Andrew Davie's Arduino Televisor by Chris Lewis

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Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Wed Jul 15, 2020 6:39 am

Construction Diary 1 Introduction
I was particularly impressed by the work carried out by Andrew Davie and Keith Colson with regard to construction of a disc based televisor based on a low-cost Arduino microcontroller. Obviously, I don’t possess CNC machines to manufacture discs or fancy laser cut components so armed with a few hand tools in a kitchen table workshop I decided to build one myself utilising the clubs 12-inch laser cut stainless steel disc and standard club motor. I do recommend access to a decent oscilloscope for setting up the sensor.
Unlike the conventional televisors the NBTV WAV files are stored on a micro SD card and all the functions are controlled from a miniature touch screen display. Included is an audio section which feeds an external loudspeaker.
A central board designed by Andrew contains all the necessary interconnections to the external devices. These include
External dc power supply
Supply for infra-red source LED used for disc speed detection
Motor supply
Output to Matrix LEDs
Input for speed detection
Serial connections to external TFT touch screen display.
Further sections of this post will outline my progress during the final build.
Attachments
plate 1.JPG
Completed Unit
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Wed Jul 15, 2020 5:45 pm

Construction Diary 2 The enclosure
We need some sort of housing for our televisor so I tend to opt for construction using softwood strips and chipboard for the panels. This affords some protection but allows one to demonstrate the internal workings. One thing to watch is danger from the spinning disc which is effectively a ‘bacon slicer’ in disguise. The following posts will show my unit being rebuilt after being varnishing with a clear polyurethane coating. All the material used was bought from the B & Q warehouse here in the UK. If you buy the sheet material from them, they will cut it to size for free if you are concerned about doing this at home.
The crossmembers are used to mount the motor, display and speed sensing devices.
Attachments
IMG_2874.JPG
The enclosure
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Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Wed Jul 15, 2020 9:34 pm

Construction Diary 3 Display preparation
Andrew has used a Nextion NX3224T024 - Generic 2.4" TFT LCD Touch Display for the televisor an Human Machine Interface (HMI). These are available from various sources including eBay. They are used extensively as an interface between Arduino and Raspberry PI projects due to their easy of use. There are only four interface connections to the display, zero and plus five volts and transmit and receive signals.
This stand-alone display has on-board intelligence whereby the graphics can be configured by a text editor. An on-board microSD card allows us to load Andrews HMI software onto the unit.
The latest software for this project is located at https://github.com/andrew-davie/ArduinoVisor
First thing we need to do is get hold of a microSD card. There are different versions but we need a class 10 card as we will need this later for the control board for real time data transfer of the NBTV video signals.
Firstly, we need to format this card and load a file presently named ‘nbtv3.tft’ from the github depository as shown above. Initially the MicroSD card will need formatting. You will probably need a MicroSD adapter for your PC either a USB or an adapter card. Free formatting software can be found at https://www.sdcard.org/downloads/formatter/ , after which the .tft file will need loading into the root directory with no other files loaded. The next step is important as it can damage the display.
Place the microSD card into the slot on the display card. Using the miniature USB adapter board supplied with the display connect up the positive and negative connections to the board. Power up the display from your commuter’s USB port and Andrews HMI software should load after a few moments. Upon completion his graphical display should be displayed. The MicroSD card can now be removed. Beware that the touch screen is not operational until it is connected to the main board.
Attachments
jkj.jpg
jkj.jpg (31.36 KiB) Viewed 1306 times
612+fY6eSvL._AC_SY355_.jpg
612+fY6eSvL._AC_SY355_.jpg (20.75 KiB) Viewed 1306 times
Nextion_Power_Supply_Test_Board_1_.jpg
IMG_2821.JPG
A resounding success
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Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Thu Jul 16, 2020 6:10 am

Construction Diary 4 Light Box construction
In order to produce a display a modulated light source is required behind the disc. With the advent of modern LED technology very bright light sources can be produced by LEDs in the place of conventional filament lamps. As such small aperture’s exist in the rotating disc a very powerful light source is required. On my televisor I am using lighting arrays used for internal car illumination. These very bright LEDs work off twelve volts and each display has a surface mounted series resistor to attain the correct current for the display module. I have used three units in parallel in my light box These units are surprisingly cheap can be found on eBay and have a self-adhesive strip on the back for ease of mounting. PLEASE DO NOT LOOK DIRECTLY AT THEM WHEN ILLUMINATED. In front of the light source I have fitted a diffuser
Attachments
IMG_2891.JPG
Completed Light box
IMG_2892.JPG
Internals
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 1:51 am

Construction Diary 5 The Central Controller Board

This excellently designed board forms a hub for all external devices connected to the main computer controller. I am particularly impressed with the fact that all interconnections terminate on the board with no external ‘linking’ of common points. The heart of the board is based on a standard Arduino Micro (ATMega32U4) which is pre-programmed with the televisor code.

