Do-List

A "new fashioned" televisor, using an Arduino to drive the motor and display.

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Do-List

Postby Andrew Davie » Thu Jun 08, 2017 10:42 pm

Thought I'd do a do-list and try to keep it up to date. At the moment it doesn't feel like a lot, but might help to write them down.


  • Build a 12V LED Matrix. I have bright-white and also orange LEDs, so perhaps one of each
  • The disc speed code (PID) is still dodgy when first spinning-up. I'm going to test a much more basic "if it's too slow go faster, if it's too slow go slower" approach. Although the PID is lovely, the problem it has is that if it kicks in when the disc is too slow, then all that time taken getting up to the right speed then has to be compensated for, and it tries to go super-fast to catch up. Big oscillations when it's pretty clear I could/should just say "hey, you're overspeed, slow down!". It keeps speeding up to "catch up" due to the integration. So, have a bit of a play with alternate "hardwired" solutions. This may also fix the (very) rare occasion where the disk is stuck on "stopped" until you give it a manual kick. I modified the code somewhat, and it now seems to be fixed. Still using a PID.
  • Waiting on my prototype IC boards. They're probably about a month away. I had 10x IRL540 and 10x IRL540N arrive today, and waiting on some TIP122 and TIP31. I will have more than enough components by the time the boards are done. Found a place in the USA that will do 10x boards for $5 (!!!) + $28 shipping, which is really reasonable.
  • Design/print a 3D printed disc built out of multiple parts with some sort of jigsaw connector to snap together accurately.
  • test the new mini-motors that arrived. I'm hoping that they're powerful enough, yet quieter. They're quite small. Tiny actually.
  • awaiting arrival of toothed belt and pulleys. Want to test driving the disk using a toothed system instead of a friction band
  • Build a pretty "case" for the entire thing. This may also require input from the museum as to what's suitable for a hands-on display. If it goes that way.
  • Do I need a better sound system? Dunno. Maybe. What's next after the simple RC filter?
  • Generate "info" screens for all the videos I plan to have on the SD card
  • resample/rework all videos for optimal clarity and synchronisation with sound
  • fix (or remove) shifter code that allows frame positioning U/D/L/R via UI
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Andrew Davie
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Re: Do-List

Postby Steve Anderson » Fri Jun 09, 2017 9:38 am

I'll only comment on the RC filter...you could improve it by adding one op-amp, but as your PWM is at 180-odd kHz I really don't think it will make any difference. But if you want to go that way I'll quickly knock up a design. Your biggest improvement to sound will come from housing the speaker properly, having it rattling around on the bench is no way to judge its capabilities - as per Klaas's comments previously. Even cheap multi-media speakers are enclosed in a box to 'improve' their sound.

In another thread r.e. temperatures, they all seem fine. If you touch a component and have to remove your finger in less than two seconds - that is too hot. Tubes/valves excepted. Sitting on an open bench all may seem fine but once enclosed in a case things could be different. A plastic case is thermally not very conductive and the insides could reach 30 Celcius above room temperature. If used in a hot country (here) where the ambient often goes above 40 Celcius that takes the components to 70 Celcius which is the upper limit for commercial grade components. PCs have fans for a reason. This shouldn't need a fan, but if it's going to be a long-term and reliable exhibit you do need to think of these things.

Another point, if this is eventually to be a display open to the public it's going to need to meet all the applicable electrical safety standards. This can be a tough hurdle to overcome. Your best bet is to use pre-made and certified power-bricks (US, wall-warts). There is also the mechanical safety to consider from rotating disks, motors and the like. It only takes a kid to get his/her finger stuck in a toothed belt and you've got a lawsuit on your hands.

Steve A.
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Re: Do-List

Postby Andrew Davie » Fri Jun 09, 2017 10:31 pm

Steve Anderson wrote:I'll only comment on the RC filter...you could improve it by adding one op-amp, but as your PWM is at 180-odd kHz I really don't think it will make any difference. But if you want to go that way I'll quickly knock up a design. Your biggest improvement to sound will come from housing the speaker properly, having it rattling around on the bench is no way to judge its capabilities - as per Klaas's comments previously. Even cheap multi-media speakers are enclosed in a box to 'improve' their sound.


OK, noted. Thanks for the offer - I'll stick with what I've got and wait until mounted inside something before making any decisions to modify.

Steve Anderson wrote:In another thread r.e. temperatures, they all seem fine. If you touch a component and have to remove your finger in less than two seconds - that is too hot.


Nowhere anywhere near that. Quite warm to the touch but not even approaching uncomfortable.

Steve Anderson wrote:IAnother point, if this is eventually to be a display open to the public it's going to need to meet all the applicable electrical safety standards. This can be a tough hurdle to overcome. Your best bet is to use pre-made and certified power-bricks (US, wall-warts). There is also the mechanical safety to consider from rotating disks, motors and the like. It only takes a kid to get his/her finger stuck in a toothed belt and you've got a lawsuit on your hands.


We're not quite as bad as the USA here, and lawsuits are unlikely. However, my plans already include a power-brick, which I have handy. I might even switch over to it this weekend, leaving just the LEDs powered via an accessible transformer. That will then speed up my plans to convert the LEDs to 12V too. As to the rotating disk, yes very dangerous. I already talked to the museum guy about this and he even offered to possibly fund making it safe for display. I think enclosing the entire disk in a plastic enclosure (form-fitting I hope) would make it pretty safe. But that's all a long way in the future, anyway.

I recall accidentally poking a pencil in the disk when it was rotating. Flew out of my hands at speed, and took me half an hour to find where it had gone to!
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Re: Do-List

Postby Steve Anderson » Sat Jun 10, 2017 4:07 pm

Chris Long built a NBTV display item for a museum in Melbourne a few years ago, the photo shows how the public were kept safe. I don't recall which museum it was and can't find any text either, but the photo's file-name may be a clue. Either that or get in contact with Chris directly, sadly I don't have his e-mail address. There may be a link or address within these pages...

http://www.modulatedlight.org/

Chris had no sync problems as both the camera and monitor discs were mounted on the same long shaft, the camera disc can just be seen at the far end of the case. It was a demonstration of the principle rather than a separately located camera and receiver.

Steve A.
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Re: Do-List

Postby Steve Anderson » Sat Jun 10, 2017 4:41 pm

Here's a better view during construction on his dining table. The large wooden box contains most of the electronics.

The result? See photo of Lionel...basic mechanical sketch also...I think this was a sketch he had to do and submit to the museum during the application/approval process...

Steve A.
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Lionel3NM.jpg
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NBTV_MODEL_DIMENSIONS.gif
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