General Discussion

[muramasatheninja]

Hi,

Very excited to see this project. I wasn't sure the best way to contact you so I figured I would post an issue here.

I started on converting your hand drawn schematic.

The goal is to make a self contained board that would fit in a small enclosure.

Thanks

[muramasatheninja]

One thing I'm a little confused about is how the 2N7000 is used to add the reticule on the screen. I looked pretty closely at your video to see how you had it setup but wasn't able to spot it. Is there any reason to use a transistor over say just a switch to switch the video between the resistor and one that let's the signal straight through?

[dlcboy]

First off just let me say this is absolutely brilliant work!! I've been struggling for years to find a good solution to this problem and you nailed it, home run, out of the park! Bravo! I was actually buying the parts to build a similar albeit less capable system when I stumbled across your work searching to see if anybody had done this for the millionth time, and what a pleasant surprise to see it!

Seeing as how you have it done so well, is there anything we can do to contribute and make it better? I wondered about making a logic system for the wiimote so that it can track dots actually located at the corners of the tv so there is no need for calibration and the user can move around freely? I could try putting retro reflective stickers on the tv with an ir led light source so they wouldn't need power? I could work on sensor fusion with the wifi motion plus if you think that could be better with the help of the inertial system to increase accuracy? Your video looked pretty good already I have to say, maybe the wiimote has less noise than I expected.

Btw, muramasatheninja, imho, I suspect the 2n7000 is just being used exactly like you said, as a really fast switch... in its saturation region, just pulling the signal low briefly. Please correct if I'm wrong though!

Thanks again for the great work!! I'm anxious to get this running soon!

[ysfgary]

Hi, I would like to start this project but I am using NTSC system. Any design I need to change it before I start this project? Thanks.

[Catwashere]

Pretty sure 2n7000 is to remove saturation.

muramasatheninja, probably you could spot it because is attached to the input and output

[charcole]

Hi everyone,

First I've got to give a big apology. I never got a notification of this thread. I only spotted it because I'm currently working on a version 2 and wanted to look at my schematic. Thanks for the schematic muramasatheninja. I would add it but I don't want to produce any notifications at the moment as version 2 is quite close now (hopefully!).

The 2N7000 to dim is really dodgy and something I want to improve for the second version. I should say I'm mainly a programmer and not that great at analogue electronics. It worked but I don't think it was correct. The idea was to have another resistor in series with the video signal and short circuit it with the FET. When the FET was off the signal would go through the resistor causing some voltage to be dropped and therefore the display to dim. And when on it should let the signal through with only a slight drop in the FET.

However it's dodgy because the DC bias of a video signal is not set. It worked fine on the NES as it was about 3V. In more modern systems it tends to be 0V which means the signal is negative for half the time. When negative the current will flow through the diode in the FET and the gate to source voltage can go positive even when grounded. It seemed to work in this configuration but I wasn't very happy with it and the 2N7000 tended to die randomly and need replacing (too much current through the diode or static?). Also if the DC bias was high the resistor would cause the screen to dim more than if it was low.

For version 2, I was planning on improving this by putting the signal through a capacitor so I can fix the DC bias and then to an op-amp. This way the DC levels and driving circuitry is a known quantity. From there I can use two 2N7000s to switch between that output and a variable voltage source. This way the cursor can be more visible and there can be a pot to change between a white and black cursor.

In case people are interested, the other changes I was planning for V2, is replacing the Raspberry Pi and Arduino with an ESP32. It has bluetooth built in and I have it working with a Wiimote (it works a lot more reliably than with the Pi too as a bonus). The ESP32 is dual core so the other core can be used to do the precision timing needed to pick out parts of the frame (what the Arduino used to do). However the ESP32 also has a peripheral that should be able to do it without much CPU time so that's what I'm planning to use. Finally I'm going to use a 555 timer to use the dimming signal and the output from the comparator to flash the LED so the ESP32 don't need to listen to the white level like the Arduino did. Tested everything in stages, just need to go through and build it up. In all it should be a much neater product and have better tolerances than the old RPi/Arduino method.

Thanks,
Charlie

[charcole]

dlcboy: Zero calibration would be good. I'm wondered about adding four IR LEDs to the corner of the TV. Problem would come if the system could only see one LED and it wouldn't know what corner it was seeing. You could try and keep track of the points (last time I saw one around here it was the top left LED). Your idea of using the accelerometer could add some more data to this to make it more accurate. Or the micro could control the LEDs and flash them in sequence if unsure which it was looking at. It's something that's on my mind but will try and get V2 working first. It'd just be software from then on.

ysfgary: Hi. NTSC would be cool. I think the only thing that'd need to change would be the timings and the line number calculations. It shouldn't need hardware changes. Might be worth waiting for V2 now though.

Catwashere: Good spotting

[Catwashere]

Can't wait to see V2 and see if you convince me to buy an ESP32.

Please this time put the schematic hahahaha.

[Greyneon]

Was looking at this about a week ago or so and now i hear about a version 2?

I am SO subscribing to this!

[muramasatheninja]

Thanks for the update. Definitely looking forward to Version 2!

[charcole]

Another quick update for you all. Got the Version 2 working at the weekend on strip board. This is the new analogue board with the ESP32 handling Bluetooth (for Wiimote) and generating the video overlay. Video overlay stability is a lot better this time around. Next steps are to make a schematic (probably in KiCad) and layout a PCB so it can be sent off to be fabricated. Hopefully that shouldn't take too long.

[Greyneon]

Awesome news! Can't wait :D

[Catwashere]

Me too

[charcole]

Another update for you. So, last week I finished off laying out the PCB and sent it off to the fabricators. Expecting the first batch of boards back in the next couple weeks. From there I just need to assemble them to ensure I didn't mess anything up and improve the software side of things ready for release.

[dlcboy]

Awesome work!! I'm so excited to see this moving along!!!! When it went quiet I had thought you might have moved on to something else. I tried and tried to get wii library support working on my pi and just failed, so I'm super excited to have something that's more robust and a bit more dedicated to this one task (which I will be using 100% of my free time of course;) are you making a handful of boards? Can I help in any way? I'd be happy to assemble or solder if you are doing it yourself. Also happy to help by donating enough beer to the cause to make it less painful too;)

I can't wait to get one running to try out different sensor fusion schemes, and becon setups. I feel like it's pretty important for these old games to have dead on accuracy with minimum latency. Keep up the good work!! I can't wait to have duck hunt on my giant 2016 hdtv:D

[charcole]

Thanks. Yeah, didn't have much free time the past year or so due to work but hopefully will start doing some more home projects again. I'm sure I'll have messed up something on these first batch of boards but if not I'm happy to send any left over unpopulated ones out if anyone wants one. I've just had confirmation they should get delivered on Thursday. As for completed boards, if I decide to sell some the PCB fabricators should be able to do almost all the assembly for a pretty reasonable cost but thanks for the offer. Whatever I do or not though, everything you'll need to build one will still get added to github.