# LED digital road sign can you give me with first steps?

#### Mellisa_K

Joined Apr 2, 2017
359

Firstly I want to acknowledge and thank these kind AAC members who have helped me in the past (I know I’ve missed several, sorry):

My project aim:
Build a programmable monochrome digital LED road sign about 2.5m wide by 2m high

Example outcome
Could you please have a look a the two pics attached, showing an example of a digital road sign that I want to build.

Background
My uncle just opened an Indian takeaway in what I think is a poor retail site. I offered to build him a road sign to improve his exposure to passing traffic and to bring in more customers.

The project in totality consists of three separate tasks (I need help with #3 below pls):

1 Road trailer and built in steel structure (later: not within the scope of this current project)

2 Solar powered battery rig (later: not within the scope of this current project)

3 The LED panels and associated electronics and software (this is what I want to build now; I believe I am capable. I have all the equipment and I can follow circuit diagrams and solder single sided circuit boards. I have some experience with Arduino).

Questions for AAC members
Can anybody help me by pointing me in the right direction so I can learn about how these signs work and what components I need to search for?

I need for example to:
1 Find a circuit diagram
2 Identify the components
3 Work out how the programming works and what options I have for this part of the project.

#### jpanhalt

Joined Jan 18, 2008
8,318
1) The printing to screen is almost certainly done with a microcontroller or small computer. Assume a microcontroller.
2) Consider it like a graphical LCD display (GLCD) as you will probably need your own font table. Maybe the screen to which you are putting data has a built in controller and fonts. You need to find that information. Assume it is simply a GLCD-like screen.
3) Find a font you like or write your own. There is a huge resource on the Internet of fonts. Here is just one: https://www.fontspace.com/category/dot matrix
4) Learn or get help coding the MCU to export the fonts. Will the interface be parallel or serial? If serial, the common type for this are SPI, I2C, and "1-wire" (RS232 type). I suggest 1-wire or SPI.
5) Those are high intensity LED's. You will need a driver. I con't help you there. But there are plenty of resources on the Internet.

#### MrChips

Joined Oct 2, 2009
19,729
If you are going to go to the trouble of building that, then think ahead and go with colour RGB LEDs.
Build it with smaller modular panels so that it will be easier to repair when one LED goes bad.
For example, each panel can be 8 x 8 LEDs.
3 x 6 panels will give you a pixel display of 24 x 48 pixels.

Assuming you want a static display only, then each panel is addressable using an RS-485 interface. All you need is to send 24 bytes encapsulated into a data packet from the main controller.

You could have simple changing display such as flashing, scrolling, or changing colours. Video graphics would be too slow. You could do GIF style animation.

For solar power, you need to calculate total average power consumption in order to size the solar panel. You will need storage batteries for night time display.

#### jpanhalt

Joined Jan 18, 2008
8,318
I suspect you will also need an RF link to a central office to change the sign without having to be onsite.

#### Yaakov

Joined Jan 27, 2019
1,610
Do you have a budget in mind? This is going to be an expensive project no matter how you go about it.

#### AlbertHall

Joined Jun 4, 2014
8,762
Maybe, depending on your locale, you should check the regulations. There may be restrictions on location, size, etc. It would be very bad to have designed and built it only to discover that you are not allowed to use it.

#### WBahn

Joined Mar 31, 2012
24,970
Yaakov and AlbertHall stole my thunder on this one.

The first thing to do is get your Uncle to establish a budget for the entire thing. Then spend a bit of time finding out what commercially made ones cost on the used market. You can probably find something for a fraction of the cost of a new unit.

Then estimate the costs for each of the three pieces you've identified. If you are anywhere close to the budget, proceed. Otherwise, you are wasting your time and your uncle's money. And keep in mind that if a new commercial unit is 10x or more the price of your budget, that there may be a reason for that and that it might be a fool's errand thinking that you can make one (that will work and not be a maintenance nightmare) for a fraction of the cost that the pros can do it.

Also, check to make sure that you can put a homebuilt electronic sign in the place you are thinking.

There are lots and lots and lots of signage options available these days. Full-color LED matrix signs of the size you are talking about seem to be in the $3000 range (new). The unit you picture has 51 columns and 28 rows (as best I can tell). That's 1,428 lights. If each light (including the display element, it's mount, and it's driver) comes in at just$2, you are right in the $3000 price range just for the parts for the display. You haven't even started talking about the programmable controller, the power supply, or anything else. Don't get lulled into the notion that you can always built it for less than you can buy it. Thread Starter #### Mellisa_K Joined Apr 2, 2017 359 Yaakov and AlbertHall stole my thunder on this one. The first thing to do is get your Uncle to establish a budget for the entire thing. Then spend a bit of time finding out what commercially made ones cost on the used market. You can probably find something for a fraction of the cost of a new unit. Then estimate the costs for each of the three pieces you've identified. If you are anywhere close to the budget, proceed. Otherwise, you are wasting your time and your uncle's money. And keep in mind that if a new commercial unit is 10x or more the price of your budget, that there may be a reason for that and that it might be a fool's errand thinking that you can make one (that will work and not be a maintenance nightmare) for a fraction of the cost that the pros can do it. Also, check to make sure that you can put a homebuilt electronic sign in the place you are thinking. There are lots and lots and lots of signage options available these days. Full-color LED matrix signs of the size you are talking about seem to be in the$3000 range (new).

