While cleaning out the cellar the other day, I found an old control panel with old analog displays. This gave me the idea that it must be possible to use these displays somehow to display data from the SmartHome.
These displays should be particularly useful for displaying current climate data such as temperature, humidity, etc.
How to do this and what you need to bear in mind is described in the following article.
Safety instructions
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Requirements
Helpful articles: Before you start with this article, you should have dealt with the basics of soldering. You can find information about this 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 tool:
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.
In the section More than two displays in one housing you will also find templates for modular housing parts.
Housing for a display:
You can rotate the 3D view of the STL file by holding down the mouse button. You can zoom in and out with the mouse wheel.
Housing for two displays:
You can rotate the 3D view of the STL file by holding down the mouse button. You can zoom in and out with the mouse wheel.
Attaching the alternative display scale labeling
In this step, the alternative labels for the display scales are glued on. After all, you don't want to use the analog displays to show voltages but other values such as temperatures, humidity, etc.. To do this, the scales need to be adapted 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 these out and stick them on the scales of the analog displays as described below. Printable label paper is best suited for this, as it already has an adhesive layer on one side.
To do this, loosen the screws in the front cover......and take everything apart until you can remove the thin scale plate. Be careful not to bend or otherwise damage the sensitive pointer.Once you have cut out the alternative display scale lettering of your choice, you can glue it onto the previously removed scale plate. You should work very cleanly here, as this scale plate and the alternative display scale lettering can (and should) be clearly visible later.Once you have glued the alternative display scale lettering onto the scale plate, it should look something like this.You can now insert the glued scale plate back into the analog displays and assemble them.
Attaching the backlight
LED backlighting is installed so that you can also illuminate the displays later in the dark.
To do this, you must first remove any existing obstacles. You have to get to the back of the scale surface.First drill a small hole with a diameter of approx. 3 mm relatively centrally. When drilling, make sure that you do not damage the scale plate on the front when piercing the hole.You can then drill the small hole to the desired size using a 6 mm drill bit.Now you can use one of the WS2812 LEDs that you have purchased or prepared with cable....into the drilled hole as shown.That's it with the installation of the backlight. Reassemble the display...and installs it in the housing.To do this, the display is pushed into the housing opening from the front. You can then fix the display on the inside with nuts.Repeat this with the second display, on which you have of course already stuck the new scale label.You can then attach the backlight to the second display.Remove any existing obstacles again......and drill a sufficiently large hole again as for the previous display.Now glue the remaining WS2812 LED in there......and reassemble the display.
Prepare connecting cables
In order to be able to control the pointer deflection of the analog displays later, they must of course be connected to a voltage source. The connection cables are prepared for this in this step.
To do this, cut off four pieces of wire about ten centimetres long and insulate the ends by about two centimetres.Tins the ends of the cables......and bend 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 cables must then be stripped of approx. five mm of insulation and tinned.The two blue wires can then be connected. They are connected to the "negative pole" of the analog display.The "negative pole" of this analogue display can be recognized by the "minus" next to the connection screw. To connect the cable there, you first place a washer on the cable......then the previously bent cable......then another washer.......and a spring washer over the connection screw.This whole "package" can then be fixed with a nut.You should tighten these "hand-tight". Bear in mind here: After "tight" comes "off." 🙂Repeat this for the other "negative pole".You can then connect the remaining "plus poles" of the analog displays to the other lines.The connected cables must now be connected to the PCA9685 breakout board.To do this, first tin the "GND" contact (on the photo at the top left corner of the PCA9685 breakout board) and the upper contacts of the "1" and "2" connection rows (on the photo in the bottom left area).At the same time, you can also tin the "GND", "SCL", SDA", "VCC" and "V+" contacts on the opposite side of the PCA9685 breakout board.You can then connect the connecting cables to the PCA9685 breakout board as shown. The (common) "negative pole" (here the blue wire) is connected to the "GND" contact of the PCA9685 breakout board. The "positive poles" of the analog displays are connected to the prepared contacts of "1" and "2".The connected PCA9685 breakout board should (so far) look something like this.In order for the PCA9685 breakout board to work, it must now be connected to the power supply - just like the WS2812 LEDs. To do this, prepare a common supply line for the LEDs and the PCA9685 breakout board. To do this, strip approx. ten mm of insulation from the individual wires of the WS2812 LED supply line.You also prepare two wires, stripping ten mm from one end and five mm from the other.Now twist the ten mm stripped ends with the wires of the WS2812 LEDs as shown and tin them with a little solder. You should already pay attention to which wire of the WS2812 LEDs is the "5V" wire. In this case, it is the wire that is connected to the red wire.This should then look something like this.Now solder the "5V" line to the "VCC" contact of the PCA9685 breakout board...Close-up of the soldered cable on the PCA9685 breakout board.The other wire of the supply line is then soldered to the "GND" contact on the PCA9685 breakout board.
