• 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.

CD4026 IC become very hot

MacIntoshCZ

Active Member
* Note. Unless properly debounced, pressing the clock button will generate more than one increment pulse. That's what the 555 timer chip in some of your reference circuits does.
Use this, dont have time sry
100n 10k, just random values
1612171682108.png
 

Fintek

New Member
FYI if anyone is still looking at this.....

I have had the same issue. The chips are labeled from Texas Instruments, and I have tried 5 so far...all do exactly the same as the original post. One popped on the breadboard while triggering the reset pin, another got super hot, but I cut power before it fried.

I bought them from Amazon.

I am going to run some tests on another tomorrow, no load...low power (5v) and see what I get out of each pin.

It's odd that most of the schematics/ videos/ guides show no transistors/resistors at all between the output pins and the display.... someone got it working this way (maybe not for long). example: https://circuitdigest.com/electronic-circuits/555-timer-seven-segment-counter-circuit

And before you ask....I am not new at this, but I can't get this circuit to work either. I am assuming the chips are bad, or the schematics on the web are wrong.
 
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
FYI if anyone is still looking at this.....

I have had the same issue. The chips are labeled from Texas Instruments, and I have tried 5 so far...all do exactly the same as the original post. One popped on the breadboard while triggering the reset pin, another got super hot, but I cut power before it fried.

I bought them from Amazon.

I am going to run some tests on another tomorrow, no load...low power (5v) and see what I get out of each pin.

It's odd that most of the schematics/ videos/ guides show no transistors/resistors at all between the output pins and the display.... someone got it working this way (maybe not for long). example: https://circuitdigest.com/electronic-circuits/555-timer-seven-segment-counter-circuit

And before you ask....I am not new at this, but I can't get this circuit to work either. I am assuming the chips are bad, or the schematics on the web are wrong.
I suspect there are two mains options:

1) It's really poor having no limiting resistors, so the circuits are designed to overload the chip.

2) It's a fake chip from China, presumably they came from Amazon Marketplace, and not actually Amazon?.

Just checked on Amazon - the supplier I found there is:

  • JinPingQu DaXueLu TuoXinErXiang 4Hao 5Lou501
  • ShanTouShi
  • GuangDongSheng
  • 515000
  • CN
So probably fake chips - contact them or Amazon and get a refund.
 

Fintek

New Member
Yep. They're bad for sure. I set it up with no display and just checked for voltage at the output pins and only the B output showed anything. Tried the reset pin... no change. I used a regulated 5v supply and antistatic precautions. It was the same result as the other 5x.
I'm returning them today.

I am ordering some directly from Texas Instruments for only $1 more than Amazon.
I'll post how those work in a few days.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Yep. They're bad for sure. I set it up with no display and just checked for voltage at the output pins and only the B output showed anything. Tried the reset pin... no change. I used a regulated 5v supply and antistatic precautions. It was the same result as the other 5x.
I'm returning them today.

I am ordering some directly from Texas Instruments for only $1 more than Amazon.
I'll post how those work in a few days.
Examine the printing on the chips with a good magnifying glass, or microscope - you'll probably be able to see that the original chip number has been removed, and reprinted with a fake number.

Have you been asked to return them?, usually they simply give you credit and you throw them away - do you really want to post them back to China?.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
No one has mentioned these:
*CMOS inputs MUST be tied to Vcc or Ground. Choice is usually lowest power dissipation.
They will oscillate and get hot.
*Bypass caps - 0.1 uf Ceramic usually near power supply pins.
*Solderless breadboards cause problems in some circuits due to stray capacitance.
 

audioguru

Well-Known Member
Most Helpful Member
Why do people buy cheap fake ICs from an online clothing and kitchen appliances store ?
 

Fintek

New Member
Yes, they want them back, but its a free drop off at a UPS store. Funny thing though, the first order was lost/delayed so I ordered a new bunch, they refunded me for the first order, then both came in the mail. So I had quite a few to experiment with.

Yes I have pull down resistors to ground on all inputs. It did not get hot this time, it just didn't work(I tried two different chips..one from each order).
All of them do the same thing, only the led segment B output shows a voltage, including the non-breadboard circuit I originally made using a 16 pin socket and installing the chip after assembly to not overheat/static it with the soldering iron. Count or Reset HIGH changes nothing. Thats about 8 chips now, three different people making the circuit, two different breadboards, one completed circuit on stripboard, three different drawings of the same schematic. Other people on the internet are throwing this circuit together with bubblegum and bailing wire and it works just fine. I'm done with it until the Ti chips come.

But I would suggest to anyone making this circuit to either use a low power consumption display or add transistors/resistors to the output to help decrease the chips heat...just in case.
 

Fintek

New Member
Why do people buy cheap fake ICs from an online clothing and kitchen appliances store ?
Usually I don't, but I am working on a time sensitive project and wanted them quick. Amazon Prime should have gotten them to me fast (it didn't). It was to replace a counter module I already had that failed due to a bad internal battery. I just need to get this done before the Florida rainy season starts. (It is for a rainwater pumping system that is ready to go. Except for this one circuit that shows how many cycles it has run).
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Usually I don't, but I am working on a time sensitive project and wanted them quick. Amazon Prime should have gotten them to me fast (it didn't).
Presumably Prime wasn't an option as it's most likely a Chinese company using Amazon Marketplace?.

But as for delivery speed, don't Digikey etc. deliver next day? - certainly over here RS Components orders come next day pretty well without fail, even if you don't order until early evening. In fact RS are usually faster than Prime - usually the RS parts come around 8:00 in the morning, and Prime not until the afternoon, and often the late afternoon (or don't come at all as we're shut before they turn up).
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I'm with Nigel.. I get some of my stuff from Rapid-online.. CD49026BE are 34p ea.. I know delivery costs but you can get the 555 and the 7 seg display as well All for under a quid...
As long as you've got an RS account postage is free, and we do have an account - and get RS deliveries most days :D
 

Fintek

New Member
Hmmm. I'm in Florida, most places charge at least $7 for shipping, usually by UPS, FedEx, or DHL and it takes 5 days or so. The US is more costly and slower than the U.K... except for Amazon usually. (I am 2 miles from an Amazon warehouse and delivery airport.)
 

shokjok

Member
I agree with target1plus on the 330-ohm resistor selection. A single 330-ohm resistor can't handle the current from multiple lit segments. Separate 330-ohm resistors will work and not overheat the CD4026.
I don't have a CD4026 in my collection, so I'll try a CD4543 and CD4553 with 330-ohm resistors and a DL747 0.6" LED display.
 

Fintek

New Member
BTW... The Texas Instruments chips came, and they work perfectly. The other ones were defective... both packs, all 30 of them.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
BTW... The Texas Instruments chips came, and they work perfectly. The other ones were defective... both packs, all 30 of them.
Did you closely examine the chips as I suggested in post #45?.

You can usually see where the previous label has been removed, and the new one printed on - compare them to the real chips you now have.
 

unclejed613

Well-Known Member
Most Helpful Member
one test for fake chips is to use acetone on a cotton swab, and see if the printing comes off... if it does, it's a fake.... if the top surface looks like it's been run across a sander or polisher and then sometimes painted black, it's fake (in many cases the top surface isn't level or it's got a curve to it from uneven pressure on the sander)...
 

EE World Online Articles

Loading
Top