Driving a 4026

Status
Not open for further replies.
W

Wokyerdog

New Member
Hey guys,

New to the forum here but i like what i see so far!

I'm somewhat new to chips n stuff but im pretty solid with basic electronics.

Anyway, I'm trying to figure out how to drive a 4026 (which in turn drives a 7 seg LED) with a rotory knob (continuous potentiometer?). I need a knob that turns infinitely in both directions to increase and decrease the numbers.

Thanks in advance

Wok
 
So you want the displayed numbers to increase and decrease as you turn the pot left and right? From what number to what number?

You're going to need some kind of A-to-D interface in front of the counter chip, like a comparator with a ladder resistor network or something. Keep in mind that the 4026 only accepts digital (logic-level) inputs, nothing really "analog".
 
You need a knob that turns infinitely? With some trim pots, once you get the the end they will keep turning but the resistance value won't change any further. I'm not aware of any pot that you can turn infinitely and change its resistance. What range of values do you want to show on the 7 segment display or displays? What is the range of input voltages? What resolution are you looking for?

As for the rest, this would be easiest to do with a microcontroller but if you want to go the logic IC route than you would need to connect the wiper of your pot to an ADC (analog-to-digital converter) IC. If you could find one that has a serial output compatible with the 4026 then great. Someone might know right away which one to use. If the ADC has a parallel output, you'll need a parallel to serial converter in between the ADC and 4026.
 
I think (but of course I could be wrong) that by "infinitely" what they mean is without discrete steps, like a switch. Don't think they necessarily want a pot that turns 360° continuously.
 
You cound use a rotary encoder. They have continous rotation and a digital output that would be easy to connect to a digital circuit.
They also indicate clockwise or counter clockwise rotation.
 
Last edited:
I apologize, i shoudl have been more clear.

My intention was to have 3 4026 IC's power 3 7 seg LED displays. (I think that's what's required). so the numbers would go 1 - 999. The knob, im my mind, is the same thing that u use on newer radio or stereo receiver to adjust the volume. As you turn it you can feel the steps. So in my circuit, as I turn it, the display woudl increase 1 number at a time as well as decrease when turned the opposite way. I'm not really sure what the component would be for the knob. I thought it was the continuous potentiometer but im thinking this was incorrect. From what i understand about the 4026, it jsut needs a pulse, say from a tactile switch, into the input to advance the number.

As far as the other chips mentioned, it's beyond my understanding at this point. I'm looking up new chips everyday but all the info is overwhelming, lol. I jsut wanted to start with this seemingly basic circuit and go from there.

Thanks guys

wok
 
Last edited:
As Brevor stated you could use a rotary encoder such as this (buy at Digkey for example) with a quadrature decoder (second circuit) to get the up/down pulses for the display.

The display counter needs to be an up/down type such as the CD40110. The 4026 only counts up.

Edit: If you want to avoid underflow and overflow on the minimum and maximum counts you will need to add AND and/or NOR gates to detect the minimum and maximum count values, and stop the count at that point (inhibit the count in that direction).
 
Last edited:
You probably don't need a ADC (analog-to-digital converter) because what you really want, as Brevor explained, is a rotary encoder. This is actually a switch, with a number of positive detents (places where you feel a "bump" as you turn it) that generates pulses as you turn it.

I have no idea how to interface this, but it shouldn't be all that difficult. Everything should be in the "digital domain", as they say.

Edit: I see Carl beat us all to the punch here.
 
Last edited:
I think you're barking up the wrong tree with the 4026, it only counts up. The 40110 however, is an up/down display driver.
*caveat: I've not read the entire thread properly. (just skimmed it).

Edit: I've just noticed crutschow's post. Oops (mental note: read the entire thread properly before posting)
 
Last edited:

That sounds like the perfect part, much smaller than I remember. Only problem with datasheet is figuring out the physical pinouts, ie. which pin is phase A?
 
Mikebits said:
That sounds like the perfect part, much smaller than I remember. Only problem with datasheet is figuring out the physical pinouts, ie. which pin is phase A?
Click to expand...
If you are referring to the Panasonic encoder, figure No. 2 of the data sheet shows Phase A on the left, facing the shaft.
 
carbonzit said:
I think (but of course I could be wrong) that by "infinitely" what they mean is without discrete steps, like a switch. Don't think they necessarily want a pot that turns 360° continuously.
Click to expand...

That makes more sense then what I was thinking.

As for the other stuff, the rotary encoder idea is a good one. If you're dead set on using just one knob, it can be done but the easiest thing in my opinion would be to have one rotary encoder per digit. So the first one would set the 1's place, the second the 10's, and the third the 100's. Then you could use a BCD to 7 segment encoder like the **broken link removed** to drive each display. You would essentially be making 3 copies of the same circuit.
 
All good stuff guys. Thanks for all the help so far! I'm sure that there will be many more questions as i am still very new to this stuff.

I think for the encoder that I would be able to canibalize a mouse wheel. I took one apart yesterday after reading your posts and looking at that data sheet for the encoder and I believe that a cheap mouse wheel uses a rotory encoder. Wether or not it will work in my application is still TBD. I'm assuming it will but i just wanted to run it past you guys first.

2nd concern is what pin does what? the datasheet gives physical dimensions but im not sure what the 5 pins are for.

-wok
 
Are you sure the mouse wheel is a rotary encoder? I would have just thought it senses direction.

EDIT: Never mind. I thought you were going to use something like this:

Rotary Switch

But I see what you're after now.
 
Last edited:
the rotary encoder. Unless im looking at the datasheet wrong, i thought i saw two pins on the side of it and 3 pins in the front.
 
There are 3 electrical pins (A out, B out, and common. See figure No. 2.). The other two are just mounting tabs if it's mounted on a PC board.
 
If you want to get fancy, the encoder could vary one digit and then a press move it to a second digit etc. Fancier yet, the selected digit blinks.
The advance knob is the built in push button switch in the encoder.

crutschow:

Since your not contactable via PM or otherwise, I just have to say this: Every time I read one of your posts, I swear I'm reading the comic strip.
i.e. The avatar you selected really suits you.
 
Last edited:
Status
Not open for further replies.

Similar threads

  • Question
Driving Transformer Help
Replies
14
Views
1K
Athosworld
L
Controlling a Stepper Motor Valve with a DAC
Replies
4
Views
2K
Lapinrose
L
V
  • Question
Convert a single-phase motor to a three-phase
Replies
4
Views
1K
ZipZapOuch
J
  • Question
Testing a Capacitor Microfarad Rating that has a Resistor
Replies
7
Views
2K
Tony Stewart
N
  • Question
Current draw from a Fridge compressor circuit
Replies
0
Views
56
NorthernGuy
N
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…