Segment displays

[Mach7]

Hello ame,

Thank you for the information, it is very helpful in navigating a choice.

What do you think of this...I would like to use the 4031BG coupled with the HTK16K33 led control drive unit.

https://www.aliexpress.com/item/32717990061.html

My soldering skills are quite good...so I was thinking I could solder individual wires to the LED pins leading back to the driver unit...what are your thoughts on this?

This way it solves my lateral space problem on the CDU head.

Jim

[ame]

Yes, that would be fine. The HT16K33 is a common cathode driver, so make sure you get the right display.

It's also my current favourite display chip, and has the capability for switch input as well as LED output. I'd recommend connecting the switches to the Arduino to start with however.

Here's an example of using the HT16K33 to drive a 4-digit 7-segment display:
https://protosupplies.com/product/ht16k33-led-controller-module/

You will wire yours up in a similar fashion, except you will use only C0 C1 and C3. I'm not sure why the example does not use C2. It is explained in the text, but I don't understand the reasoning. It's for the colon in a clock display, so maybe it's hard-coded in the library. I would prefer to use C0 C1 and C2, but we can figure that out later.

Basically you hook up your display to the HT16K33 board with 11 wires (8 segments, 3 digits) then you hook up the HT16K33 board to the Arduino with 4 wires (5V, GND, SCL, and SDA). SCL is A5 on the Arduino, and SDA is A4. Your display is done!

[ame]

There's also this:
https://m.aliexpress.com/item/33049299832.html

It's a clone of the Adafruit LED backpack, based on ht16k33.

This time the leads are spaced too wide, but again I think the 3-digit module could be persuaded to fit.

It might be an option if you have space for the PCB just behind the displays.

[Mach7]

I just noticed that the  4031BG model LED display is yellow/green....not my preference as I am looking for yellow.

I did not realize how hard it is to find a 3 digit, 7 segment, yellow common cathode LED display in my size range.

Maybe all out of stock due to COVID..can't transport from China(?)

My search continues.....

[ame]

Is 0.36" acceptable?

[Mach7]

Yes for sure...do you have a link?

BTW is there a reason for the lack of 3 digit displays? I am even looking on eBay now.

[ame]

I searched on AliExpress with "display segment yellow 0.36" and got a few hits. Remember to choose common anode or cathode to match the driver, and double check the colour. Price, batch quantity, and shipping seems to vary a lot.

You could hand-wire the display to a driver as discussed, or find an existing module and remove and replace the display. As, er, also discussed.

You could also buy any module for the purpose of development, and replace it with something "better" later.

[ame]

I don't know why 3-digit displays are uncommon. I think it's more a case of 4-digit being extremely common (for clocks, I expect).

And once you start getting very specific about your requirements the chances that that particular combination is common become vanishingly small.

[Mach7]

So....i have found a suitable LED display solution...it is the CL3631BH
which comes in bright yellow
...a bit smaller, but will do perfectly for my application...the only problem is that it is a common anode type so my search now turns to a compatible LED driver....any thoughts or links?

Having a hard time finding a common anode driver now:(

On the bright side...im getting close to ordering some bits and pieces!

[ame]

Just for completeness I am reviewing the driver list I made earlier:

TM1637  Common Anode, 8 segments x 6
MAX7219 Common Cathode, 8 segments x 8
HT16K33 Common Cathode, 16 segments x 8

I am ignoring the 74HC595 as it is a single chip per digit, not a matrix driver.

So, you have found 0.36" 3-digit yellow common anode.

It will work with the TM1637.

Here is another common anode:
https://www.aliexpress.com/item/32804978824.html

This is indeed labelled CL3631BH, but often the photos don't match the specific component.

That 3-digit CA display is also found on the 6-digit board from Robotdyn:
https://www.aliexpress.com/item/32798344970.html

There are two of them, to make 6 digits. The TM1637 will drive a maximum of 6 digits.


If you wanted to use the MAX7219 or HT16K33 you would need common cathode. Like this guy:
https://www.aliexpress.com/item/32642714446.html


Frankly, it's really hard to stay focused. Even though I know what I am looking for I have to keep double-checking what I am looking at.

