Recreating a CRT style Radar display with a LED matrix

[rthorntn]

Update: I think this might be a bit OT, sorry about that.

Another update: Maybe the best bet is just to use 0201 LEDs real close together in a grid, like reDOT.

Hi,

I'm thinking of something like this https://www.youtube.com/channel/UCagly25EuaH5Wi1LhxUQNQg but:

• More LEDs - 360 around the circumference
• More like a retro looking oscilloscope or radar screen
• The LEDs much closer together
• Spaced to be able to draw a radial sweep http://www.radartutorial.eu/12.scopes/sc16.en.html

I cant really get my head around whether this is even possible, if I want the radial sweep to be one LED wide (1 degree) at the outside, what do you have to do to the LEDs as you go towards the centre.

I really should have paid more attention in maths.

Thanks for looking.

Cheers
Richard

[hendorog]

Reminded me of this:
https://forum.kicad.info/t/python-scripting-example-studio-clock/5387

Which might actually be hackable to do what you want.

[Z80]

Draw circles at the led spacing and distribute leds evenly around them.  There will be less on each ring until you reach the centre where there will be 1.  The line obviously won't be perfectly straight but will zig zag with leds being shared between steps, a diffuser over the panel will help smooth it out.  The challenge will be driving it, probably best to put the leds on the top and the drivers on the bottom and either implement the pattern generator locally or if you want other stuff on the screen then use a high speed serial link to the controller.

[PA0PBZ]

Can't help to think that a cheap LCD display would be so much easier...

[rthorntn]

I don't know of any big round LCDs... but a bit of waste cardboard, compass, protractor and a scalpel could fix that.

[PA0PBZ]

I was thinking about a bezel with a round hole in it, but if you need the circumference to be round it is a bit more difficult. Alibaba is full of 3.4" 800*800 displays but anything bigger will be $$ I guess.

[rthorntn]

Could you please expand on that, does aliexpress have 3.4" round LCDs?

Alibaba is full of 3.4" 800*800 displays

[PA0PBZ]

alibaba: https://www.alibaba.com/showroom/3-inch-round-lcd-display.html




edit: picture

[t1d]

RPi (cheap), plus
Video Player Program, plus
Display, of your choice, plus
Video editor software (Free/OS. Maybe run it on a bigger computer, faster/ more powerful, to create the video)

Take a picture of, or clip, or import, the beginning desired display picture. Take a separate copy, of the image, and add any features, that you like... A new radar image, an Indiana Jones style moving flight line, etc. Crop the before and after pictures, in Paint (etc.), to create the round screen, that you want. Save the first and second picture, separately. Place the two pictures, on the video editor timeline. Use the video editor's sweep transition feature to morph between the two images. Spread the sweep out, over time. Radar sweeps are, often, a transition sweep type. Create the "movie." Run it, on the RPi.

Here's my tutorial:

[james_s]

It's certainly possible. One of my FPGA projects is a 70s arcade game called Atari Subs. It displays a fairly convincing radar sweep display in the corner of the screen which is a small corner of a standard resolution raster display. I doubt it is more than a few dozen pixels wide. When the sweep is moving you don't notice that it's a little bit jaggy.

[rthorntn]

I'm thinking the "round LCD" PA0PBZ shared, connected to an RPI and stuffed in a case could be cool.  Thanks everyone.

[james_s]

It's definitely going to be hard to beat the resolution of one of those.


For lower resolution displays my suggestion would be to draw the grid of pixels out on paper and then draw each position of the sweep such that it looks as pleasing as possible. All you need is 1/8th of the radius and you can get the full rotation by swapping and mirroring the X and Y axis. No need to do any fancy math to calculate it.

[rthorntn]

Anybody got any ideas on how to get these cool 3.4" round screens, I can only see them on alibaba and I think alibaba is more about selling to companies in quantity that handle the logistics?

[Beamin]

Can't help to think that a cheap LCD display would be so much easier...

Those panels on mikeselectricstuff with a diffuser. Cost about 50$ or less.

[james_s]

I don't know about 3.4", but round TFT displays are readily available from Chinese ebay sellers.