,11)(2,3) hope that makes sense
 
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MikeMl

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Most Helpful Member
Do you have snubber diode(s) around the relay coil(s)? Have you looked up (data sheet) how much current an output fromt he 4017 can source vs how much current it takes to operate the coil on your relay?
 

audioguru

Well-Known Member
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Your 9V needs two bypass capacitors as shown on the datasheet for an LM555.
 

MrDEB

Well-Known Member
need voltage and current of relays

add the by pass caps to the 555 but still need specs on relays.
thinking a simple transistor switch or using mosfets instead of relays is another option.
 

tidos76

New Member
the 4017 was frieken out even without the relay. i added a cap between 15-16 on the cap and it fixed the problem.
 

MrDEB

Well-Known Member
still no info on relays??

the circuit may work now but for how long without proper design.
a 555 will drive an 8 ohm speaker but not for long without being designed properly.
been there done that.
 

audioguru

Well-Known Member
Most Helpful Member
The capacitor you added was a supply bypass capacitor like I said your circuit needs.
The datasheet for the LM555 talks about how it smooths the supply voltage from the high current spikes caused by the 555 from messing up other ICs that are powered from the same supply.

The datasheet for Intersil's Cmos 555, the ICM7555, shows that the supply current spikes from an ordinary 555 is 400mA which will drop the voltage very low without a supply bypass capacitor. The CD4017 counter is messed up when its supply voltage suddenly drops very low.
 
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