On Tuesday, December 3, 2013 2:24:03 AM UTC, Chill4844 wrote: > > I am attempting to use an Arduino in conjunction with a > TLC5940<http://www.ti.com/lit/ds/symlink/tlc5940.pdf>to drive an array of > IN-9's (And not kill myself or blow anything up) the > problem being if i understand it right (which I probably don't) is that > instead of a positive PWM out the arduino the TLC5940 works by sinking the > current on the cathode side. I don't think i can use this with my standard > mpsa42 (and I'm not going to attempt anything until i get some advice) I do > have some mpsa92's available. > I don't think you want the PWM capability of this chip for IN9. For what you're trying to do, take a look at the TLC5628 which is an 8 channel DAC with a simple 4 wire interface to the microcontroller. Hook the output of each DAC channel up to the simple MPSA42 current sinks per Jeff's paper, and that's all you need. You can manage around the Vbe offset in software to keep the hardware simple. That's the technology which sits behind this: http://youtu.be/mQ1567EFCY0 Grahame rolled his own version and documented it here ( http://www.sgitheach.org.uk/ss.html) including a full schematic. BTW, IN9 are very variable and suffer a lot from cathode poisoning. To get an array of them to perform consistently well and in a uniform way is going to take quite some tube selection and conditioning. IN13 may be a better bet, though they are rather dim to my eye. Cheers, Jon.
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