Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

How do I reduce the output pulse length of the 4017?

Status
Not open for further replies.

Zebo

New Member
I have a 4017 decade counter giving me a pulse every 10th pulse from a 555. I need the pulse from the 4017 to be adjustable to about 20ms. Is there an easy way to do that or must it go via a 555 once more?
 
The output pulse length of a CD4017 is 1/10th the total time for 10 pulses.
A highpass filter will reduce the time of each pulse.
 
Cbit is your counter output bit. The network consisting of R1 C1 and D1 applied to the input of a hex inverter will create a pulse that you can set the width of.
 

Attachments

  • DF24.png
    DF24.png
    40.8 KB · Views: 234
Or replace the entire mess with a $1 micro processor.

And take the next six months of your life to figure out why the damn thing wont assemble or compile, or produce bits compatible with your loader, or why your config bits are wrong, or ...
 
Last edited:
I'm with MikeMi on this.

Two months ago, I refused to try to repair a refrigerator because it had a microprocessor trying so save energy by controlling a 4 watt fan motor. After the manufacturer's techs tried to fix it 6 times, they gave the customer all his money back and threw the refrigerator in the dumpster. I calculated that the microprocessor would have required 178 years to save enough electricity to pay for a replacement microprocessor board. Some things just don't work as well with microprocessors.
 
Or replace the entire mess with a $1 micro processor.

Why spend as much as that? :D

Do away with the 555, and the 4017, and just do the whole thing with a single 4093! (See sketch)

Have to agree with MikeMl and Bychon on this one.
I have known several occasions when the project that's going to be 'nice and simple' with a microprocessor ends up being done with logic, simply because the software guys can't seem to get the program to run reliably in the time scale!
Of course, there are many projects that simply wouldn't be feasible whithout them. But not all!!
 

Attachments

  • pulse genarator.jpg
    pulse genarator.jpg
    90.6 KB · Views: 245
@bychon
At times micro controllers are used as a sales gimmick. This seems to be one of them.

I have no idea why the repair tech was unable to make it work. Tossing it out seems strange an I hope is is looking for a new job about now.

One problem I see is that the manufacturers overprice the replacement boards because they can. It is not due to the technology.

When my 10+ year old sears microprocessor controlled clothes washer died I got a replacement board with all the relays etc for $70 from a vendor in Mexico. I has run another 5 years without trouble. All the controls work as well as new. No worn out timers or half dead switches.

@Mike
You do have to RTFM once in a while. I teach kids to use them.
 
Last edited:
Mike
You do have to RTFM once in a while. I teach kids to use them.

I have used PICs since the 1980s. However, for someone that has never used one for anything, there is a huge learning curve.
 
Sales gimmick...as in, "Ooh it's Energy Star Efficient!" or, "hugga hugga heat pump" (not in south Florida!).

You can be sure more than one technician made the decision to toss the 'fridge in the dumpster. That was the mfg's tech team. I don't know why they couldn't fix it with all the information available from their own factory, but I'm way glad I didn't get my tit in that wringer!

I have done discreet designs too replace some microprocessor boards and found that some of them actually needed a microprocessor, but I dread the day when I can't buy a flashlight without a digital controller in it.
 
I have a 4017 decade counter giving me a pulse every 10th pulse from a 555. I need the pulse from the 4017 to be adjustable to about 20ms. Is there an easy way to do that or must it go via a 555 once more?

some people have no imagination. while you do not need anything as complicated as a 555, the principle is the same: use feedback from the output that you want to change the duration of back in to the 555.
 
I have a 4017 decade counter giving me a pulse every 10th pulse from a 555. I need the pulse from the 4017 to be adjustable to about 20ms. Is there an easy way to do that or must it go via a 555 once more?

And my question is why do you need this certain pulse width? Most designs are edge triggered and not level sensitive. You might want to reconsider your design and go with a more conventional method, ie. edge triggered synchronous logic. Knowing more about what your trying to do will result in a better answer.
 
Last edited:
Clock pendulum Regulator

Thanks for the response from you all.

I have learnt my first lesson in this Forum, give more info else the thread will never end. I wanted to be as brief as possible, but will now take a new approach.

I repair and restore church clocks. This started as a hobby a few years ago when I retired.

These clocks are not quarts driven and many are still hand wound since they are 50 years and some even more than 100 years old. It is a mission to keep them on time once fixed.

I developed a system to regulate the rate of the clock by "interfering" with the swing of the pendulum.

