Problem with 555+4017 circuit (LEDs always on)

[ccurtis]

So, the question remains. Why are the OPs LEDs dimly lit when they are expected to be off?

 

[Mikebits]

I dunno, the TI data sheet for the 4017 kinda sucks. As a production designer you have to assume worst case to ensure your design will work in large production runs. The data sheet table shows very low IOL specs as typical, the graph shows a different picture.

If you go by the data sheet typical spec in the table, your not gonna drive an LED very well, if you go by the graph then your okay. After sitting through many engineering design reviews I have learned that design by possible maxima is bad practice, and one should design worst case. To me, this seems the way to go if you want to ensure your design will work each and every time. That is how my company has made the Fortune 500 list. I am sure my engineering reviewers of such a design that uses the graph rather than the table would scold me as this would be an unreliable design. What if certain lots land more on the low side than what is shown on graph. Seems like this part is not properly speced if it averages more on the high side of the spec. I like how the data sheet shows a - for maximum...

I think the days are numbered for the 4000 series anyways.

 

[audioguru]

I dunno, the TI data sheet for the 4017 kinda sucks. As a production designer you have to assume worst case to ensure your design will work in large production runs. The data sheet table shows very low IOL specs as typical, the graph shows a different picture.

On the datasheets from Texas Instruments there are typical graphs and minimum graphs.

10V supply, 2.0V LED without a current-limiting resistor:
Typical current = 18.5mA.
Minimum current = 9.5mA.
Plenty of current for a bright modern LED. Very old LEDs might look dim.

 

[colin55]

My white LEDs are 20,000mcd and operate on 17mA.

 

[Boncuk]

More overdesign. You wouldn't last one day in business.

I've lasted for 25 years now with overdesign. My overdesigned circuits did not fail within a 20 year period.

Just to make sure you won't miss another overdesigned circuit, here is the layout of it. (not the final version though.)

You are talking about your design, so why not post it?

The OP initially wanted to operate the circuit with a 9V/100mA battery, which is definitely too weak.

 

[colin55]

You say you are an electronics engineer. Show me where you can get a 9V/100mA battery. I want to buy one.

 

[Boncuk]

You say you are an electronics engineer. Show me where you can get a 9V/100mA battery. I want to buy one.

The 9V block battery doesn't have more than 100mA/h.

Additionally I'm not saying I'm an electronics engineer. I just said that I have been designing circuits for more than 25 years.

If you dig into ST-microelectronics data sheet of the HCF4017 you'll be amazed by the low source and sink current it can provide. At VDD=10V it can source and sink 0.9mA which increases to 2.4mA at VDD=15V. (The OP wants to use a 9V battery, so the current output is even worse.)

It's poor design from my point of view to hook up an LED directly to an output pin of that counter.

Try this and experience a surprise: Drive an LED and use the same pin to control another CMOS-logic device. The LED will stay on, but the device won't react the way you expect.

Boncuk


P.S. I haven't seen your design yet.

 

[ccurtis]

On the datasheets from Texas Instruments there are typical graphs and minimum graphs.

10V supply, 2.0V LED without a current-limiting resistor:
Typical current = 18.5mA.
Minimum current = 9.5mA.
Plenty of current for a bright modern LED. Very old LEDs might look dim.

You can expect to have up to a 9 mA current (minimum) variance from one LED to another. That is easily noticeable.

 

[colin55]

A battery capacity is not expressed as: "The 9V block battery doesn't have more than 100mA/h."

It is: 100mA-h. or 100mAhr or 100mAh There is a big difference.


You should never drive a LED directly from an output of a chip. Always allow the output to rise as high as possible to prevent overheating of the drive transistor(s) in the output.

I don't kow where you get the concept: "you can have up to a 9 mA current (minimum) variance from one LED to another." If we are talking about this sequencer circuit, this does not apply - unless you have 2 or 3 LEDs in one of the lines - but that was not stipulated.

 

[colin55]

I could not design the circuit myself as I have no ability in this field. But I have found this circuit on the web:

**broken link removed**

 

[Mikebits]

On the datasheets from Texas Instruments there are typical graphs and minimum graphs.

10V supply, 2.0V LED without a current-limiting resistor:
Typical current = 18.5mA.
Minimum current = 9.5mA.
Plenty of current for a bright modern LED. Very old LEDs might look dim.

The data sheet table and the graph seem to be in contradiction, that is why I say the data sheet sucks. It is unclear to me. The specs listed as typical in the table do not match the graph. Which one should we believe?

 

[ericgibbs]

colin55;718009]I could not design the circuit myself as I have no ability in this field. But I have found this circuit on the web:

**broken link removed**

The circuit you found on the web, just happens to be from your site, where you initially claimed to be the designer of circuits.

How is is now you admit you couldnt design a paper bag, yet you are telling qualified experienced 'real professional ' engineers they dont what they are talking about.

