Help Moving working project from LED 7 Seg to LCD 7 Seg

Hi All,

I successfully built a project using 7 segment LED display, it works perfect! Very happy with the function of the code with LED display - the only problem is it's not viewable outside where I plan on using it most of the time so after a ton of research it appears LCD 7 segment might be a good option, similar projects use this type of LCD display (if you have a better idea, I'd like to hear it and why it'd work well)

This project only needs to display numbers and the numbers are updated every 1 second. I think the static LCD will be perfect and it's clearly viewable even in direct sunlight, I only need 3 segments and the LCD's I currently have are Lumex 3 segment. My goal is to have nice large 3 digit numbers clearly displayed that can be read outside, the numbers will update in the code with millis() every second.

The issue I'm having transferring over my design to use a reflective static LCD - I can't seem to find any information more than an explanation on the theory of how to correctly drive an LCD since it requires reversing polarity (AC) I have some ideas on how it might work and I've seen a proof of concept using XOR for one pin, driving the com pin and flipping the other pin with an XOR, the explanation I found basically ended there and left me with no practical idea where to start, I'm looking everywhere and can't find anything on driving a static LCD with arduino so I'd appreciate any help pointing me in the right direction, I am completely stuck right now and would appreciate any help.

I would like to drive the LCD correctly so that it lasts a while or if there's a better option I'd like to know what that is.

Thank you everyone one on here!

I am not sure what LCDs that you have. Are they like the ones in this page?

Can you post a data sheet for your displays?

What Arduino board are you using?

Please read the "How to get the most of this forum" post.

I think I might have found what I need with a lucky search query - something like this: https://www.mouser.com/ProductDetail/Renesas-Intersil/ICM7211AMIPLZ?qs=9%2BF8okdJ4RNlkHomdDSbCA%3D%3D

I’m really surprised I can’t find more projects using this, if anyone knows of any that would help me a great deal to check them out. If I can get mine to work I’d like to make a tutorial on it, the reflective LCD’s are nice because they’re not that expensive, you can get them custom made and they’re very visible in sunlight, low power.

I’m also looking for any help to code this efficiently using the fewest number of pins possible on the arduino, so any links to projects, code tips or anything relevant I will appreciate very much. This is something I haven’t been that good at though, I’m sure I will want to add more buttons to a future project and need all the pins I can get open.

What do you think the best way to code the display segments through the lcd driver are while using the fewest pins?

groundFungus: I am not sure what LCDs that you have. Are they like the ones in this page?

Can you post a data sheet for your displays?

What Arduino board are you using?

Please read the "How to get the most of this forum" post.

Thanks for replying! Here's a link to the datasheet: https://www.mouser.com/datasheet/2/244/LCD-S301C31TR-1134333.pdf

I'm using the genuine uno for prototyping, and then I'll build the project in a case and use the nano so it's a decently small footprint, if I can go smaller I'd like to for the board. The original limiting factor was the battery and I've scaled that down to about the size of the nano for my last build with the LED.

If I could find a slightly larger 3 segment LCD that would also be perfect - 3 to 4 times larger would be ideal. I haven't been able to find one that size without getting it custom.

chemengineer: I'm using the genuine uno for prototyping, and then I'll build the project in a case and use the Nano so it's a decently small footprint, if I can go smaller I'd like to for the board.

Pro Mini.

I’m really surprised I can’t find more projects using this

Maybe when you have tried, you will understand :wink:

This says it needs 5V AC to operate. Maybe that’s an error, but if not, where will you get 5V AC to drive it?

Even if that should have read 5V DC, you will need 24 output pins to control the 24 segments. You cannot multiplex it like you would with an led display, which would need only 11 pins.

Would this be good?

PaulRB: This says it needs 5V AC to operate. Maybe that's an error, but if not, where will you get 5V AC to drive it?

Well of course it requires 5 V AC to drive it - it's a Liquid Crystal Display - they always require AC!

You drive the common backplane with a 5 V square wave (precise 50% duty cycle, via a flip-flop if using discrete logic), and each other pin via an EX-OR gate. :grinning:

Unlike the 1602/ 2004 displays, you don't have to worry about the contrast voltage since it is only two level drive.

PaulRB: Maybe when you have tried, you will understand ;)

|312x500

This says it needs 5V AC to operate. Maybe that's an error, but if not, where will you get 5V AC to drive it?

Even if that should have read 5V DC, you will need 24 output pins to control the 24 segments. You cannot multiplex it like you would with an led display, which would need only 11 pins.

I'm finding it more difficult than the widely used options for sure! Though it doesn't seem impossible or impractical. It does use 5V AC so basically using an LCD driver will take care of the alternating phase, this is also good because it should take up less pins than my LED display needed. I'll definitely share how to do this once I get it working and which chips and displays worked.

PaulRB: Would this be good?

|500x375

That's almost exactly what I'm looking for! The battery charge could also come in handy since I'm using a battery for this project, I will probably buy a couple of those to test out as well, the LCD's I have are really good size for the application, I think most clocks I've seen use the reflective LCD's. I have a kitchen timer that I put in a waterproof phone case to test the visibility, it worked well. In the process I did discover that the timer on my kitchen timer's timing is off by at least a few seconds in a minute!

