vacuum fluorescent display - tranistor control?

Other Hardware General Electronics
1

Hello

I am trying to get an Arduino Genuino 101 (3.3v logic) to control a Vacuum Fluorescent Display, this is an old Samsung display salvaged from a DVD player.

I have found I can get elements of the display lit up with 3v DC applied across the Cathode, and +12v applied to the Grid and +12v to one of the elements on the Anode, as you can see in the image below:

I am wanting to control the grids and elements with transistors, not with a VFD driver as I have lots of transistors. Here is my current test circuit to illuminate a single element:

The element comes on, but does not switch off. The element only goes off when I disconnect the collector of the transistor from the arduino. Connecting the collector to ground or the 3v3 supply on the arduino the VFD remains on.

I am using two power supplies with the grounds connected together as well as to the arduino.

I think I've missed something, can anyone help?
Thanks
Karl

2

karl101:
I think I've missed something, can anyone help?

Sure did!

Look at your circuit. When your 3.3 V Arduino output is HIGH, just what voltage is it? What will that do for the PNP transistor on the 12 V line?

3

You need to level-shift to 12V before driving the PNP. You meant base resistor, not collector.

4

Hello
Thanks for the pointers, I've added a NPN transistor to level shift, and now have my test circuit working as expected:

Thanks again
Karl

5

If you are going to use that current driver circuit, you no longer need the 100k.

6

Paul__B:
If you are going to use that current driver circuit, you no longer need the 100k.

Excellent, thanks for that.