HowTo: Build a retro-smart home display via analog displays

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The other day I found an old control panel with old analogue displays when mucking out the cellar. It came to me the idea that somehow it must be possible to display data of my SmartHome on it.

Just to have the current climate data such as temperature, humidity, etc. displayed, these displays should be pretty good.

How to do it and what you have to consider is described in the following article.

Hints for our lovely english readers: Basically, many of the articles on Nerdiy.de are translations from the original german articles. Therefore, it may happen here and there that some illustrations are not available in english and that some translations are weird/strange/full of mistakes or generally totaly wrong. So if you find some obvious (or also not obvious) mistakes don't hesitate to leave us a hint about that in the comment section. 
Also please don't get confused, that instead of a "dot" often a "comma" is used as decimal separator. 🙂

Safety instructions

I know the following hints are always a bit annoying and seem unnecessary. But unfortunately, many people who knew it "better" from carelessness lost their eyes, fingers or other things or hurt themselves. In comparison, a loss of data is almost not worth mentioning, but even these can be really annoying. Therefore, please take five minutes to read the safety instructions. Even the coolest project is worth no injury or other annoyance. https://www.nerdiy.de/en/sicherheitshinweise/

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Requirements

Helpful Articles:
Before you start with this article you should have dealt with the basics of soldering. Information on this can be found in the following article.
Electronics – My friend the soldering iron

Required material:

In the following list you will find all the parts you need to implement this article.

Required tools:

In the following list you will find all the tools you need to implement this article.

Collect required parts

In the following picture you can see the parts you need to build your own Retro-SmartHome-Display.

Print the required 3D parts

Download all required STL files: Build your own retro-smarthome display via analogue displays

You can also find modular housing templates in the More than Two Displays section of an enclosure.

Housing for a display:

Ihr könnt die 3D-Ansicht der STL-Datei mit gedrückter Maustaste rotieren. Rein- und Raus-Zoomen könnt Ihr mit dem Mausrad.

Housing for two displays:

Ihr könnt die 3D-Ansicht der STL-Datei mit gedrückter Maustaste rotieren. Rein- und Raus-Zoomen könnt Ihr mit dem Mausrad.

Attach the alternate display scale label

In this step, the alternative labels of the display scales are glued to the display. Because you don’t want to display voltages with the analog displays but other values such as temperatures, humidity, etc. For this, the scales have to be adjusted slightly.

In the following pdf file you will find templates for temperature (inside and outside), humidity (inside and outside), air pressure, hour and minute in German and English. Simply print them out and stick them on the scales of the analogue displays as described below. This is best suited for printable label paper, since this is already provided on one side with an adhesive layer. If you would like to have them in other languages too, just ask for it in the comment section. 🙂

Download: scale-lettering.pdf

Loosen the screws in the front cover …
… and take everything apart until you can see the thin scale plate. Be careful not to bend or otherwise damage the sensitive pointer.
If you have cut out the alternative display scale label of your choice, you can stick it on the previously removed scale plate. Here you should work very clean, because you can (and should) see this scale plate and the alternative display scale label later very good.
If you have pasted the alternative display scale label on the scale plate this should look something like this.
The pasted scale plate you can now insert again into the analogue displays and build them together.

Attach backlight

So that you can illuminate the displays later in the dark, an LED backlight is installed.

To do this, you must first remove any existing obstacles. You have to get to the back of the scale surface.
There you drill a small hole with a diameter of about 3mm in the middle. When drilling, make sure that you do not damage the scale plate on the front when piercing.
The small hole can then be drilled with a 6mm to the final desired size.
Now you can put one of the ready-bought or lead-prepared WS2812 LED’s …
… glue into the drilled hole as shown.
That’s it with the installation of the backlight. Build the display parts back together …
And install them in the housing.
For this, the display is pushed from the front into the housing opening. Then you can fix the display on the inside with nuts.
You repeat this with the second display, in which of course you have already pasted the new scale label.
Then you can also attach the backlight to the second display.
Removes any obstacles …
… and drills again a sufficiently large hole as in the previous display.
There you stick now the remaining WS2812-LED …
… and reassemble the display.

Prepare connecting cables

Of course, in order to be able to control the pointer angle of the analogue displays later, they must of course be connected to a voltage source. For this purpose, the connecting cables are prepared in this step.

Cut off four pieces of wire about 10 cm long and strip the ends for about two cm.
Tin the ends of the wires …
… and turns the tinned ends into rings. This is best done with round nose pliers. The diameter should be at least four mm.
The other end of the lines then you have to strip about five mm and tin.
The two blue wires can still be connected. They are connected to the “negative pole” of the analog display.
The “negative pole” can be recognized by the “minus” next to the connection screw of this analog display. To connect the wire there, you first put a washer …
… then the previously bent wire …
… then a washer again ….
… and a spring washer over the connection screw.
This whole “package” can then be fixed with a nut.
These should attract you “Hand fixed”. Consider here: After “fixed” comes “off”. 🙂
Repeat this for the other “minus pole”.
You can then connect the remaining “positive poles” of the analogue displays with the other lines.
The connected lines must now be connected to the PCA9685 breakout board.
To do this, you first tin the contact “GND” (in the photo on the upper left corner of the PCA9685 breakout board) and the top contacts of the connection rows “1” and “2” (in the photo bottom left).
In this context you can also tin the contacts “GND”, “SCL”, SDA “,” VCC “and” V + “on the opposite side of the PCA9685-Breakout-Board.
Then you can connect the leads to the PCA9685 breakout board as shown. The (common) “minus pole” (here the blue line) is connected to the contact “GND” of the PCA9685 breakout board. The “plus poles” of the analogue displays are connected to the prepared contacts of “1” and “2”.
The connected PCA9685 breakout board should look (so far) something like this.
For the PCA9685 breakout board to work it must now be connected to the power supply – as well as the WS2812 LED’s. For this purpose, a common supply line for LEDs and PCA9685 breakout board is now being prepared. To do this, separate the individual cables of the supply line of the WS2812 LEDs by approx. ten mm.
In addition, you prepare two lines on which you strip one end each ten mm and the other end each five mm.
The ten mm stripped ends you twist now – as shown – with the wires of the WS2812 LED’s and tin them with some solder. You should already pay attention to which wire of the WS2812 LED’s is the “5V” wire. In this case, it is the wire connected to the red line.
This should look something like this.
Now you solder the “5V” line to the contact “VCC” of the PCA9685-Breakout-Board …
Closeup of the soldered wire on the PCA9685 breakout board.
The other line of the supply line is then soldered to the contact “GND” on the PCA9685 breakout board.

