GreenAntz RGB to component transcoder

[PL1]

I'm guessing that Scott already knows this.

Uhhh . . . not really.  You're working FAR beyond my very basic skills in electrical engineering.   

The idea of using a PIC with built-in VCO and comparator functions to control a logic gate that turns sync processing on/off sounds promising.

Seems like the safest approach is to have the default state for that logic gate turn sync processing off and turn sync processing on only when a 15kHz signal is detected.


Scott

[Zebidee]

I'm guessing that Scott already knows this.

Uhhh . . . not really.  You're working FAR beyond my very basic skills in electrical engineering.   

Oh noes, I rely on you to call me out on my ---That which is odiferous and causeth plants to grow---!

Everything I know about electronics has been self-taught, mostly since taking up this hobby and much more since retiring. Well, I have a strong computer, science and tech background, so not entirely illiterate I guess.

The idea of using a PIC with built-in VCO and comparator functions to control a logic gate that turns sync processing on/off sounds promising.

It does, doesn't it? Not just this project - with a PicKit and a logic analyser you can do a lot of stuff. If you can do it with an arduino then you might be able to do it with a PIC or some other programmable micom instead. Smaller cheaper. Programmable microcontrollers are common in modern (and not-so modern) electronics.

But for now I'm sticking to old-skool analog electronics to get the job done.

Seems like the safest approach is to have the default state for that logic gate turn sync processing off and turn sync processing on only when a 15kHz signal is detected.

Aye it does. In addition to the LMC567 (SOIC-8) I'll use a SMD transistor or mosfet to do the V+ switching (both same SOT-23 footprint, and I have ordered both, so all good). I just have to turn on/off the final sync amplification & buffering stage, which draws only a little current, and incidentally powers the sync LED so I can delete the sync filter I'd setup for that earlier.

So, waiting for parts. I will then breadboard it, but I'm so confident enough it'll work that I've already redesigned the PCB.

[MdH]

Adding a message so I can send a PM

[Zebidee]

MORE MORE SYNC


Over the past month or so I've been working on solutions on blocking non-15khz video signals.

Thirdly, it will BLOCK higher frequency signals (VGA, 31khz+) automatically (optional, but on by default). I hope so anyway, because I haven't tested this last part yet

Doing this with purely "analog" components proved to be a big challenge, and I wasted time exploring several dead-ends before finally getting to a reliable solution. Even so, I learned a lot from this exercise.

I asked AI for help at different times. Occasionally it did help by giving me a different perspective, but mostly (80-90%) it just led me down garden paths that led to nowhere. It can make mistakes too, sometimes silly mistakes, so use with caution.

"Filtering" out frequencies >15khz was a false hope. Not impossible, but completely impractical.

Better approach is comparing frequency cycles (hertz) via a tuned-in phase-locked loop (voltage controlled oscillator). It works much better because you don't have to filter anything out, just compare PLL with input frequency patterns. If they are a match then it "unlocks" and you're in.

At first I thought I could do this with a single IC, and was trying to do so with the tireless LM567/NE567/LMC567, a tone decoder that has been around almost as long as I have (>50 years). It has been used extensively in the telecommunications industry for tone dialling and other such. Being an industry stalwart (like myself!), it has been copied and cloned and reinvented many times (also me!), but mostly appears in a 8-pin DIP-8 or SOIC-8 or SOP-8 packages. One variant is optimised for low-power (LMC567), but it also requires different external components so this makes testing and prototyping messy. Often I didn't know what the IC i was working with expected from me, but I muddled along and eventually worked things out. But it still wouldn't lock-in on the sync signal input.

Finally I realised that the 567 wan't locking-in because this video sync input is mostly HIGH (~93%), with only briefly pulses LOW  (7%), and the 567 expects to see input frequencies with a duty cycle closer to 50%.