[ame]

As I said, I am a fan of HT16K33, but, I happened to have some TM1637 modules in my junk box. The 4-digit display is red. The 6-digit display is yellow:



I desoldered the 4-digit display, and one of the 3-digit displays:


Then moved the 3-digit display to what was the 4-digit board:


Not tested yet, but it ought to work. You can imagine soldering 11 small wires from the display to the board if you didn't want to have the board right behind the display.

[Mach7]

I know what you mean....i have about 25 windows open for various parts etc...and my head is beginning to swim....

Having said that, I think I have found a compatible solution after reviewing your last two posts..

I am looking at the LED display 3631BH which is a common cathode 3 digit 7 segment display.

https://www.aliexpress.com/item/32642714446.html

The driver will be the TM1637 Red Digital Tube LED Display Module & Clock LED

https://www.aliexpress.com/item/32948103200.html?spm=a2g0o.cart.0.0.47213c00qpG5wp&mp=1

Before I order these units...i do have a question...first...I cannot find anywhere in the specifications that tells me that this unit is a common cathode type..

and second, i am a bit concerned with the text in the explanation of the driver that says "red digtal tube display".

I am assuming that since the LED is yellow, the driver should not have an impact on the emitting color (?).

so...have I picked the right combination of display and driver...or am I back to square 1 in my continued search.

Thanks ame

Jim

[ame]

Well, that worked. It's hard to capture the colour properly, but it looks fine on the bench. I set the driver brightness to 3. The range is 0 (off) to 8 (full). I'd recommend you put a piece of smoked acrylic over the front as a display filter. It will make it look much nicer, and boost the contrast a bit.

The Nano is plugged in to a base PCB with screw terminals. Easy to find, and cheap, but it adds bulk. You probably want one, or a breadboard for development, but not for the final assembly.

[ame]

I know what you mean....i have about 25 windows open for various parts etc...and my head is beginning to swim....

Having said that, I think I have found a compatible solution after reviewing your last two posts..

I am looking at the LED display 3631BH which is a common cathode 3 digit 7 segment display.

https://www.aliexpress.com/item/32642714446.html

The driver will be the TM1637 Red Digital Tube LED Display Module & Clock LED

https://www.aliexpress.com/item/32948103200.html?spm=a2g0o.cart.0.0.47213c00qpG5wp&mp=1

Before I order these units...i do have a question...first...I cannot find anywhere in the specifications that tells me that this unit is a common cathode type..

and second, i am a bit concerned with the text in the explanation of the driver that says "red digtal tube display".

I am assuming that since the LED is yellow, the driver should not have an impact on the emitting color (?).

so...have I picked the right combination of display and driver...or am I back to square 1 in my continued search.

Thanks ame

Jim

Back to square one I'm afraid. TM1637 is common anode...

If you want to know why, read the data sheet:
https://www.mcielectronics.cl/website_MCI/static/documents/Datasheet_TM1637.pdf

Also, don't worry about digital tubes. I don't know for sure, but I think it is a confusion with, or mis-application of, "Nixie tubes".

And indeed, the driver does not affect the colour. The colour is set by the LEDs in the display. The driver just turns them on and off.

[Mach7]

oK...Actually no problem, I will stick with the same driver and revert back to the original 3 digit yellow display;

https://www.aliexpress.com/item/32804978824.html?spm=a2g0o.cart.0.0.2a003c00cMffwI&mp=1

This display is denoted as an anode, so this combination of driver TM1637 and this change in LED should work....(?)

[ame]

Reckon so.

You'll have to desolder the red 4-digit display from the board then solder the yellow 3-digit display in place (or attach it with 11 wires).

Then you will have exactly what I just made, which I (now) know works.

In the meantime, if you can get hold of an Arduino (Uno or Nano) we can play with the thumbwheels.

[Mach7]

Ok...like I said...i will have a lot of questions.

Here is my Arduino question...

When I go to the Arduino website, the nano is listed at 20 dollars and change...when I go to Aliexpress, they have the nano's on for a couple of bucks.

The price is not a concern for me...but I notice that the arduino models on Aliexpress do not use the word "Arduino" which makes me think they are a knock off of the original ??

If so...would you suggest buying the original equipment, or would a copy of a nano work sufficiently?

thanks ame

Jim

[ame]

Ah.

Well.

