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! On Wednesday, March 21, 2018 at 3:52:45 PM UTC-4, Mikołaj Walkowiak wrote: > > Hello everyone! I'm doing project for college and I've decided to make an > audio visualiser using IN-9's. The problem is I don't have any idea how to > power them. I'd like to have 18 tubes for different sound frequenties and > I'll be using stm34 to calculate the value each tube should show.. > > Now, I know I need 140v and 0 - ~~12 mA for 1 tube but that's all I know > honestly. I think I'll use something like the 0-offset driver found in > HERE <https://www.die-wuestens.de/rd/IN9-2.pdf> controled by PWM of my uC > but I honestly have no idea how to power them. Is 140V(or 150V? everywhere > except there it says 140V) enough even for 18 tubes? If yes is it possible > to make this kind of supply myself as I can't find anything reasonable > price-wise with 140V. Do I need to consider anything else? > -- 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/3a61dbd3-90ff-4052-b51b-edcdabe2ffbd%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