Thanks for all the suggestions!

Here's a couple of other displays - seems like alot more coding though unless there's a library that'd be compatible. In the datasheet they show 7 segment.

-https://www.mouser.com/ProductDetail/Displaytech/64128K-COG-FA-BW?qs=zkctU4NzKYfIe1teLpQmcw%3D%3D and backlit versions of the same display: -https://www.mouser.com/new/displaytech/displaytech-rgb-backlights/

This one could be useful for some projects as well, more helpful datasheet: https://www.mouser.com/ProductDetail/ELECTRONIC-ASSEMBLY/EA-DOGM132L-5?qs=s9z6UkyjM7ragz80GpdVLQ%3D%3D

I ordered a few types of lcd drivers to try out with my lcd displays, it's actually not that complicated pin wise for the 7 segments even though there are more pins than an LED 7 segment, the challenge is powering the backplane and flipping the phase so the average voltage is 0, which the driver chips are designed to handle, so hopefully I can get something to work and share it with everyone, I'm sure I'm not the only crazy person trying to make a display useable outside in the sun.

I also like the e-paper displays, but I've read direct sunlight can affect them, otherwise those are pretty cool.

Paul__B: Well of course it requires 5 V AC to drive it - it's a Liquid Crystal Display - they always require AC!

The 16x2 and 128x64 lcd I have used don't "require" AC, in that they don't require me to provide it. They may have an internal circuit to generate it, and so might the module the OP refered to, as far as I know, I'm not familliar with them.

128x64 glcd displays with st7920 chip might be worth looking into. Avoid those with ks0108 chips, they require a lot of pins. There are several libraries available which will draw digits in a large font, such as the “u8g2” library.

Here’s a circuit I built once like that:

PaulRB: The 16x2 and 128x64 lcd I have used don't "require" AC, in that they don't require me to provide it. They may have an internal circuit to generate it, and so might the module the OP referred to, as far as I know, I'm not familiar with them.

You actually quoted the specification and the pinout from the LCD datasheet citing the "COM" backplane. There are no "power" connections; it is the bare Liquid Crystal display itself, it cannot "generate" anything.

The Hobby-Components display on the other hand is a complete module with six connections. It is a (multiplexed in this case) 16 pin LCD mounted on a PCB with a COB chip (HT1621) which clearly does generate the "common"s and segment voltages. Incidentally, it appears to be a 5-digit plus annunciator version rather than the much cheaper 6-digit version.

Hi,

This post is interesting to me, because we have been working on something new and interesting. We are making a few displays that emulate 7-segment displays.

Here is a 3.9" TFT, driver by I2C from an Arduino.

7-Segment font and a Neon Red font

example of the command structure

Sending numbers
“@ F16 0 3.14 #”
F16 = Field command 16 - update data value
0 = field 0
3.14 = new value

Colour of Numbers
“@ F21 0 255 0 0 #” 0 = field 0, RED Colour, RGB 255 255 255

Backlight Brightness
“@ C201 255 #” 0-255 brightness

Quick video

NB3.mpg (1.71 MB)

It's taken a few complete failures and alot of wiring but I've almost got it working perfectly, my last challenge is getting the semicolon to display, and adding my button functions back in, the display looks really good and it's going to be perfect for my application.

I was able to almost get it to work with a Ti 4055 chip - it would take 3 to do what I'm doing, it sort of worked the way I wanted with the 3 chips but then I decided to do it better using a single chip so Microchip AY0438 is the lcd driver I'm using, it's definitely doable if you have a little, alot of patience lol. You can also daisy chain the AY0438 if you have a ton of pins, I'm using a 4 digit 7 segment LCD.

This is a great option for anyone who wants low power LCD's for their project, I'm going to use a 3.3V rechargeable battery to power it.

Thanks everyone for your input :D

I was able to build my project and after playing on breadboards for months and making ALOT of mistakes. The first couple of things I tried didn't work or had bugs. I spent a great deal of time being soo close and it seemed impossible at times, I'd have something working then try to prototype it and it'd fail.

In the end I'm really happy with what I came up with, it works great and I'm sure it will last a long time 8) :D 8) :grinning:

I ended up going with the arduino pro mini as suggested and that's minified my project

The size is perfect, the board is about the size of the LCD, the pro mini is also easy to program compared with what I started with, and economical.

I'm planning on making some videos to share all this with anyone who's interested

also planning on making some pcb's with LCD controller and screen so it's easy to hook up any arduino with 4 wires to the pcb for prototyping, if anyone is interested in one feel free to contact me and I'll put some together. Takes the guess work out of wiring and I had some problems getting a good connection on my breadboard with the chip and lcd since there are quite a few pins

Hopefully that will save you some time if you're looking to build a project with and LCD,

there really are alot of benefits to using reflective LCD's - pretty low power consumption, viewable in sunlight which is a must for my project, widely available and inexpensive compared to alternatives, lasts along time as long as it's driven with a lcd driver chip.