It's like this. The Arduino design is Open Hardware and can be legitimately copied and sold by anyone. Fundamentally it's a $2 Atmel ATmega328 microcontroller on a PCB and there's not much to it. However, only official Arduinos can carry the Arduino name, and if you do buy an authentic Arduino then you are supporting the development of the hardware and the software that comprises the Arduino ecosystem and makes it so easy to use. You'll also have aftersales support, a warranty, and all that good stuff.

You can get it straight from the horse's mouth here:
https://blog.arduino.cc/2013/07/10/send-in-the-clones/

If you buy an "official Arduino" for $5, it's probably fake and illegally using the name and logo. If you buy an "official Arduino" for $20 from some guy in a van, it's probably fake, and you've been robbed. If you buy an "official Arduino" for $20 from a legitimate store, good for you! You're helping everyone. If you buy a "Nano microcontroller board" from somewhere cheaply it probably does not say Arduino on it, so it's a clone, and it's probably ok. You've saved some money, but you are educating yourself, which is the whole point. The next person you excitedly tell all about Arduino might altruistically buy an official part. Or maybe you will later.

I generally buy clones from AliExpress. I've never had a dud, but they are out there. Once you've started getting into it then you're going to need more than one...

[ame]

Ok. I've hacked together some code. I decided to connect the thumbwheels in a matrix fashion so that there will be enough pins for TGT later.

I have a dimming potentiometer, which you can include if you like. It activates the 8-step dimming function of the TM1637.

I have implemented the TEST button, and the MCT button. Everything can be changed, of course.

I have code to read the thumbwheels, but I don't have any to test. I can also calculate N1 from Tref. Everything should work (when it's finished), and I can't see any reason why you can't build something that works in the way you described.

Once you have an Arduino you can hook up a thumbwheel and test it. Arduino has a serial I/O port which can be used to print out the state of the internal program. So you could change the thumbwheel and see the results printed on your PC screen.

I suggest you buy several of any of the cheap parts you are using (including Arduinos, following on from the previous message). It will allow you to keep going if you want to build something new, or another copy of what you have or replace any parts that become inexplicably inoperative.

[Mach7]

That all looks and sounds great...i can hardly wait to see this think in action!!

So here is where I stand..

I have ordered all the parts off Aliexpress, plus a number of other bits and pieces such as different size displays, connection leads, etc etc so I have enough parts to become flexible with the project.

I have also ordered a handful of nano, and UNO boards, plus the (bulky) connection board you referred to in one of your last post along with compatible usb connection cables.

So know we will have to wait for the parts to start trickling in!

-Jim

[Mach7]

Hello Andrew,

Just a quick question...

I am mapping out the pushbutton switch outputs for the takeoff button.

Is Arduino capable of outputing illuminating a single green LED on the switch once the button is pressed to activate the thumbwheel/led segment display information?

[ame]

Somehow I just knew you were going to ask something like that...

The short answer is yes.

But I'm running out of pins.

There are solutions to "running out of pins", because it happens all the time.


A Nano has
14 digital only pins
6 analog/digital pins
2 analog only pins

Two of the digital pins are used for serial communication, and one is attached to a built-in LED, which leaves 11 digital only pins.

So far, I have allocated 4 pins for thumbwheel bits, and one for each thumbwheel. There will be 6 thumbwheels, so 10 pins are required.

The LED module requires 2 digital I/Os.

The switches, TO, MCT, TGT, and TEST need one each, so that's another 4.

Total is 16, and we have 11+6=17 digital I/Os available. Leaving one for the LED. Hooray.

The brightness pot is hooked up to one of the analog-only inputs.

We could connect the switches to the thumbwheel bit inputs, then we'd only need one more pin for four switches instead of four pins, which would release three pins, leaving four free.

I know I said originally we could afford to waste pins. Now we can't, but there are solutions if we need them.

[Mach7]

Ok thanks Andrew,

If I did need an LED lamp output, it would only be for the Takeoff button to illuminate a single chevron when pressed in, and at that I might not need it at all.

Just looking at my initial CDU construct and trying to use some existing inputs and outputs.

Jim

[ame]

No worries. As I said, there is currently one pin left, which you could easily connect to a single LED. You need a resistor inline with the LED, then connect it from the pin to ground, or from 5V to the pin.

I've been working on a CDU too. Originally for a Bombardier Challenger 300.

[Mach7]

Cool, I currently fly the CRJ900.