Connections to the board have been reported earlier. Keith Colson has suggested some enhancements described in his construction diaries
viewtopic.php?f=35&t=2465&start=15

To get mine up and running all, I needed to do was remove twelve volt LM2596 dc to dc convertor pack and bypass the output out positive supply to the input. As my motor was drawing a lot of power from this supply it was causing output distortion which was detected on the matrix display during playback as these share the same supply.
Whilst commissioning my televisor I experienced problems with the external speed detector components. Initially I increased the value of R3 to about 180K but had difficulty getting reliable synch pulses so in the end I opted for an external ‘active’ IR sensor which provided me with a ‘clean’ synch signal from the disc.
Attachments
goldenratio3.jpg
PCB Layout of Control Board
goldenratio3.jpg (263.39 KiB) Viewed 1277 times
pcbway1.jpg
Fully Populated Control Board
pcbway1.jpg (367.02 KiB) Viewed 1277 times
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 2:11 am

Construction Diary 6 System integration part A

Now follows a step by step guide to building up the televisor. You will notice temporary cable twists to secure wires in cable cradles. Firstly, mount the board securely using PCB pillars. Observing polarity connect up to external dc supply connector. We strongly recommend using 1mm2 10Amp cable to reduce Voltage drops
Attachments
IMG_2881.JPG
Power supply connections
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 2:33 am

Construction Diary 6 System integration part B

Next, we are going to connect the remote LCD display to the main board using the text on the board.

Red +5 Volts
Black GND
Yellow TX. (transmit)
Blue RX (Receive)

We can now power up the control board from a suitable 14 to 21 Volt two Ampere capability dc supply. We should now see the home screen on the display and, if we touch the screen should see the ‘play list’ menu. We should be able to scroll down using the slide control on the left hand side of the display.
Attachments
IMG_2882.JPG
Wiring to control board
IMG_2884.JPG
Home page
IMG_2885.JPG
Play list Menu
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 3:53 am

Construction Diary 6 System integration part C

The addition of a 4 to 8 Ohm speaker
Attachments
IMG_2888.JPG
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 5:22 am

Construction Diary 6 System integration part D

The addition of an infra-red LED source. The long lead on the LED is the positive connection. Here soldered to an offcut of stripboard for ease of mounting on the crossmember. R2 (180 Ohms) restricts the current flow for it and feeds from an on-board regulated five Volt dc supply.
Attachments
IMG_2890.JPG
Addittion of IR emmitter LED
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Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 5:35 am

Construction Diary 6 System integration part E

The addition of the motor and LED Matrix. The motor is mounted here using a ‘terry clip’. As the motor is a potential electrical noise source it is good practice to twisted cables and segregate from other electrical connection cabling.
Attachments
IMG_2894.JPG
Addittion of LED Matrix and Motor
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 5:42 pm

Construction Diary 6 System integration part F

The final component required is an infra-red detection diode. Here I deviated from Andrews design. Normally you would connect up a standard diode here but I had trouble getting a consistent synch pulse so I opted for a commonly used Arduino interface card with an on-board voltage comparator and a pre-set pot so I could get a nice clean output synch signal. Please be aware on the PCB the connections are transposed. The connection marked negative is actually positive and visa versa. If you are using an IR receiving diode remember this. Anyway, my device has three wires. Zero and output go directly to the PCB whilst I pick up the positive five volts supply to feed the unit from the junction of R2 and 3 on the PCB (orange cable).
Attachments
IMG_2896.JPG
Detector fitted to Televisor
det.jpg
Detector Board
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby Andrew Davie » Fri Jul 17, 2020 8:21 pm

Thanks for the info on your build. I'm watching keenly.

Regarding the IR detection - I spent about an hour trying to adjust which hole I had taped-over and which was un-taped for use as the IR hole. I could not for the life of me get any but my original untaped hole to work. Eventually it clicked - I had (years ago) put tape over BOTH sides of the holes. It had not even occurred to me to look, so when I was "moving" which hole I was using, I was effectively leaving the disc with NO holes.... explaining why it ran away to supersonic speed. Anyway, all good now :). Strange that you have so much trouble with noise on the IR... mine looks very very clean to me.
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 9:11 pm

No Problem Andrew,

I assumed you were using your own disc with only one synch hole but it appears you are using a standard disc and covering 31 of the 32 holes. Yes it takes a little time to select the correct hole to leave exposed. I am using the clubs 12 inch standard stainless steel laser cut disc. I used black insulating tape to mask 31 of the 32 holes. When you get the thing running and synchronised you can determine how many holes to advance or retard by experiment.
Attachments
IMG_2907.JPG
Here is poor old Debbie with the synch hole approx. 180 degrees out of line.
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby Andrew Davie » Fri Jul 17, 2020 9:25 pm

My disc was made by Peter Yanczer, a club member who passed a few years ago, I think.
At first I was not at all impressed with it, and pretty much said so - much to my regret. It's not a bad disc; but at the time I thought it was rather worn/used looking and effectively secondhand. It wobbles a bit (being very thin), but does produce a rather good picture. I hand-filed the scan holes one by one to get the "perfect" picture.
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Re: Andrew Davie's Arduino Televisor by Chris Lewis

Postby acl » Fri Jul 17, 2020 9:35 pm

Yes Andrew,

These standard discs are in stock at the moment so I used them in case anybody else wanted to build one. One problem I did encounter was 'splash' from the laser cutter producing dark vertical lines on the display. I have a set of very fine drills and managed to carefully clean each of the 32 spiral holes by hand and rub fine glass paper over the side of the discoloured side of the disc and the quality of the picture greatly improved.
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