How to build your own external VFD / LCD
Howto by richbastard @ 2002-04-30
Howto by richbastard @ 2002-04-30
Connect your display:
I know there are other guides how to connect your display, but since we want it TOTALLY external, we have to make a few changes: we don"t connect our display on the 5V rail of our PSU, but we connect it to a USB port. Nice, clean & handy...
**disclaimer: USB ports can only handle 500mA. Check your display and make sure it doesn"t drain more power! If it does, it could fry your USB port. I will not be held responsible for that!**
My 4*20 VFD used in this article drains 275mA, so we can connect it to a USB port.
Ok, warm up your soldering iron and connect the wires acording to the following scheme:
LCD/VFD hole number |
Function |
Connect to: |
1 |
display: ground |
USB black wire (ground) |
2 |
display: 5V |
USB red wire (+5V) |
3 |
useless for us |
nothing |
4 |
RS (uh, dunno what this is for) |
Parallel pin 16 |
5 |
Read / write. Since we only use it
for writing => gound this |
Parallel pin 14 |
6 |
Enable strobe |
Parallel pin 1 |
7 |
Data Bus 0 |
Parallel pin 2 |
8 |
Data Bus 1 |
Parallel pin 3 |
9 |
Data Bus 2 |
Parallel pin 4 |
10 |
Data Bus 3 |
Parallel pin 5 |
11 |
Data Bus 4 |
Parallel pin 6 |
12 |
Data Bus 5 |
Parallel pin 7 |
13 |
Data Bus 6 |
Parallel pin 8 |
14 |
Data Bus 7 |
Parallel pin 9 |
15 |
backlight: +5v (displays without backlight,
like a VFD, don"t have this pin number) |
USB red wire (+5V) |
16 |
backlight: ground (same here) |
USB black wire (ground) |
master @ work ;^)
Notice the pin numbers go from 1 to 14, this is a VFD and therefore has no backlight (nr. 15-16). Thanks goes out to JMke who took this pics when I was assembling his 2*20 VFD!
The parrallel port connector. Be sure to use some shrink tube!


Cut the end of the USB cable and strip it. You"ll notice 4 wires. One of them is the ground (normally black) and one of them is +5V (normally red). I"d be a good idea to double check this with a multimeter. Attach the +5V of the display to the red wire, and the ground of the display to the black wire. Don"t forget to use some shrink tube.