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4017 Decade Counter

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shaneshane1 said:
Confused a little :confused: , so does this mean that the capacitors negative pin is +V until the cap is charged?
The charge on the capacitor can't change instantaneously, which means the voltage across it can't change instantaneously. In your series RC circuit, if you put a very fast step of voltage on the power supply pin, the voltage on the other terminal on the cap will therefore change suddenly also. If the cap was initially uncharged (zero volts across it), the pin connected to the resistor will suddenly jump to the same voltage as the power supply. However, if the supply voltage now stays high, the cap will charge through the resistor until it is fully charged, at which time the voltage across the resistor is zero. So, you created a reset pulse to Vcc, and then the voltage returned to zero, releasing the reset condition.
In the real world, if the power supply risetime is not extremely fast, the cap will be charging while the power supply voltage is rising, resulting in a waveform like the ones I posted above.
 
please help

i want design one circuit to control 5 led only using 1 ic 4017 and 555, but i don't know how to use pin 15 (CLR) of ic 4017. Please send diagram of it to email: vuhung0708@gmail.com

thank a lot
 
please help

i want design one circuit to control 5 led only using 1 ic 4017 and 555, but i don't know how to use pin 15 (CLR) of ic 4017. Please send diagram of it to email: vuhung0708@gmail.com

thank a lot
We don't generally answer requests to email addresses, and you risk getting a lot of spam by publicly posting yours.
The All About Circuits textbook has a discussion about your question . If you scroll down past the ten LED sequencer, they show how to short-cycle a CD4017 to get a repeating 3-pulse sequence. I think you can figure out how to change this to 5.
 
Another related question

I've followed conversation above.

In an RC circuit as shown to auto reset 4017, we know that when the power 'On, the cap is fully charged.
The questions are:
How long does it take to discharge the cap when the power is 'Off'?
Does the 4017 discharge all the cap connected to its pin as soon as it is 'Off'? How?
Thanks for the kindly reply.

Regards,

Luky
 
I've followed conversation above.

In an RC circuit as shown to auto reset 4017, we know that when the power 'On, the cap is fully charged.
The questions are:
How long does it take to discharge the cap when the power is 'Off'?
Does the 4017 discharge all the cap connected to its pin as soon as it is 'Off'? How?
Thanks for the kindly reply.

Regards,

Luky

hi,:)
The thread is a year old and the reset circuit seems to have gone.? but I'll try to answer.

Was this description the circuit you are asking about.?

The original circuit showed a capacitor and resistor in series.
The cap was connected to +v and the Resistor to 0V.
The junction of the cap and resistor was connected to the base of a transistor.
 
Last edited:
How long does it take to discharge the cap when the power is 'Off'?

It takes a little bit longer for the capacitor to discharge then it is charging up, due to other energy storing devices between Vcc and 0V.

Does the 4017 discharge all the cap connected to its pin as soon as it is 'Off'? How?

No. It does not.

However, when you remove the power, the load between Vcc and 0V will continue to operate and "consume" energy, until the voltage Vcc drops to a low level.

When Vcc voltage drops, the voltage on the capacitor will then be higher than the Vcc and thus current will flow from capacitor to Vcc. The charges on the capacitor will now "release" back to the Vcc bus and help to lengthen the drop of the Vcc voltage. This is how the capacitors get discharged.
 
please help

i want design one circuit to control 5 led only using 1 ic 4017 and 555, but i don't know how to use pin 15 (CLR) of ic 4017. Please send diagram of it to email: vuhung0708@gmail.com

thank a lot

Connect it to ground and the counter will do it's job. Connected to VDD it will quit.
 
Hi,
Thanks for your reply. I salute you all.
What I could conclude in 'Off' condition is:
As pin 15 of 4017 is directly connected to the base of an NPN transistor (inside of the IC), the cap then easily discharges through base-emitor and any other components forming a closed circuit?
Well, I've just inspired to the cap of a DC adaptor. The cap is still fully loaded despite the AC feeder is off.
Back to the last topic of 4017 reset, does the RC circuit of 100n and 100K ensure autoreset at anytime power on?
Thank you.
 
Hi,
Thanks for your reply. I salute you all.
What I could conclude in 'Off' condition is:
As pin 15 of 4017 is directly connected to the base of an NPN transistor (inside of the IC), the cap then easily discharges through base-emitor and any other components forming a closed circuit?
Well, I've just inspired to the cap of a DC adaptor. The cap is still fully loaded despite the AC feeder is off.
Back to the last topic of 4017 reset, does the RC circuit of 100n and 100K ensure autoreset at anytime power on?
Thank you.
There are no NPNs (or any type of BJT) in a 4017. The 4017 is CMOS. It will discharge through the resistor and the 4017's input protection network when power is switched off. You may need to post a schematic of exactly how you are using the 4017.
 
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