555-4026b-7segment Counter Circuit.

[John Murdock]

So.

I have started a project on creating circuit that would be able to count money that I could use. The circuit would be able to count from 0-99
A circuit very much similiar to it can be seen here: **broken link removed**

1)
Onthis link you can see a circuit with one segment requiring one 4026b and one 555. I have created the one under with 2 4026bs 2segment displays and a 555. What I do not understand is how this 555 starts or how it functions or why it is needed. I know how the segment display and the output pins of the 4026b work but nothing else.

2) How would i be able to have it count up to 999, how would i connect the 4026b ICs?

3) would using a piezo transducer or a push to make be better for a coin dropping on it. I believe a piezo would be better unless there are better options..


Interms of components or alternatives shout out anything I Pretty much have access to any kind of component.

Thanks all.

 

[Les Jones]

Hi John,
1/ I cannot see any 555 in the link you posted so I do not know what you mean.

2/ You can count to as many digits as you want. all you need to do is connect the CO (Carry out.) pin of the first digit to the CLK (Clock) input of the second stage. Connect the CO (Carry out.) pin of the second digit to the CLK (Clock) input of the third stage and so on.

3/ You would need something more complex than just a simple sensor to detect coins. It would need to check som physical properies of the coin to confirm that it is a genuine coin of the correct denomination.

If I was doing this I would probably use a micro controller rather than anumber of 4000 series ICs.

Les.

 

[spec]

Hi John,

Welcome to ETO

So.

I have started a project on creating circuit that would be able to count money that I could use. The circuit would be able to count from 0-99
A circuit very much similar to it can be seen here: **broken link removed**

1) On this link you can see a circuit with one segment requiring one 4026b and one 555. I have created the one under with 2 4026bs 2segment displays and a 555. What I do not understand is how this 555 starts or how it functions or why it is needed. I know how the segment display and the output pins of the 4026b work but nothing else.

Firstly, the 555 is just a free running oscillator which generates a constant train of pulses. The rate of the pulses from the 555 can be adjusted by altering the values of certain resistors and capacitors in the 555 circuit. The 555 is just used to cycle the counter through its counts. It is used for testing and would not be part of your final circuit.

2) How would i be able to have it count up to 999, how would i connect the 4026b ICs?

You have already connected two counter chips together to count up to 99. Simply add a third chip connected in the same way as the first two, to count up to 999.

3) would using a piezo transducer or a push to make be better for a coin dropping on it. I believe a piezo would be better unless there are better options..

There are many ways of providing a clock input to the three digit decimal counter that you will have made. A switch would be the simplest. But if you use a switch you will need a debounce circuit, because when you close a mechanical switch the contacts bounce rapidly for a short period. This bouncing would trigger the clock of your counter and give you multiple counts, when all you really wanted was a single count.

I will put together a circuit for you to make matters clearer.

spec

(our posts crossed Les)

 

[John Murdock]

Thanks Spec that would be awesome! (thanks for welcoming me!)

Les thanks for the help!.

I have the circuit on circuit wizard but I am unable to put it up here through 'upload a file' so I'lljust go with Spec and see what goes..

 

[John Murdock]

Hi John,


3/ You would need something more complex than just a simple sensor to detect coins. It would need to check som physical properies of the coin to confirm that it is a genuine coin of the correct denomination.

If I was doing this I would probably use a micro controller rather than anumber of 4000 series ICs.

Les.

I'm not the greatest with Pics and all that but if I were to make a start on that were would you suppose I begin regarding this input.

 

[spec]

HI John,

No probs

Here is the circuit for the three digit decimal counter.
I will post a circuit for a switch input to clock the counter shortly.

 

[John Murdock]

Thanks you have been a great help!

Since the 7 segment goes to ground I believe that it is a common cathode?

 

[spec]

Here is a circuit so that when the switch is closed the counter will be clocked once.
When the switch is open nothing will happen.
After a delay of about a second, if the switch is closed again the counter will be clocked again.
This circuit is a bit crude. Later we can do a Rolls Royce version, but this will do for testing
The capacitors across the 6V supply rails are for decoupling. The big capacitor decouples low frequencies and the smaller capacitor decouples high frequencies. You decouple to supress noise on the supply lines which may interfere with the correct operation of your circuit, especially as the displays will be drawing relatively large gulps of current from the 6V supply rail.

