The power supply for such circuit will be tricky, as the load will vary a lot during operation. I think that a simple boost converter won't be able to achieve enough power and due to high duty cycle, stability will be a problem. A flyback design should do the trick, however making your own will take time to achieve results. I think that a transformer looted from ATX power supply might be useful, however I didn't test one yet - in my project I'm leaving the PSU till I'm sure my digital processing is done correctly.
*Using mains voltage directly is not a viable method in music visualizers! *Keep in mind that unlike clocks, this device will be connected to an external source of audio signal. If you use mains voltage directly, then you *have to* make the input isolated. There are two reasons: 1. Your input source will likely have ground connected to earth 2. If you plug a minijack into the visualizer and then grab the other side with your hand, you're touching mains directly, and there is a good chance that it won't be the neutral wire W dniu czwartek, 22 marca 2018 13:23:24 UTC+1 użytkownik John Murphy napisał: > > I am currently working on a very similar project. Here is what I've > learned: > > 1. The IN-9 tubes don't all act properly using a 150V DC switching power > supply (I bought several different models from eBay). The glow of the tube > becomes disconnected from the bottom and "floats" in the middle - this is > not how a bargraph should behave. I have been successful using a full wave > rectifier circuit from 120V mains through a 1:1 isolation power supply > (US). If you have 240V mains, you would need a 2:1 step-down transformer. > I used the KBP307 rectifier instead of discrete diodes. Do NOT try to use > the rectified mains without a transformer. In addition to this being > dangerous, if the DC 0V has a path to earth ground, the rectifier will be > destroyed, and also likely take out other components like the uC. I am > using a Triad VPS230-110 as it's fairly inexpensive. It has a maximum > output current of 220 mA, but for a music visualizer, you won't have full > scale output on all the tubes at the same time - you could enforce this > using code in the microcontroller if you're worried about it. > > 2. Most microcontrollers have a limited number of pins that you can output > PWM on. If you want to drive 16 tubes, you need 16 PWM (or analog out) > pins. I am using two serial octal DACs (LTC1665) to drive the base of the > MJE340 transistors using the circuit in the paper you referenced. DAC > values are set with a synchronous serial stream. The clock and data lines > are common to both DACs and each one gets its own chip select for a total > of 4 digital pins needed to drive 16 tubes. > > 3. If you buy New Old Stock (NOS) tubes, some of them won't initially glow > to full height due to being in storage for so long. They need to be > "burned in" - something about the physics of the cathode tube that I don't > really understand. I have found that driving them at 15mA for about an > hour has been enough. Over that time the glow gradually creeps from about > 1/2 scale to full scale. After that, they all have worked to full scale. > > Have fun! > > Are you sure the disconnection doesn't happen because of poor filtering or inadequate driving? A proper driver should be a constant current sink, which would mean that the tube should be able to see supply without ripple (the ripple should be present on cathode as well, making the voltage across the tube constant). Maybe the supply is emitting too much noise into other circuits and your driver misbehaves? BTW. STM32 microcontrollers are a good choice, as F4 and higher series have many hardware PWM channels avaible. I'm using STM32F429ZI and as far as I remember, I can use 29 or 31 PWM channels, and there are some with up to 33 channels available. I'm planning to try the new H7 series, which have 30+ channels with PWM and there are still some timers left for other applications. Also, the FPU in Cortex-M4 really speeds up the calculations. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/45c69f04-64b9-4bd3-a2c4-f8e8d9e8bdac%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
