> Hi all, I am still working on modifying the threeneurons dekatron spinner PCB > here: > http://threeneurons.wordpress.com/dekatron-stuff/variable-dekatron-spinner-kit/ > I am using an OG-4. > > > I would like to control the rate with voltage in the range of 0-5v or 0-10v > or thereabout. I have tried to implement a vactrol voltage control using the > schematics here: http://thesquarewaveparade.com/images/VtoR.jpg I tried it in > 2 place both in parallel to the pot(r18) and in parallel R13. I didn't get > desirable results on either.
I would vactrol resistor between the top (+225V) of R18 and the wiper, and adjust R18 all the way over, so its wiper is essentially connected to R15. What R18 does is vary the voltage applied to the top of R13. That voltage then charges C5 via R13. When C5 charges enough to put enough voltage across the NE2 (via R14 and Q2 to ground), NE2 fires, which dumps the charge in C5 into the base of Q2, pulsing the guide pins. Putting the vactrol across R13 should have some effect on the rate, but putting it from the +225V line to the wiper of R18 (same as the top of R13) should have a more visible effect - as long as R18 is adjusted to put max resistance between the +225V line and R13. There's a chance that your vactrol isn't being turned on very hard - you can try hooking it to an ohmmeter and seeing what the range of resistance is. The dark (no input) resistance should be high (a few megohms minimum) and with input, it should show a few ohms to a few kilohms. Note that if you hook it directly to +5 or +10 volts, it'll burn out - it needs a series resistor. I'd aim to push about 10mA through it for full on, so for 0-5V in, I'd use (5 - 2)/0.010 = 300Ω (270 or 330 would be fine) and for 0-10V, I'd use (10 - 2)/0.10 = 800Ω (820 or even 680 would be fine). - John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
