> When I connect the emitter to to +13v, base to ground or +5 through > any resistor and collector to the array, it lights up. Only when I > disconnected the resistor (open), does the array turn off.
Right. You'd have to pull the base to +13V to turn it off. Something lower (more negative) than +13V, such as ground or +5V will turn it on. We have the same problem with anode drivers for nixies, but at 180V instead of 13V. The usual approach is to use two transistors wired as a level shifter. Pretty much any of the anode driver circuits posted in this group would work for driving your LEDs too. > I have tried base resistors from 200 ohm to 200k ohm, and the same > deal. When I use +5v on the emitter, however, the circuit works as it > should. Yup, as long as the base is not more negative than the emitter, the transistor will turn off. With the emitter at 5V, putting the base at 5V will turn it off. In short, you basically need two transistors to do high-side switching like this, unless you float your logic so that it's 5V supply is common with the LED's 13V supply (note that then, the "grounds" must be separate, as your logic ground will be at 8V, from the point of view of your LED's ground). - 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.
