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Replace 4553 and 4543 in counter circuit

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clickshe

New Member
This new thread has been split off from this old thread:
http://www.electro-tech-online.com/threads/push-to-make-555-4026b-7-seg.147373/
JimB - Moderator



Hello, this is my first post.
I hope this is not the wrong section of the forum, but I think I can connect my question to this post because the topic appears to be similar ...

Sorry, I'm here to ask for help.

I need to modify a circuit schematic because the CD14553 and CD14543 are not more available on the market.

Around there are a lot of schematics that use the CD4026 as 'all in one' counter and decoder,
but I'm not able to replace, with operational certainty, the 14553 and 14543 using the 4026 (or, perhaps, CD4033 ?).

Below you can see the schematic that I need to adapt, leaving in their place, the two display, the 555 and the 4093.
I need to replace only the 4553 and 4543, and, possibly, I do not know if it is necessary,
to recalculate or delete the resistors and the two transistors.

Speed Indicator_.gif

Kindly, could someone help me rewriting the schematics or or suggesting an identical alternative?


I need to realize this PCB, you could suggest even a cheap chinese PCB board that do the same-identical work
and that accept external trigger input as in the schematic.
If you need more infos ...I'm here.

Thank you for reading.
Regards.
 
Last edited by a moderator:

AnalogKid

Well-Known Member
Most Helpful Member
I really liked the 4553; too bad its gone. There are some specialty distributors that might have some. Where are you?

Also, you should start your own thread. You can put a link to this thread in the post for context. The moderators can help.

ak
 

Colin

Active Member
"4026 is not really built to drive displays directly."

That is exactly what it is designed for.
 

AnalogKid

Well-Known Member
Most Helpful Member
"4026 is not really built to drive displays directly."
That is exactly what it is designed for.
No, it isn't.

According to the datasheet, typical output current with a 10 V supply is less than 3 mA. Back when this part came out, LED displays were not as efficient as they are today; that was not nearly enough for good visibility in something like an office environment, despite a line on the first page. More importantly, the datasheet has five examples of how to drive a display, and all five of them use segment drivers.

ak
 

Colin

Active Member
AnalogKid
I have sold over 1,000 kits using the 4026 to drive the displays directly, so you have no idea what you are talking about. In fact they drive the segments TOO HARD and a small current limiting resistor is needed. Don't make comments about things yo know nothing about. You have done it so many times.
 

AnalogKid

Well-Known Member
Most Helpful Member
You are dependent on the kindness of strangers. Abusing a component beyond its documented parameters 1,000 or 1,000,000 times means that the component has some operating margin designed in, not that abuse is a good design practice. It is not.

http://www.ti.com/lit/ds/symlink/cd4026b.pdf

ak
 
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clickshe

New Member
Hello everyone,
Also, you should start your own thread. You can put a link to this thread in the post for context
If there are no problems, I prefer to keep alive this post... otherwise I am ready to cancel everything and move to another thread.

EDIT
thank you moderator for "cleaning" the discussion... END Edit

I'm from Italy, I found some foreign distributors that have some 4553 and 4543, but the cost is impressive and I have to add also shipping cost.

I have not yet figured out whether it makes sense to use a 4026 or if it is better to look for another solution.
Looking at the datasheet of 4026, I do not know what to connect, according to my diagram above, to pins 2, 3, 4, 14 of 4026.
Furthermore, it seems that the 4026 does not have the "Latch Enable" taht in 4553 corresponds to the pin 10.
 
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AnalogKid

Well-Known Member
Most Helpful Member
CD40110 is a current part ($1.50 US) and has an internal latch, so it is a better single-stage replacement for the 4553. Also, unlike the 4026, the 40110 is designed to drive LED segments directly. The segment outputs are characterized differently from the other outputs, with sinking currents up to 25 mA.

The new circuit will be a significant edit, but in the end it still will be a 2-chip solution with 7 more segment resistors.

ak
 
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clickshe

New Member
Hallo
thank you AnalogKid for suggestion about cd40110.
Test_01_.gif
I tried to edit the schematic, but it certainly is not yet complete.
I need help to identify any errors, also I do not know if (or how)
pins 9, 7, 4 of both 40110 (but also other pins), and the common cathodes of the display are correctly connected.
I think, but correct me if I'm wrong, that the resistors to the display may remain unchanged because the common cathode display that I've used, require 20 mA.
I use DipTrace to draw schematics, so I can send or accept .dch file

If someone wants to compare the initial/original schematic with this one, and report errors, I would be very grateful.
Again, thanks to all.
 
Last edited:

AnalogKid

Well-Known Member
Most Helpful Member
All inputs of both chips must be connected to something, depending on their function. Also, don't you want both chips to latch at the same time?
For the display resistors, 470 ohms will get you about 20 mA of segment current.

ak
 
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