"The luminance is calculated passively and approximately to the following formula: 0.2126*R + 0.7152*G + 0.0722*B"

However, to quote some VGA chipset datasheet:

"With gray-summing flag set, BIOS will weight three color elements (RGB) of Color Register; and sum them to grayshade value, which is based on the formula (30% Red + 59% Green + 11% Blue)."

So, these I consider the proper RGB weights for VGA.

However, an approximate value you will be obtained with the corresponding resistors too. From these values, in a first prototype with a proto-board, I was testing with 3 variable resistors until finding the values ​​that looked best on the monitor, the result you can see in the video that I posted on youtube:

https://www.youtube.com/watch?v=DbyfIixwHSs

Come to think of it, I saw a similar thing back in the era...
Some guy had a VGA monochrome monitor which only paid attention to the Green component of the input signal.
So, red and blue objects were totally invisible.
In order to fix that, he implemented grayscale weighting using some resistors.
However, it wasn't perfect - there were some visible distortions, probably because the resistors broke the impedance matching.
But it seems you somehow managed to avoid any distortions... so, good work!

Thanks!

I do not see any distortion in the image, what does happen, especially in B & W and Ambar, is a slight decrease in intensity, but it can be solved by raising the brightness of the monitor 😀

Operating this unshielded is like operating broadcasting equipment.
Might cause costly problems if people (not only radio amateurs!) feel annoyed by the noise being aired.

retardware wrote:

Operating this unshielded is like operating broadcasting equipment.
Might cause costly problems if people (not only radio amateurs!) feel annoyed by the noise being aired.

As I said, no type of noise or distortion is appreciated.
The operation is totally normal, at least visually.

spark2k06 wrote:

retardware wrote:

Operating this unshielded is like operating broadcasting equipment.
Might cause costly problems if people (not only radio amateurs!) feel annoyed by the noise being aired.

As I said, no type of noise or distortion is appreciated.
The operation is totally normal, at least visually.

That's not what retardware is talking about. Every unshielded conductor with an HF signal on it, works as an antenna. It can receive interference, but it also broadcasts whatever signal is conducted over it. Other devices may pick up that signal and be disrupted by it. Because of that, almost every country on earth has regulations about what you may and may not transmit without a license, and penalties for breaking those regulations. The kind of signals going over a VGA connector are almost certainly not allowed and IF someone is disturbed by it and IF your local regulator operates a 'fine first, ask questions later' policy.

Now, how realistic that scenario is depends totally on where you live. Here in NL, you get a friendly visit first, then a letter and only after that do fines come into view. However in DE (and iirc UK and US as well) it's not quite so friendly.

Anyway, you avoid all that stuff by ensuring this device is inside a shielded container, which can be as simple as a cardboard box lined with aluminium foil.

Okay, now I understand. Thank you very much for the advice, I will keep it in mind for future editions.

dionb wrote:

That's not what retardware is talking about. Every unshielded conductor with an HF signal on it, works as an antenna. It can rec […]
Show full quote

spark2k06 wrote:

retardware wrote:

Operating this unshielded is like operating broadcasting equipment.
Might cause costly problems if people (not only radio amateurs!) feel annoyed by the noise being aired.

As I said, no type of noise or distortion is appreciated.
The operation is totally normal, at least visually.

That's not what retardware is talking about. Every unshielded conductor with an HF signal on it, works as an antenna. It can receive interference, but it also broadcasts whatever signal is conducted over it. Other devices may pick up that signal and be disrupted by it. Because of that, almost every country on earth has regulations about what you may and may not transmit without a license, and penalties for breaking those regulations. The kind of signals going over a VGA connector are almost certainly not allowed and IF someone is disturbed by it and IF your local regulator operates a 'fine first, ask questions later' policy.

Now, how realistic that scenario is depends totally on where you live. Here in NL, you get a friendly visit first, then a letter and only after that do fines come into view. However in DE (and iirc UK and US as well) it's not quite so friendly.

Anyway, you avoid all that stuff by ensuring this device is inside a shielded container, which can be as simple as a cardboard box lined with aluminium foil.

I added a warning in the Tindie ad and in the hackaday article:

"Disclaimer:

It is recommended to use this device inside an shielded container, which can be as simple as a cardboard box lined with aluminium foil, because although unlikely, the VGA signal could interfere with other nearby devices and depending on the laws of your country, it could lead to fines.

Therefore, USE IT AT YOUR OWN RISK."

Likewise, I will notify those who have already acquired me one or several units.

Again, thanks @dionb and @retardware for the advice 😉

Now discounted for the latest units of the PRO version:

https://www.tindie.com/products/spark2k06/monochromevga-pro/

and back in stock of Basic version, with improvements over the previous batch:

https://www.tindie.com/products/spark2k06/monochromevga/

Hi, interesting project!

I have a question: for the regular (non-PRO) version, which one will give the best Amber output, the one with the diodes or the one without?

Badscrew wrote:

Hi, interesting project!

I have a question: for the regular (non-PRO) version, which one will give the best Amber output, the one with the diodes or the one without?

The one with no diodes, but with the drawback that the color change with the switch is not good.

However, the effect of the diodes in that case is only a loss (not excessive) of brightness, but you can always adjust the brightness and contrast of the monitor.

What do you mean by color change?

Badscrew wrote:

What do you mean by color change?

The board has a switch to change color to monochrome and vice versa.

Yes, I mean what isn't good in the "no-diodes" case?

Edit: I want to buy one, just need to decide which one 😀
Particularly interested by amber output (I love the old amber monitors)

personally, the option with diodes I think is the best option. And if your amber output does not convince you, you can always short-circuit the diodes. In any case, I hope you like the result, you will tell us! 😀

This thread reminds me of WinGIF. It had an option for users of monochrome VGA monitors.
By using the standard 640x480x16c VGA driver, it was able to produce pretty grayscale pictures using false colours.

I like this !
I would be curious to see a modern OS or 3Dgame running this way 😀

nali wrote:

I like this !
I would be curious to see a modern OS or 3Dgame running this way 😀

It's a good idea, I don't have a very modern PC, but if someone has it it might be interesting to see a demo in amber mode, for example. But you can see an example of what Ghost And Goblins looks like, with the first prototype I made based on protoboard: 😊

https://www.youtube.com/watch?v=9xwnpiCaRJE