4 digit display help

I’m new to electronics, first time working with them. I already have done lighting up the led and have done a push-button switch.

I was wondering if i could get some help with the 4 digit 7 segment display. I saw how to hook up a single digit display, and i hooked my 4 digit display up the same except making adjustments for the increase in pins. I didn’t hook it up yet cause idk if i could possibly damage my board or not.

Here is the spec sheet. Though it’s for the green one i believe. http://www.jayconsystems.com/fileuploader/download/download/?d=1&file=custom%2Fupload%2FFile-1341357035.pdf

I attached a picture of my wire setup.

rockstar8577: i hooked my 4 digit display up the same except making adjustments for the increase in pin

Sounds like a wise move, but rather pointless. You might try checking here

http://playground.arduino.cc/Main/MAX72XXHardware

As you appear to have nothing like it. There are other methods, but this is about as simple as you can get.

A smaller and clearer picture that is more representative of what is happening will get a better response.

The data sheet you show may have a slight difference in the electrical characteristics.

Nick_Pyner:

rockstar8577:
i hooked my 4 digit display up the same except making adjustments for the increase in pin

Sounds like a wise move, but rather pointless. You might try checking here

http://playground.arduino.cc/Main/MAX72XXHardware

As you appear to have nothing like it. There are other methods, but this is about as simple as you can get.

A smaller and clearer picture that is more representative of what is happening will get a better response.

The data sheet you show may have a slight difference in the electrical characteristics.

Would you care to elaborate on the wise but pointless?

How would that guide help?

Smaller and clearer? Want me to rearrange the wires

I don’t think the data sheet would have any differences just because they link the same data sheet for all 4 displays. I’m just not sure on my display because i got it in a kit. Here’s a link to their page with the 4 digit displays.
http://www.jayconsystems.com/js-arduino-starter-kit-intermediate.html

rockstar8577: Would you care to elaborate on the wise but pointless?

You say you wired individual digits the same. This means you will have four digits displaying the same, rather than their own, data. However you also appear to have paid attention to the current requirements, thereby engaging on a pointless exercise, but not fatal.

How would that guide help?

Don't ask, just read. If it's not particularly relevant now, it will be soon.

Smaller and clearer? Want me to rearrange the wires

At the moment you have a huge picture that takes time to load and is tedious to view. Those silly enough to wait eventually find it says nothing, which is likely to piss them off mightily. When a wire disappears under a display, who knows where it's going? and those that don't know are not likely to care. You might have a better time of it if you just move the display down one row. A $2 kit of jumpers would give you some more colours. You won't regret that.

I don't think the data sheet would have any differences just because they link the same data sheet for all 4 displays.

There may be minor differences in forward voltage with different colours, hence different current limiting resistors. I don't think this is particularly critical, just something you ought to be aware of.

Where are your current limiting resistors?

It looks like you are trying to drive all four of your characters at the same time instead of multiplexing them. Have you considered what the current draw would be (even if you did have the correct current limiting resistors installed) if you tried to display 8 8 8 8 ?

Download a copy of the ATmega328 datasheet, find Table 28-1 and then look at notes 3 and 4 that follow the table.

Don

You say you wired individual digits the same. This means you will have four digits displaying the same, rather than their own, data. However you also appear to have paid attention to the current requirements, thereby engaging on a pointless exercise, but not fatal.

Ohh i meant as in, i saw how a single digit segment display was wired. So i took that and expanded it on what i thought the 4 digit segment display should be like. If i'm correct or not, idk.

Don't ask, just read. If it's not particularly relevant now, it will be soon.

Okay will do.

At the moment you have a huge picture that takes time to load and is tedious to view. Those silly enough to wait eventually find it says nothing, which is likely to piss them off mightily. When a wire disappears under a display, who knows where it's going? and those that don't know are not likely to care. You might have a better time of it if you just move the display down one row. A $2 kit of jumpers would give you some more colours. You won't regret that.

Ohh sorry about that. When i opened it it wasnt actually huge. I did wonder on the size though, it just never struck me. I think it would be better if i did a diagram. Any software to lay it out easily?

There may be minor differences in forward voltage with different colours, hence different current limiting resistors. I don't think this is particularly critical, just something you ought to be aware of.

Ahhh okay, i didnt know that thanks.

Where are your current limiting resistors?

It looks like you are trying to drive all four of your characters at the same time instead of multiplexing them. Have you considered what the current draw would be (even if you did have the correct current limiting resistors installed) if you tried to display 8 8 8 8 ?

Download a copy of the ATmega328 datasheet, find Table 28-1 and then look at notes 3 and 4 that follow the table.

Don

I don't have any, unless it uses the onboard one, which im guessing the single digit does. I modified the single digit layout for 4 digits. Idk if i'm correct in that, it was just a thought. I didn't test it yet cause i wasn't sure if it would just blow up so that's why im asking here.