Connect the ESP8266 adapter board

The now prepared lines must of course still be connected to the “heart” – the ESP8266 adapter board.

First of all, the contacts must be prepared.
Tin the contacts “5V”, “G”, “D4”, “D2”, “D1” and “3V3” – as seen in the picture.
Then you can connect the “plus” line (in the photo the red and red/transparent line) and the contact “5V” of the ESP8266 adapter board.
Repeat this with the “minus” line (in the photo the blue and transparent line). Connect them to the contact “GND” of the ESP8266 adapter board.
To fully connect the WS2812 LED’s, you must now connect the data line (the last remaining one coming from the WS2812 LED’s) to contact “D4”.
Prepare now another five to ten cm long wires by stripping and tinning the ends of the wires about 5mm.
The first of these three wires is to power the PCA9685 breakout board at 3.3V from the ESP8266 adapter board.
Solder the cable to the contact “VCC” of the PCA9685-Breakout-Board …
… and the other end to the contact “3.3V of the ESP8266 adapter board.
The next wire to be attached connects the “SCL” bus line between the PCA9685 breakout board and the ESP8266 adapter board.
Solder the wire to the contact “SCL” of the PCA9685-Breakout-Board …
… and the other end to the contact “D1” of the ESP8266 adapter board.
The last wire (then you are done with the soldering work) connects the bus line “SDA” between PCA9685 breakout board and ESP8266 adapter board.
Solder the lead to the contact “SDA” of the PCA9685 breakout board and the other end to the contact “D2 of the ESP8266 adapter board.
That’s it with the soldering work. 🙂 Your setup should now look something like this.
Now you can “stow” the electronics a bit.
Stick the PCA9685 breakout board with some hot glue in the middle as shown between the analog displays …
… and the ESP8266 adapter board as shown next to it. Note that the USB port on the ESP8266 adapter board must remain accessible because it needs to be programmed and powered.
That’s it with the assembly of the required hardware. 🙂

Other variants

The great thing about the PCA9685 breakout board is that it offers up to 16 outputs. That means you can connect up to 16 displays.

To produce a housing for one or two analogue displays, a 3D printer is enough. Unfortunately, most 3D printers are too small for more than two displays. One way you can still combine multiple ads is described in the section More than two displays in one enclosure below.

Housing version with only one analog display.
If you want to use more than two ads, you can also make a wooden case.

More than two displays in one housing

… are difficult to implement in the way described above. At the very least, a case with room for more than two displays is very difficult to print using a 3D printer. Most 3D printers simply do not have enough space on their print bed.

At least if you want to print the case in one part, this will not work. In case you have no problem with screwing the case out of several parts, here is a suggestion how to do it all the same. Unfortunately, there are currently no pictures with a step-by-step guide. I will insert these as soon as possible.

However, the assembly can be very well guessed on the basis of the 3D templates. For those who still want to try it out:

A few pictures explaining the assembly, you will find the view of the required 3D files.

Download the required STL files: Retro-SmartHome display modular housing

Middle part of the modular housing:

Ihr könnt die 3D-Ansicht der STL-Datei mit gedrückter Maustaste rotieren. Rein- und Raus-Zoomen könnt Ihr mit dem Mausrad.

End part of the modular housing:

Ihr könnt die 3D-Ansicht der STL-Datei mit gedrückter Maustaste rotieren. Rein- und Raus-Zoomen könnt Ihr mit dem Mausrad.

To assemble a housing with, for example, two elements, you need 12x screws (for example, M4x16) and 12 nuts. For each additional element, four are added.
The housing parts are then simply screwed together.
In this way, theoretically, an infinite number of analogue displays can be accommodated in one housing.
Detailed view.
Detailed view.
Detailed view.
Detail view of the front including analogue displays.
Of course, the gap dimensions and quality of the case also depend on the print quality of your 3D printer.
Detail view of the complete housing.

Flashing firmware

Now it is time to transfer the firmware to the display.

Program the ESPEasy firmware including the “Nerdiys PanelMeter” plugin to the ESP9266 adapter board. How to do this is explained in the following article: ESPEasy – Install and configure the NerdiysPanelMeter plugin

I hope everything worked as described. If not or you have any other questions or suggestions, please let me know in the comments. Also, ideas for new projects are always welcome. 🙂

Fab

P.S. Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you appreciate it that I share these information with you, I would be happy about a small donation to the coffee box. 🙂

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