Hi All,

I need to clock the 4017 counter from two paths .
#one from push button (the distance between the button and the counter 20 M)
#and the other one from mcu ..

does the circuit below satisfy what i need or need to add more elements ?





Regards

 

If you can't guarantee that the MCU and switch will ever be in conflict, you should use a gate instead of wire OR'ing.

The switch will require debouncing.

 

Definitely not.
Firstly, you need to debounce your push button.
Secondly, you need special drivers in order to send the signal over 20m. You might want to consider current loop or RS-232/RS-422/RS-485 driver/receiver.

Then you need a way or OR'ing the two signals such as open collector, open drain, tristate, diodes, wired-OR, digital OR gate.

 

Thanks All

only the switch is far away about 20 M from the counter but the resistor and the debounce circuit will be closed to the counter .
So still need a driver ?

 

The 4017 clock input advanced the count on the positive-going edge. If you want to use a grounded switch as shown, tie the clock input to Vdd and drive the Enable input with a negative-going edge. The 4017 internal schematic shows that this will work.

What is the power supply voltage?

ak

 

Thanks All

only the switch is far away about 20 M from the counter but the resistor and the debounce circuit will be closed to the counter .
So still need a driver ?

Yes.

 

The 4017 clock input advanced the count on the positive-going edge. If you want to use a grounded switch as shown, tie the clock input to Vdd and drive the Enable input with a negative-going edge. The 4017 internal schematic shows that this will work.

What is the power supply voltage?

5 V
ak

Yes.

could u suggest a driver to use ?

 

could u suggest a driver to use ?

Assuming that you want to put a passive switch 20m away, I would use a 220Ω resistor as my driver.

 

Assuming that you want to put a passive switch 20m away, I would use a 220Ω resistor as my driver.

Do u mean as seen in circuit below ?

 

Here's the simplest circuit I could come up with.
It uses the inhibit input for the MCU clock and a large RC filter on the PB line to debounce the switch and suppress noise pickup.
The simple RC debounce will work since the CD4017's clock input is insensitive to clock rise and fall time as shown below.
The one possible disadvantage of this simple circuit is that it triggers on the release of the push-button, not when it's pressed.

 

Do u mean as seen in circuit below ?

R5 can be deleted because R6 and R7 limit any external currents.

Your debounce period is less than 1 ms. Increase C4 to 10 uF for more effective debouncing.

When both inputs are off pin 14 will float, a CMOS no-no. Add a 10K pull down resistor from pin 14 to GND.

ak

 

Here's the simplest circuit I could come up with.
It uses the inhibit input for the MCU clock and a large RC filter on the PB line to debounce the switch and suppress noise pickup.
The simple RC debounce will work since the CD4017's clock input is insensitive to clock rise and fall time as shown below.
The one possible disadvantage of this simple circuit is that it triggers on the release of the push-button, not when it's pressed.

View attachment 129300

View attachment 129301

R5 can be deleted because R6 and R7 limit any external currents.

Your debounce period is less than 1 ms. Increase C4 to 10 uF for more effective debouncing.

When both inputs are off pin 14 will float, a CMOS no-no. Add a 10K pull down resistor from pin 14 to GND.

ak

Thank you for your appreciated effort ^^
I will try the circuit soon then post the result

 

Looking better.

Eliminate R5.
R6 is the 220Ω resistor used to drive the 20mA current loop.

 

Looking better.

Eliminate R5.
R6 is the 220Ω resistor used to drive the 20mA current loop.

u mean like this ?!!

 

Yes.
You may have to increase C4 to about 10 to 22μF.

 

The debounce time constant is worse than before. Now it is only 22 us. It should be at least 10 ms, usually more like 20-50 ms.

ak

 

Yes.
You may have to increase C4 to about 10 to 22μF.

And add a small resistor (e.g. 100Ω) in series with the switch so the large current spike from discharging the capacitor doesn't weld the contacts.

 

thanks all

so the circuit become like this ?



R5,R6,R7 and C4 should be close to switch(20 m from the counter) or should be close to 4017 ?

Regards

 

Components go close to 4017.
Note that the connection to the pushbutton is via 20m length of paired wires (i.e. 2-conductor cable).

Hook it up and try it out.

What you are looking for are:
1. Does pressing the pushbutton cause a transition of 4017?
2. Do you get a single increment or multiple increments (i.e. switch bounce)?

 

I need to control water pump on/off using two methods:
1-Wired:using a push button placed in our park.
2-Wirless:using rf remote control i will use the following one instead of using rf link with mcu

http://mikroelectron.com/Product/4-Key-4-CH-Wireless-Remote-RF-Module-4CH/

So any pulse comes from push button or the rf remote will toggle the state of the motor ^^

Regards