Multiplexing from my understanding somewhat comes from the code.

Though like i said in my first post, i'm new to this.

rockstar8577: Ohh i meant as in, i saw how a single digit segment display was wired. So i took that and expanded it on what i thought the 4 digit segment display should be like. If i'm correct or not, idk.

OK just make sure you are using limiting resistors. If they are not in the kit, it doesn't mean you don't need them.

it would be better if i did a diagram. Any software to lay it out easily?

Probably correct. I'm an architect so I just use my workaday CAD and I don't know about the dedicated stuff, but it is around. There is that Fritzing thing people use. I believe it is a freebie.

OK just make sure you are using limiting resistors. If they are not in the kit, it doesn't mean you don't need them.

Can do, but how do i know which resistors to use?

Probably correct. I'm an architect so I just use my workaday CAD and I don't know about the dedicated stuff, but it is around. There is that Fritzing thing people use. I believe it is a freebie.

Okay ill try to get that working and see if i can produce a sketch

rockstar8577: Can do, but how do i know which resistors to use?

There is plenty on WikiGoogle and the playground note has some stuff too.

rockstar8577,
I definitely “ain’t no expert” but Fritzing IMHO is a piece of crap that is hard to read and belongs in the kindergarten. In case you can’t tell I do not like it :smiley: For someone starting out (like myself) I have found Tinycad to be easy to read and easy to use

Here is what a simple circuit looks like using it, Pedro.

The resistors belong in the segment leads, not in the common lead. This means that you will need 7 (or 8 if you use the decimal point) of them.

Can do, but how do i know which resistors to use?

You could start with the ones that came in your kit.

Don

Okay so im using the 330 resistors, which i have connected between the pins of the display and jumpers connected to the arduino. Do i need resistors between the ground and the arduino? Now just some code?

Okay i have it lighting up somewhat, but it wont light up all the segments. And also how do i select each digit individually? Scratch that got all the segments lighting up, except the decimal at the bottom. Though i still don't know how to select a certain digit.

Though i still don't know how to select a certain digit.

You connect one of the cathodes (pin 6, 8, 9, or 12) to GND and the corresponding digit will turn on.

Don

floresta: You connect one of the cathodes (pin 6, 8, 9, or 12) to GND and the corresponding digit will turn on.

Don

But how to i stop it from being connected to GND?

But how to i stop it from being connected to GND?

That would depend on how you connected it to GND in the first place.

If you are using a wire in a breadboard hole you pull the wire out.

If you are using a switch you open the switch.

If you are using a transistor then you bias the transistor (drive it with the proper base signal) until it is not conducting.

If you are using a microprocessor I/O port you make the port 'high' or '1'.

Don

floresta: That would depend on how you connected it to GND in the first place.

If you are using a wire in a breadboard hole you pull the wire out.

If you are using a switch you open the switch.

If you are using a transistor then you bias the transistor (drive it with the proper base signal) until it is not conducting.

If you are using a microprocessor I/O port you make the port 'high' or '1'.

Don

Well i would like something controllable by the code. So the first way is out, along with the second. The third way i don't really know anything about. And the fourth way, how do i do that when those pins need to be grounded? As in how do i have a pin be grounded but also use an I/O port?

I think you had better start by figuring out how the 'blinky' sketch works. Then use that knowledge to get the same type of action with a single external LED. Only then will you be ready to even consider dealing with a seven segment display, much less a 4-digit multiplexed version.

Don

floresta: I think you had better start by figuring out how the 'blinky' sketch works. Then use that knowledge to get the same type of action with a single external LED. Only then will you be ready to even consider dealing with a seven segment display, much less a 4-digit multiplexed version.

Don

By 'blinky' sketch i assume you mean the blink sketch which i have already done and i already understand that. I already have my display lighting up and if it was a single digit display i would be fine and dandy. The problem i have is the 4 GND pins each control 1 digit each. Now how can i mess with the GND pins when they have to be connected to GND. I saw this tutorial which is very similar to mine here. Now if i understood that diagram correctly is it possible to have a jumper wire connected between the GND pin and the GND line?

rockstar8577: The third way i don't really know anything about.

I'm afraid this is what you do need to know about. The tutorial you allude to uses the microcontroller to do that. Your display is common cathode, like mine. The digits are selected by grounding their cathodes. In short, you don't mess with the pins, that's Arduino's job, as shown ion the bottom diagram. No ground wire needed, unless you want to make the arduino redundant.

Nick_Pyner: I'm afraid this is what you do need to know about. The tutorial you allude to uses the microcontroller to do that. Your display is common cathode, like mine. The digits are selected by grounding their cathodes. In short, you don't mess with the pins, that's Arduino's job, as shown ion the bottom diagram. No ground wire needed, unless you want to make the arduino redundant.

Yay i got it working. I thought i had to ground it but i never thought of grounding it that way.