Re: IV-17 / IV-4 Smartsockets. Group input requested !
- --- In email@example.com, John Rehwinkel <jrehwin@...> wrote:
>Good tips, thanks.
> I'm probably not the John you meant, but I like to capacitively couple
> a square wave to the filament. You can adjust the current via
> capacitor size and square wave frequency, or use a series resistor.
> Try to have your filament drive frequency not be a multiple of your
> mux frequency.
I'll be looking to run the SMPS at above 20kHz, so what would be the best way to couple the filament drive to the square wave signal if the output signal from the onboard PWM module switches 5V at about 20mA ?
So far I have a 40 pin pic with 64k memory driving a Supertex HV5812 which connects to 4 multiplexed tubes, two of which are IV-4 and two are IV-17 (for comparison). The pic will eventually be changed for another one with the least required memory,to keep costs down. Vbb is 40V at 25mA. It might be possible to get the size down to as little as 90mm long and 25mm wide for a 4 tube array
I've just finished tweaking one 'segment dance' transition effect and confirmed that one tube can run one effect while it's neighbour can be running another type of effect (such as crossfading) starting at a completely different time. Each tube acts completely independently of it's neighbours, which was the hardest part of coding to get right
Now its just a case of writing the dozen or so fonts, and about as many transition effects too. (There's still room for lots more too)
I'll look at the power supply in due course, and will probably implement either P+I or FL control of the output (assuming 'differential gap' isn't good enough). The only problem with coupling the filament supply to the Vbb supply is that if the Vbb is required to change duty cycle then _both_ output voltages will change. But thinking about it some more there is most likely plenty of tolerance around the filament voltage so maybe that won't be too much of an issue ? I'll have to test it for myself.