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!