The unit you picture has 51 columns and 28 rows (as best I can tell). That's 1,428 lights. If each light (including the display element, it's mount, and it's driver) comes in at just $2, you are right in the$3000 price range just for the parts for the display. You haven't even started talking about the programmable controller, the power supply, or anything else.

Don't get lulled into the notion that you can always built it for less than you can buy it.

#### Mellisa_K

Joined Apr 2, 2017
359
This is such a useful response wbahn. I do have tendency to assume I can do anything myself more cheaply. It's good to be reminded of that folly. I never thought there'd be a market for second hand ones. So thankyou for yr help

#### Mellisa_K

Joined Apr 2, 2017
359
If you are going to go to the trouble of building that, then think ahead and go with colour RGB LEDs.
Build it with smaller modular panels so that it will be easier to repair when one LED goes bad.
For example, each panel can be 8 x 8 LEDs.
3 x 6 panels will give you a pixel display of 24 x 48 pixels.

Assuming you want a static display only, then each panel is addressable using an RS-485 interface. All you need is to send 24 bytes encapsulated into a data packet from the main controller.

You could have simple changing display such as flashing, scrolling, or changing colours. Video graphics would be too slow. You could do GIF style animation.

For solar power, you need to calculate total average power consumption in order to size the solar panel. You will need storage batteries for night time display.
Great response thankyou Mr Chips. Yr lesson is incredibly useful because it tells me to think ahead. I just assumed monochrome cheaper so go with that. Also you've given me ideas to go small first. And good leads to find out more. Thanks again

#### Mellisa_K

Joined Apr 2, 2017
359
Maybe, depending on your locale, you should check the regulations. There may be restrictions on location, size, etc. It would be very bad to have designed and built it only to discover that you are not allowed to use it.
Yes this is a basic point Isnt it Albert H. I will check this. Thankyou

#### Mellisa_K

Joined Apr 2, 2017
359
Do you have a budget in mind? This is going to be an expensive project no matter how you go about it.
No budget yet. All replies so far are consistent with your point about the high cost. Thanks for the heads up
Yes this is a basic point Isnt it Albert H. I will check this. Thankyou
1) The printing to screen is almost certainly done with a microcontroller or small computer. Assume a microcontroller.
2) Consider it like a graphical LCD display (GLCD) as you will probably need your own font table. Maybe the screen to which you are putting data has a built in controller and fonts. You need to find that information. Assume it is simply a GLCD-like screen.
3) Find a font you like or write your own. There is a huge resource on the Internet of fonts. Here is just one: https://www.fontspace.com/category/dot matrix
4) Learn or get help coding the MCU to export the fonts. Will the interface be parallel or serial? If serial, the common type for this are SPI, I2C, and "1-wire" (RS232 type). I suggest 1-wire or SPI.
5) Those are high intensity LED's. You will need a driver. I con't help you there. But there are plenty of resources on the Internet.
Hello jpanhalt, thankyou for your considered reply. I'll check the technical issues you mention. It's very useful to me.

#### WBahn

Joined Mar 31, 2012
24,970
This is such a useful response wbahn. I do have tendency to assume I can do anything myself more cheaply. It's good to be reminded of that folly. I never thought there'd be a market for second hand ones. So thankyou for yr help
That is a folly that most natural-born engineer types share -- it's part of our personality that led us to be engineers in the first place. It's also something that continues to bite many of us long after we've learned that we suffer from it.

Joined Feb 20, 2016
3,154
I agree with the comments that this will be a very expensive project. Do try to look at second hand units. If you are feeling confident enough, see if you can find one that is faulty and fix it. But that could be harder that you think. Another thing, a second hand unit will probably need new batteries so take that into account as an extra expense.
After looking into all that, a new one may be the best way to go. Try to get circuit diagrams and as much info as you can so you can maintain it after the warranty has expired.

#### Mellisa_K

Joined Apr 2, 2017
359
That is a folly that most natural-born engineer types share -- it's part of our personality that led us to be engineers in the first place. It's also something that continues to bite many of us long after we've learned that we suffer from it.
Yes I get that. And it's hard to beat modern mass production. So there's maybe more to it than economics. I know I get huge satisfaction and a sense of self efficacy building anything regardless of how much I spend. Throwing money down the drain is the price we pay for learning?

#### Mellisa_K

Joined Apr 2, 2017
359
I agree with the comments that this will be a very expensive project. Do try to look at second hand units. If you are feeling confident enough, see if you can find one that is faulty and fix it. But that could be harder that you think. Another thing, a second hand unit will probably need new batteries so take that into account as an extra expense.
After looking into all that, a new one may be the best way to go. Try to get circuit diagrams and as much info as you can so you can maintain it after the warranty has expired.
Thanks Dendad. As usual yours are very useful commentsl; ike all the others. I should scale down my immediate ambition here. Baby steps I think.

#### Mellisa_K

Joined Apr 2, 2017
359
Hello all,

I've taken on board the overwhelming message from all your responses:

"Softly softly catch yee monkey"

and

"Baby steps"

How does this sound as a project, after first telling my uncle it's off until I do some R and D using a single 8×8 panel with a view to perfecting all the technologies and establishing the feasibility of scaling it up.

I'm quoting Mr Chips:

"Build it with smaller modular panels so that it will be easier to repair when one LED goes bad.
For example, each panel can be 8 x 8 LEDs.
3 x 6 panels will give you a pixel display of 24 x 48 pixels."

Any comments on that idea, friends?