Cut out the nonsense and you just might learn something from other members posted replies.

 

[Boncuk]

A battery capacity is not expressed as: "The 9V block battery doesn't have more than 100mA/h."

It is: 100mA-h. or 100mAhr or 100mAh There is a big difference.

German standards say it is 100mA/h. Anyway, everbody will understand this without discussing it.

Do you have any more useful adds to this?

Still waiting for your design!

If you can't do it, why not just turn towards another threat which you might be able to answer in a qualified manner and help the poster to solve his problem.

I consider these unneccessary discussions being ended now.

Boncuk

 

[Boncuk]

If we are talking about this sequencer circuit, this does not apply - unless you have 2 or 3 LEDs in one of the lines - but that was not stipulated.

Yes, it is clearly stipulated by the animated picture showing two LEDs lit simultaneously!

RTFQ!

Boncuk

 

[colin55]

I have supplied the circuit diagram.

Show me where any authority says the capacity of a battery is measured as mA/h. This is a "flow rate" not a capacity. You don't know your terminology.

Show me the animated picture showing two LEDs lit simutaneously.

 

[audioguru]

Energizer has a datasheet for every battery they sell. They show their 9V alkaline battery with a capacity of 625mAh when the current is 25mA and a capacity of only 280mAh when the current is 500mA. A new one can easily supply 1A or 2A for a few minutes.

Duracell say that the internal impedance of their 9V alkaline battery is 1.7 ohms when new. So it will supply 4.5V at 2.6A.

The HFC4017 has exactly the same spec's as all other 4017 manufacturers. The max allowed dissipation in each output transistor is 100mW.
With a 10V supply, the output current is typically 2.6mA or a minimum of 1.1mA when the output voltage drop is only 0.5V.

The chart spec's agree exactly with the graph on the datasheet from Texas Instruments:
1) With a 10V supply and a 0.5V drop, the typical current is slightly more than 2.5mA.
2) With a 10V supply and a 2.0V LED without a current-limiting resistor the typical current is 18.5mA (but the dissipation in the output transistor is too high).
3) With a dead short the current is 19.6mA but the output transistor is dissipating nearly double its max allowed dissipation.

The IC is monolithic so the transistors match very well. There will not be much variation in current for the outputs of one IC.

I think using a single current-limiting resistor might destroy the LEDs that are turned off because they will have more than their max allowed 5V reverse voltage.

 

[Boncuk]

I have supplied the circuit diagram.

No! You just have supplied any circuit diagram, not yours!

You don't know your terminology.

You better watch your language and the selection of vocabulary!

Show me the animated picture showing two LEDs lit simutaneously.

You are not seriously expecting I take you by the hand and take you where you want to go, are you?

Just scroll back to page2 of this thread. The picture is clearly seen in the OP's
post of Mar 29.

Last not least, please cut out this nonsense as already posted here, too.

 

[ccurtis]

The IC is monolithic so the transistors match very well. There will not be much variation in current for the outputs of one IC.

The datasheet does not make a distinction between outputs on single device and outputs from one device to another. Responsible design requires documented information provided by the manufacturer for the specific device. At least two other leading manufacturers (ON semi, and NXP) do not specify Iout for greater than 0.5v output drop with 10v supply. Characteristic Vo vs. Io beyond that point is undefined. Monolithicity is not a design parameter, and is not a measure of how well transistors within a specific device are matched. How well the transistors are matched depends on several factors, such as tolerances used in the artwork, variability allowed in test and manufactering, and control of microscopic variances in the wafer.

 

[audioguru]

The datasheet does not make a distinction between outputs on single device and outputs from one device to another. Blah, blah blah.

I guess you have not tried it.
The outputs of monolithic devices are very well matched.

Responsible design requires documented information provided by the manufacturer for the specific device. At least two other leading manufacturers (ON semi, and NXP) do not specify Iout for greater than 0.5v output drop with 10v supply. Characteristic Vo vs. Io beyond that point is undefined. Monolithicity is not a design parameter, and is not a measure of how well transistors within a specific device are matched. How well the transistors are matched depends on several factors, such as tolerances used in the artwork, variability allowed in test and manufactering, and control of microscopic variances in the wafer. Blah, blah, blah.

We do this for fun, not for profit.
When I did it for profit then every single circuit worked perfectly. Now that I do it for fun, every single circuit still works perfectly.

 

[colin55]

I don't see any animated diagram on Page 2 of this thread, dated Mar 29, where 2 LEDs are illuminated.

You have still not attested the difference between 100mA/h and 100mAhr.

You can clearly see my circuit is much simpler than using 2 555's and 3 transistors. I designed this in my head before building it and all the initial values gave almost the exact timing required.

You may have to look into protecting the LEDs when the supply is 12v as the reverse voltage across each non-illuminated LED is above 5v.