ERRATA
(1) put a 47R resistor in series with the top of the switch and the 6V supply rail

 

[spec]

Thanks you have been a great help!

Since the 7 segment goes to ground I believe that it is a common cathode?

My pleasure John.

Yes those 7 segment displays look like common cathode. I will investigate and see exactly what is going on with the drive to the seven segment displays. Do you have the part number for the displays that you are going to use?

Cheers

spec

 

[spec]

Hi again John,

You mentioned that you can't upload files at the moment so try this:

In your posting window if Upload File is not showing, lclk More Options to open a bigger window with an upload file option.

If you are unable to see the files on your computer that you want to upload you need to unckeck 'Enable Adobe Flash Protection Mode' in your browser.

I only know how to do this in Firefox:

Tools> Add-ons>Plugins: lclk on Shockwave Flash, uncheck Adobe Flash protected mode.

Turn browser off and on

spec

 

[AnalogKid]

For a 3-digit up-counter, keep it simple. The MC14553 is a 3-digit counter, latch, and display multiplexer in a single chip. Here is a typical schematic.

https://www.kitsrus.com/pdf/k1.pdf

ak

 

[spec]

For a 3-digit up-counter, keep it simple. The MC14553 is a 3-digit counter, latch, and display multiplexer in a single chip. Here is a typical schematic.

https://www.kitsrus.com/pdf/k1.pdf

ak

Neat AG, but 2 chips, 4 transistors, 1 diode and 10 resistors is more complex than three chips and 3 resistors. The operation is also more complex to understand for the OP who says he is no expert. Also the design is less scaleable. On balance, I would suggest that the original circuit is better in this case.

 

[AnalogKid]

To the OP: The site linked in your first post has a fundamental design flaw that stresses the 4026 chip beyond its specified operational limits.

spec - depends on what you mean by complex. First, the circuit in posts #1 and #6 are missing 21 current limiting resistors to protect the 4026 output stages. They depend on the the P-channel output transistors to act as both current limiting and balast resistors for the individual display segments, something they never were intended to do. Second, the outputs are rated for under 5 mA per segment max and 3 mA typical, which will limit significantly the display brightness. Third, at those output currents the output voltage will not be close to the rail, which will decrease display brightness even more. There are five different display applications in the 4026 datasheet, and *none* of them have the device directly driving anything except other display driver devices. Why do you suppose that is?

Fourth, what is the purpose of R1 at each display? If it is meant to be an overall current limiter, that will not work. There are several threads on this and other sites that explain why driving LEDs that are connected in parallel will not work, and that is essentially what you are trying to do. The display brightness will vary greatly depending on how many segments are lit. Also, when multiple segments are lit they will not be at the same brightness because the LEDs will not have perfectly matched forward voltages. Separate from that, with 6 V Vdd and 2.0 V Vf for an LED display segment, then a perfectly saturated output limited by only 100 ohms would have to supply 40 mA, while all of the charts for the high output condition quit at 30 mA. More importantly, while there is no plot for Vdd = 6 V, at 5 V the device can supply less than 5 mA. Most importantly, that is at an output voltage of zero volts, the exact opposite of saturated. In other words, the device cannot directly drive the display effectively or reliably, with or without current limiting resistors to keep it from burning up.

OTOH, the 4511 suggested in post #11 is designed from the ground up to be an actual display driver, and can source 25 mA while maintaining a terminal voltage high enough to drive an LED display with headroom to spare. This is more than enough current for visibility in anything other than direct sunlight.

When comparing different designs, one way to judge the complexity of a project is by the total number of soldered device pins; another is by the total circuit power. For anything with a multi-digit display, multiplexing wins every time.

ak

 

[4pyros]

How is this for low parts count?
**broken link removed**

**broken link removed**

 

[John Murdock]

analogkid you sound like you know your stuff!

They are missing resistors you are right. I bread boarded the circuit and soon realized that they were necessary. The link I have attached is merely what I have based the circuit of my project on. Infact initially the first circuit that I made was using a 4511 Ic which from what I hear seems to be a lot easier.. I'll breadboard the circuit you have but first i will check it out on software. I normally use circuit wizard but it does not have the ICs that are shown in your link, do you recommend or know any other one I could use!

