Hi, i am trying to get a 7-seg LED display to count from 1-9 using a 555 timer and a 4026 decade counter/display driver, i have wired up the circuit and have tried various things (adding connections, moving connections etc) and got some slightly different results...
i got
-number 6 constantly on
-number 6 flashing on and off (with the pulse of 555 timer) when the 6 went off, the middle light (g) was on
-number 1, number 2 with g missing, back to front 3, 4 with g missing, 5 with a few missing and so on.

could it be because i am using a cathode LED display and not annode?

Thanks,
Mike

 

There is not much to go wrong with this combination. Could you provide a schematic or wiring diagram of what you have?

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hi, this is what i was following: http://555-timer.clarkson-uk.com/projects/dice.html

but i had a different timer circuit (which was giving a pulsing output) i have just tried a different circuit with just 6 LED's and it didnt work.... i then realised i was using a 14 pic 4017 instead of a 16 pin!!! i replaced it with a 16 pin and it worked so i will try again now and let you know how i get on.

Thanks
Mike

EDIT: sorry, that is a different circuit.... got confused because i was trying 3 or 4 counting circuits with both LED's and the 7 seg counter.

I dont have a schematic or wiring diagram but i used this: http://www.kpsec.freeuk.com/components/cmos.htm#4026

i had the reset to the negative rail (0v)
disable clock- 0v
enable display- +6v
i tried the not 2 output in +Vs and 0v

also, each output to the corrosponding input on the 7 seg display

 

Well, I am confused. In your first post you said you are using a 4026, now its a 4017 (the famous Led-chaser IC, which, to my knowledge, only comes in 16 pin version).

If you are looking for a circuit that displays the next number in sequence (0-9) each time the 555 pulses, you want a binary counter chip. For that, I use the 74LS90 with great success. Of course, then you must use a 74LS47 or 48 to drive your seven-segment display.

If you want to do this in CMOS, you can use the 4029, which is a counter-driver chip.
Edit: Sorry, wrong number. It IS the 4026 that drives seven-segment. Also, I see you have edited your post while I was creating mine. Make sure you are wired correctly. Your circuit should work.

I have attached a schematic of a basic counter circuit if you want to see how I do it.

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sorry, the 1st part of the 2nd post was for a different circuit.... i am using the 4026 (counter + display driver)

page 5 here: http://www.qkschool2.org.uk/keys/tec...5devices2c.pdf is what i used but made a few changes to the timing part the 4026 was wired the same but i am only using 1 display (counting from 0-9)

 

i have tried several times and so has our electronics teacher and neither of us can get it working.... i NEARLY got numbers at one point... my teacher thinks it is because we are using the cathode display but if all the lights light, it cant be can it??

 

Good morning (here),

Apparently we are cross-posting. That is a viable circuit you are working from. Make sure pin 3 of the 4029 is held high. Also, I have found that putting a 100 uF cap between pos and gnd of your circuit often solves these little problems.

Good luck.

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pin 3 is high and i tried the cap but no luck

i now get output g on the 7 seg display (pin 7 on the 4026) flashing but nothing else, i get this with or without the cap

What should pin 4 be (enable out) at the moment, i have it to the +Vs

 

Is your circuit built on a breadboard so that you can re-arrange part easily? If so, put an LED and resistor in series between pin 3 of your 555 and ground. This will determine if your 555 is delivering an appropriate signal. Let me know.

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that is what i did, and yes it is delivering signal.... i am uploading a video to show you what happens.

i got those "attempted numbers" again

 

sorry about the poor quality. (click to play)

 

Hmmmmm.....

Thanks for the video. I can see the timer is working properly. The counter is obviously changing state with each pulse... assuming the 4026 is behaving properly,the problem must be in the display section. Double and triple check your connections between the driver and 7-seg. Make sure the 7-seg is not "upside down". The circuit you are going by calls for a common cathode display, so you are okay there. You'll solve it, eventually.

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it may be annode then.... not sure though.... i remember the teacher saying that something says you need anode or cathode and he ordered the wrong one.

i think it is anode because in the magazine it said cathode 7 seg sisplays but on the datasheet it was anode

the part # is SA04-11HWA

 

And therein lies your problem, I think. The 11HWA, according to by documentation, is a common anode. The 12 HWA is the common cathode.

Since the 4026 outputs a "high" to the 7-segment, the cathode of each segment's diode must be grounded, exactly like you would ground an LED.

I'm sure, if you get a common cathode display, your problem will be solved.

Have a nice rest of the day.

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our teacher said he will order some soon.

Thanks for your help

Mike