# How to use a 555 clock across a whole circuit?

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
So I am trying some new ideas in a few areas.
But a stumbling block that always hits me is voltage loss or amperage loss or gain loss... im not sure which.

But lets say you have a 555 timer and you want to use it as the clock.
And you want to run 1 decade off of it, that uses 4 numbers and counts to 9999 using 4 subsequent decade counters...

Logic says.

555 timer clock powers decade timer
Decade timer 1 outputs clock signal to second decade timer.

But this never seems to work due to voltage drop.

What I want to know is, and I know its an amateur question... But I have no idea.
And I have been searching for months for a solution... off and on.

How do I prevent that drop in voltage or make that decade counters output signal enough to be seen by the next counter as a clock signal.

What am I missing (without having to go to school to be an engineer(working on that too))

#### ericgibbs

Joined Jan 29, 2010
14,220
hi Andrew.
Do you have a circuit you could post, so that we can help with the problem.?

E

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
No sorry.

I can say when I last attempted it, I used a 555 timer as the clock source at 5v and a 4017 as the decade counter.

And I plugged the output of those 4017 into the clock source of the next ones.

Maybe I can ask this a different way.

Anyone know of a way to use 4017's and 555's to count from 1-99 on an segment clock or even just a chain of leds?

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
im not lazy... I just ran out of ideas and the web has thousands of ideas, many of which never work which make it hard to bother trying others ideas. I dont know enough to filter out the good from the crappy schematics.

#### ericgibbs

Joined Jan 29, 2010
14,220
hi,
As you may know a logic IC has a 'fan out' limit , thats the maximum number of other IC inputs that it can drive OK.
4017's are CMOS devices and have a high 'fan out' so that should not be a problem.
The 555 you have may be a TTL version,?? these have different logic thresholds than CMOS, so that could be your problem.

Can you post a photo of your project, 'throw us a bone'

E

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
what is the difference between a ttl and a cmos 555?

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
this is entirely new to me, I had no idea that there were different versions of 555 timers. Its probably the one chip i know better than anything.
Shows how much i actually know.

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
thanks.
I also just bought the art of electronics.
I think its time to learn it all so I dont need to ask dumb questions

#### ericgibbs

Joined Jan 29, 2010
14,220
hi,
Your questions are not dumb, we have all been there.
I use the free download ExpressSCH drawing program, its got lots of ready made outlines of components and its easy to use.
When you have a logic problem, post a simple drawing and I am sure we can help you.
E

BTW:
Did you see the difference in logic levels for CMOS and TTL in those PDFs and link.?

#### crutschow

Joined Mar 14, 2008
28,216
This is a nit, but a bipolar 555 is not TTL (at least as far as its internal circuit is configured).

#### ericgibbs

Joined Jan 29, 2010
14,220
I would say most engineers do refer to the older 555 as the TTLversion.
Most of us know it only refers to the output specification and not the internal bipolar's.
Ref this clip from the 555 d/s

#### crutschow

Joined Mar 14, 2008
28,216
Most of us know it only refers to the output specification and not the internal bipolar's.
Perhaps.
Call me picky, but I dislike using misleading or sloppy terminology when discussing electronics with newbies.

#### ericgibbs

Joined Jan 29, 2010
14,220
Carl,
I would say we all, including you, could be accused of being sloppy and misleading in many of our posts.
I hope you don't mind, if in future, I take the trouble to point out any sloppiness in your replies.
Normally I make a point of not criticising or nit-picking other members posts, I try to direct my replies to the TS.

My main goal in answering a newbies question is to use the level of explanation, which I believe he will understand.
If he has a problem understanding or complains that 'he already knows that', I adjust my replies accordingly.

Eric

#### crutschow

Joined Mar 14, 2008
28,216
I hope you don't mind, if in future, I take the trouble to point out any sloppiness in your replies.
If it clarifies what I said to the TS, you are more than welcome to do that.
Normally I make a point of not criticising or nit-picking other members posts, I try to direct my replies to the TS.
Then I suppose you are a better person than myself.
My purpose was to clarify the description of the 555 for the TS.
I didn't mean to step on your toes.

Last edited:

#### dl324

Joined Mar 30, 2015
13,554
Anyone know of a way to use 4017's and 555's to count from 1-99 on an segment clock or even just a chain of leds?
CD4017 can be chained to drive as many LEDs as you want:

But you can't do anything meaningful with seven segment displays.

#### BobTPH

Joined Jun 5, 2013
4,053
555 timer clock powers decade timer
Decade timer
Is this statement correct? You are using the 555 output to power ( as opposed to clock) the decade counter? That would explain why you are losing voltage.

Bob

#### AnalogKid

Joined Aug 1, 2013
9,498
555 timer clock powers decade timer
No, it doesn't - or at least, it shouldn't.

This is the problem with trying to discuss a circuit without a schematic. While it is possible to connect the 555 output pin to the decade counter power pin, this is not the right way to go. So, is that really how you have things connected, or is it an inaccurate description of your circuit?

Another thing - in the world of digital circuits, the word "clock" has a one meaning when referring to a signal, and other meanings when referring to a circuit or a device. From your description it sounds like you are designing a time-of-day clock. If this is the case (it's hard to tell without a schematic or block diagram), the 555 clock circuit supplies the clock signal to the clock device circuit. As you can see, the potential for a misunderstanding is very great, so be careful and precise in your descriptions and questions. The better the question, the better the answers.

ak

#### WBahn

Joined Mar 31, 2012
26,398
So I am trying some new ideas in a few areas.
But a stumbling block that always hits me is voltage loss or amperage loss or gain loss... im not sure which.

But lets say you have a 555 timer and you want to use it as the clock.
And you want to run 1 decade off of it, that uses 4 numbers and counts to 9999 using 4 subsequent decade counters...

Logic says.

555 timer clock powers decade timer
Herein lies your problem -- you are using a logic signal to provide power to another chip. Logic signals are intended to be just that -- signals. Each chip has power supply inputs (power and ground) that are intended to be tied to just that -- power and ground. They then respond to the signals applied to their signal inputs.

Please supply a sketch of how you are actually connecting things and then we can point out what you are doing right and what you are doing wrong.

Thread Starter

#### Andrew Burke

Joined Jan 26, 2016
28
Thanks, Ill give you a sketch later. I appreciate the response, just not at home atm

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