Connecting the ESP8266 adapter board
The now prepared cables must of course still be connected to the heart - the ESP8266 adapter board.
To do this, the contacts must first be prepared.Tin the contacts "5V", "G", "D4", "D2", "D1" and "3V3" - as shown in the illustration.Then you can connect the "plus" line (on the photo the red and red/transparent line) to the "5V" contact of the ESP8266 adapter board.Now repeat this with the "minus" line (the blue and transparent line in the photo). Connect this to the "GND" contact of the ESP8266 adapter board.To connect the WS2812 LEDs completely, you must now connect the data line (the last remaining one coming from the WS2812 LEDs) to contact "D4".Now prepare another three five to ten cm long pieces of wire by stripping approx. 5mm of the wire ends and tinning them.The first of these three lines is used to supply the PCA9685 breakout board with 3.3V from the ESP8266 adapter board.Solder the cable to the "VCC" contact of the PCA9685 breakout board......and the other end to the "3.3V" contact of the ESP8266 adapter board.The next line to be attached connects the bus line "SCL" between the PCA9685 breakout board and the ESP8266 adapter board.Solder the cable to the "SCL" contact of the PCA9685 breakout board......and the other end to contact "D1" of the ESP8266 adapter board.The last line (after which you are finished with the soldering work) connects the "SDA" bus line between the PCA9685 breakout board and the ESP8266 adapter board.Solder the cable to the "SDA" contact of the PCA9685 breakout board and the other end to the "D2" contact of the ESP8266 adapter board.That's it for the soldering work 🙂 Your setup should now look something like this.Now you can "stow away" the electronics.Glue the PCA9685 breakout board with some hot glue in the middle between the analog displays as shown......and the ESP8266 adapter board next to it as shown. Note that the USB port of the ESP8266 adapter board must remain easily accessible because it is programmed and supplied with power via this port.And that's it for assembling the required hardware 🙂
Other variants
The great thing about the PCA9685 breakout board is that it offers up to 16 outputs. This means you can connect up to 16 displays.
A 3D printer is sufficient to produce a housing for one or two analog displays. Unfortunately, most 3D printers are too small for more than two displays. One way of combining several displays is described in the section More than two displays in one housing described below.
Case version with only one analog display.If you want to use more than two displays, you can also make a wooden housing.
More than two displays in one housing
...are difficult to realize in the way described above. At the very least, it is very difficult to print a housing with space for more than two displays using a 3D printer. Most 3D printers simply do not have enough space on their print bed for this.
At least if you want to print the housing in one part, this does not work. In case you have no problem with screwing the housing together from several parts, here is a suggestion on how the whole thing can still be realized. Unfortunately, there are currently no pictures with step-by-step instructions. I will add these here as soon as possible.
However, you can still get a very good idea of the assembly using the 3D templates. For those who still want to try it out:
A few pictures explaining the assembly can be found after viewing the required 3D files.
You can rotate the 3D view of the STL file by holding down the mouse button. You can zoom in and out with the mouse wheel.
End part of the modular housing:
You can rotate the 3D view of the STL file by holding down the mouse button. You can zoom in and out with the mouse wheel.
To assemble an enclosure with two elements, for example, you need 12x screws (e.g. M4x16) and 12 nuts. Add four for each additional element.The housing parts are then simply screwed together.In this way, an infinite number of analog displays can - theoretically - be accommodated in one housing.Detailed view.Detailed view.Detailed view.Detailed view of the front including analog displays.The gap dimensions and quality of the housing also depend heavily on the print quality of your 3D printer.Detailed view of the complete housing.
Flash firmware
Now it is time to transfer the firmware to the display.
I hope everything worked as described for you. If not or you have questions or suggestions please let me know in the comments. I will then add this to the article if necessary. Ideas for new projects are always welcome. 🙂
PS 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 think it's cool that I share the information with you, I would be happy about a small donation to the coffee fund. 🙂
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