So I had to introduce another IC, the famous LM555/NE555/TLC555 to "square-up" and "fatten" the sync pulses before feeding them into the '567. The '555 is of the same family as the '567, of similar age, and also comes in the same 8-pin packages (DIP-8, SOIC-8, SOP-8).

The '555 is much easier to work with than the '567, but fattening the sync still presented some challenges. One of these was that I couldn't just output a pure 50% duty-cycle output to the '567, because that would effectively turn 31khz into 15khz and then it would erroneously pass the PLL lock/key test.

Instead I settled for a duty-cycle of about 40% from the '555. These fattened pulses maintain original frequencies (e.g. 15khz, 25khz, 31khz), and the '567 only unlocks it's output pin for a true 15khz signal input.

I will post on this in more detail later, but wanted to put something up now because I'm pretty excited that this is working out.

Sorry this post seems long. Really only skimmed over the details, was trying to be brief.

Some more testing to do, but I hope to include this functionality into GreenAntz soon. I can also foresee a bunch of other applications for this in our hobby space.

I have linked to a very basic, short video (click on the picture below). Watch the LED on the breadboard. If I can turn an LED on then I can do anything 

[almsivi]

Very cool, i have to post once to message you to get one right? Here is that.

[Zebidee]

Yes, exciting times to be ordering a new GreenAntz, as I am completely re-working the sync circuits atm.

The new GreenAntz will be able to handle whatever sync polarity you give it. It will also check for a valid 15.7khz signal, with a capture range of about 1khz either side. If this signal is absent GreenAntz will automatically cut the sync and video feed, so no chance of damaging sensitive CRTs. The sync LED will indicate sync status.

I still have GreenAntz v2.2 available, at the old price of US$50. Please PM me.

The new GreenAntz (I haven't decided on version number, name yet) price will likely increase slightly as it offers increased functionality, and includes more costly ICs. I also need to get those enclosures sorted out, now that Ond has done the design work. I really should have got some printed already but the sync re-vamping stuff has been taking all my attention.

Very cool, i have to post once to message you to get one right? Here is that.

[almsivi]

Thank you for the exciting update! I sent you a pm and look forward to getting to experience both! If my pm didn't go through for some reason shoot me one and I'll respond back. New to this forum still.

[wr023]

also first post here, eagerly awaiting the new version when it's ready

[Zebidee]

GREENANTZ SYNC WINS

Success! The latest assembled prototype works well and meets all of my established goals.

I am proud to announce that the *NEW IMPROVED* GreenAntz v2.3 "Sync-off Ant" superior sync circuit will:

- accept all sync input polarities (-/+) and combinations of polarities.
- automatically process composite sync input including CRTEMU csync (which does not switch off the vertical sync signal).
- automatically analyse, filter and block sync signals that are not 15.7khz (within a bandwidth of approximately +/- 1.0 khz).

Which means I am delivering on my earlier promises, in particular:

Thirdly, it will BLOCK higher frequency signals (VGA, 31khz+) automatically (optional, but on by default). I hope so anyway, because I haven't tested this last part yet

This is a major upgrade from the older GreenAntz versions! I am considering whether to increment version number to v3.0.

The new design replaces 2 small 5-pin ICs (logic gates) with a 3-pin MOSFET for power switching, a 16-pin quad-logic IC for the csync processing, and 2x 8-pin ICs for the 15khz filtering. There's also a bunch of extra capacitors and resistors involved in trimming, buffing and tweaking signals. Fair bit of stuff.

All this extra hardware has used up most of the spare PCB space and added a bit to the production costs.

Since my last posts I have:

- created a fresh breadboard prototype of the sync and filter circuits
- fine-tuned that circuit
- tested circuit with various parameters (component values) and components from different manufacturers
- designed and built a PCB prototype
- comprehensively tested the new PCB prototype

Here is a pic of my final (fourth) fresh breadboarding of the circuit, from forming composite sync to filtering the 15khz to switching the power on (lighting the LED). This made it easy to swap out and test different parts.




