I need to drive a large seven segment display (segment length is a about 2 inches) using a micro-controller (PIC 16F877). I've driven normal seven segments directly from PICs without issues, but I found that 5v is not enough to drive this one. It needed something around 9 volts *(is this normal?)*

So what came to my mind is this. *(Designed using Proteus ISIS 7 Pro)*

![](https://i.stack.imgur.com/wqQgi.png)

I've supplied 12v to this circuit and used the **RV1** preset to adjust it (to make it 9V or something close). 8 inputs to the transistors come from the micro-controller. So I can drive the large 7 segment (which require 9v) this way...

But it wasn't success. I checked the voltages and found the transistors switch between 0-5v (can't imagine how can this happen???).

Anyway, then I tried putting the resistor to the collectors side. And took the output from collector pin. That was *somewhat* ok. But the brightness was varying with the number of lighting segments...(When lighting only one segment, there was very little brightness. It's almost not visible. But when lighting all the segments, brightness was too high. Felt like the display will blow.)

I don't feel like to try other means. This was a so simple project. But this large seven segment ruins everything. Can some one help me with this...