I have the first system running. It is a logic arrangement with three relays, two transistors to amplify the pulse per second from a GPS receiver, and a few more bits and pieces which I will call the controller. I installed it a few weeks ago and it works beautifully. :)

The controller receives the PPS from the GPS, the transistors amplify the pulse, this pulse goes via two glass reed switches in close proximity to the pendulum to which a permanent magnet is fitted. This pulse then passes through to the controller whenever the pendulum is out by more than a few milliseconds and thus passes over a reed switch which closes the contacts. The controller then sends 12V @ 1Amp to the gadget which will correct the pendulum's swing. It works very well, but my aim is to replace this with a board without mechanical parts. Also, the pendulum of most of these big clocks swing 27 times per minute (ticks 54 times per minute). Very few tick 60 per minute and some only 30 per minute.

So, my present controller only works for very few clocks. I need the GPS pulse per second to be divided by 10 so that the pulse always coincides with the pendulum of ALL clocks in a predictable position when the pulse arrives. One size fits all, in other words.

What I have so far:
Darlington pair to amplify the GPS pulse, 4017 to divide by 10 (here is my problem), the divided pulse goes via reed switches, when it passes through one of the reed switches it will go to one of the two 555 timers, one for slow and one for fast. One of these timers will then send a 9 second amplified current to the gadget that does the regulation. Then the system rests until the clock is out once more. This will happen infrequently as the clock should also be able to keep reasonable time.

It effectively keeps the divided pulse between the two reed switches. So, if the pulse from the 4017 is 1 second, it will fire both reed switches every beat.

It takes the pendulum (about) one second to swing from one side to the other. In half its path I have one reed switch about a quarter from the swing extreme on the left and another a quarter from the right, so the time taken from one reed switch to the next is less than 500ms, When the pulse coincides with one reed switch while closed by the magnet the pulse goes through and the system will adjust the rate, lets say faster. When it coincides with the other reed switch in the closed position, the clock needs to slow down.

I do NOT have an electronics background, but I am learning fast. So, I have some questoins.

Audioguru, what is a highpass filter?

MikeMI, you are way above me. It looks interesting, can you explain more?

3v0, Sorry, I agree with MikeMI, it will take me forever and I want to build something I understand and fix when it breaks.

bychon, I am so with you on this.

rogs, Sorry, I have wasted your time. After reading the above you will see I need to use the 4017 to get a pulse every 10 seconds. The accuracy of the pulse is taken care of by the American Defense Force and that is to the nanosecond, so less work for me. The clock will be accurate year after year. All I need at this stage is to shrink the output from the 4017. Sure I will need more help after that.

MikeMI, 3V0, Yes, let me get past the present hurdle and I will attempt the PICs. I am also a computer programmer and have done some work in C many years ago. Assembler, no thanks.

Ubergeek63 You may have something here, but I cannot see it through. So the 10th pulse from the 4017 will go forward and do its work, but also stop/reset the 4017? Pls give more info.

Mikebits Yes, you are right. Above I hope I gave a full description of what I want to do.

Please note that in South Africa we sleep while most of you are posting, so have patience with me.
 
Audioguru, what is a highpass filter?
A highpass filter is a coupling capacitor feeding a resistor to ground. It reduces low frequencies and passes high frequencies.
When a pulse is its input then its output is a pulse with reduced duration, calculated roughly R x C.
 
A highpass filter is a coupling capacitor feeding a resistor to ground. It reduces low frequencies and passes high frequencies.
When a pulse is its input then its output is a pulse with reduced duration, calculated roughly R x C.

So are you saying that the 1 second pulse from the 4017 can be trimmed to R X C, say 100ms? Can you give me a circuit for that and I will try it?
 
And take the next six months of your life to figure out why the damn thing wont assemble or compile, or produce bits compatible with your loader, or why your config bits are wrong, or ...

worry about six months lost of your life. :D

Boncuk
 
worry about six months lost of your life. :D

Boncuk

Hell yes, I could be flying, boating, hiking, instead of wasting time in front of this time toilet (computer) ;)
 
...
MikeMI, you are way above me. It looks interesting, can you explain more?
...

Think of the stuff in the dashed box in the simulation as your GPS disiplined counter...

It has a fixed period (derived off the GPS). You want to extract either the positive or negative going edge from some counter bit V(Cbit) and use it to create a fixed, but relatively narrow pulse width. I show how to select the falling edge to create a fixed width pulse V(Pulse). Look at the traces in the simulation. Note how the width of V(Pulse) is determined by R1 and C1. Vdd can be anything appropriate for the 4017 and 4049 CMOS logic.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top