 
The filter is a phase-locked loop based design, which works similar to a lock & key basis. The frequency patterns must match. It requires high-precision parts in order to get the frequencies and wave patterns right. It has a target of 15.7khz with a bandwidth of approximately 2khz (+/- 1k).

Before I forget to mention, there is also a 15khz filter override switch if you decide you want to ride bare-back for fun, or perhaps you want to use GreenAntz to connect to a compatible HDTV in 640x480p (which is possible).

In case you are wondering, this is the same technology that would have been used in the Matrix to dial in/out (that is, in old-skool tone-dial telephones).

Anyway, I managed to squeeze all of that into the remaining PCB space on the GreenAntz, without disturbing parts like LEDs and screw holes that the enclosures are already designed for. Here is a pic of my first completed GreenAntz v2.3 "Sync-off Ant":


 




I also made a short video demonstrating how this 15khz filter/screen works. Sorry that it is a bit dark, I needed to make sure there was no screen flicker and that the blue LED was clearly visible (and that my messy work area was not). You can rate my narrative skills as I provide a commentary to help you follow the fun





Overall I would call this a complete success! The new design does exactly what I wanted it to do.

Here is a revised "State of Play" summary table of different transcoders. As you can see, GreenAntz v2.3 "Sync-off Ant" outperforms them all.




The only surprise issue I've encountered is that: if you change the polarity of either sync signal to positive, while the GreenAntz is connected, the "Sync-off Ant" sync circuit will fail to reset itself and process the new sync input until you manually reset the GreenAntz (that is, unplug, or turn power off and on again). This never came up during breadboard testing as I always disconnected it to change sync parameters. People are unlikely to encounter it, and anyway is simple to resolve.

It is perhaps worth mentioning that, because of the PLL design, the 15.7khz filter will also pass frequencies at (2n+1)*15.7k, where n=0,1,2 etc. This means at 47.1k, 78.5k, 109.9k, 141.3k and so forth. This seems unlikely to be an issue for most people, but so you know. I may, with future versions and PCB space allowing, include a low-pass filter to exclude those higher frequencies altogether.

If you would like to order, please message me directly. I currently have just a handful of GreenAntz v2.3 "Sync-off Ant" PCBs available from this batch for only US$55 each + courier delivery (+$17 to USA including import duties). Prices will undoubtedly go up soon, and the purple PCBs are sooooooo cool, so locking in a purchase now is a good idea   

Enclosures will also be available soon, depending on the quality of what I get back from the 3D printers. The first small batch have already been printed to Ond's design and should arrive any day now. I am reluctant to offer them for sale yet until I give them a proper quality check. So here's a deal: if you order a GreenAntz "Sync-off Ant" right now, I will include a free enclosure with the first four orders (I have already received one pre-order, so that leaves three more). Assuming they pass quality check, of course

If you want to save some money and order a GreenAntz v2.2 instead, I still have some available for only $US50. The new cases will work for them too   

[srchrono]

Really excited about these! I just wanted to post so I can DM for one. Thanks!

[shinobicalamity]

I just wanted to post too, because I'm intrested to order v2.2 so I can DM:)

[Zebidee]

Enclosures will also be available soon, depending on the quality of what I get back from the 3D printers. The first small batch have already been printed to Ond's design and should arrive any day now. I am reluctant to offer them for sale yet until I give them a proper quality check. So here's a deal: if you order a GreenAntz "Sync-off Ant" right now, I will include a free enclosure with the first four orders (I have already received one pre-order, so that leaves three more). Assuming they pass quality check, of course

All free enclosures have been claimed. No more free ones.

Also, they're taking a bit longer than I expected to arrive, which affects everyone.

If you want to order a GreenAntz v2.3 with an enclosure, probably best to wait. Keep monitoring this thread, I will post developments over next for 2-3 weeks.

Apologies to those affected by the delays