 

[John Murdock]

Hi again John,

You mentioned that you can't upload files at the moment so try this:

In your posting window if Upload File is not showing, lclk More Options to open a bigger window with an upload file option.

If you are unable to see the files on your computer that you want to upload you need to unckeck 'Enable Adobe Flash Protection Mode' in your browser.

I only know how to do this in Firefox:

Tools> Add-ons>Plugins: lclk on Shockwave Flash, uncheck Adobe Flash protected mode.

Turn browser off and on

spec

Thanks for that again! I will upload a picture of the circuit when I have completed it.

Interms of the part number for the IC I could send it to you tomorrow since I'm already home and away from my working materials

What program did you use to design the de-bouncing circuit and the main circuit? it looks very familiar.

 

[John Murdock]

How is this for low parts count?
**broken link removed**

**broken link removed**

Simple and does the job, I'll have a crack at that aswell!

 

[spec]

To the OP: The site linked in your first post has a fundamental design flaw that stresses the 4026 chip beyond its specified operational limits.

spec - depends on what you mean by complex. First, the circuit in posts #1 and #6 are missing 21 current limiting resistors to protect the 4026 output stages. They depend on the the P-channel output transistors to act as both current limiting and balast resistors for the individual display segments, something they never were intended to do. Second, the outputs are rated for under 5 mA per segment max and 3 mA typical, which will limit significantly the display brightness. Third, at those output currents the output voltage will not be close to the rail, which will decrease display brightness even more. There are five different display applications in the 4026 datasheet, and *none* of them have the device directly driving anything except other display driver devices. Why do you suppose that is?

Fourth, what is the purpose of R1 at each display? If it is meant to be an overall current limiter, that will not work. There are several threads on this and other sites that explain why driving LEDs that are connected in parallel will not work, and that is essentially what you are trying to do. The display brightness will vary greatly depending on how many segments are lit. Also, when multiple segments are lit they will not be at the same brightness because the LEDs will not have perfectly matched forward voltages. Separate from that, with 6 V Vdd and 2.0 V Vf for an LED display segment, then a perfectly saturated output limited by only 100 ohms would have to supply 40 mA, while all of the charts for the high output condition quit at 30 mA. More importantly, while there is no plot for Vdd = 6 V, at 5 V the device can supply less than 5 mA. Most importantly, that is at an output voltage of zero volts, the exact opposite of saturated. In other words, the device cannot directly drive the display effectively or reliably, with or without current limiting resistors to keep it from burning up.

OTOH, the 4511 suggested in post #11 is designed from the ground up to be an actual display driver, and can source 25 mA while maintaining a terminal voltage high enough to drive an LED display with headroom to spare. This is more than enough current for visibility in anything other than direct sunlight.

When comparing different designs, one way to judge the complexity of a project is by the total number of soldered device pins; another is by the total circuit power. For anything with a multi-digit display, multiplexing wins every time.

ak

Nice work AG,

I had not analyzed the circuit of the OP web link at the component level. Instead I did a system level design as requested. It just goes to show you can't always trust everything you see on the net.

spec

 

[spec]

Thanks for that again! I will upload a picture of the circuit when I have completed it.

Interms of the part number for the IC I could send it to you tomorrow since I'm already home and away from my working materials

What program did you use to design the de-bouncing circuit and the main circuit? it looks very familiar.

No probs John,

The main circuit was done in Microsft Word, using the Draw (Add Objects) functions. The single stage counter was screen captured using SnipIt as a .png file from the site you mentioned. That was then pasted three times on to a Word page which had been loaded with a drawing canvas. The clock lines were then drawn in with the Word Draw line function. The final circuit was then captured by SnipIt again and the resulting .png image posted on ETO. Looks like quite a procedure when written up but it is quite simple really, once you have done it a few times.

The switch debouncing circuit was done in EAGLE 7.5 LITE ECAD, which is free for private use. I previously used high-end ECAD at work and had a home license too, but after retirement I lost the home license and have recently moved to EAGLE, and have found it simple to learn and use, but I have only done circuit capture with it so far.

spec

 

[spec]

Just to put another iron in the fire, I wounder if an LCD version of the counter would be worth considering- it would certainly use less power
spec