View Full Version : 12v seven segment display

09-23-2008, 12:54 AM
I would like to know if·someone could help me with this.

I have a 7-segment display (actually 5) and they work with 12volts, but I want to controlled them with the basic stamp which only takes 5volts. Can you sugest any idea to do this?

Mike Green
09-23-2008, 01:36 AM
You need to post the datasheet for the displays you want to use as an attachment to your message. Go to the display manufacturer's website and search their website for the display model or part number. They will have some kind of datasheet with descriptions of the various pins, the signal voltages, the physical layout of the display, etc. There are all kinds of possible suggestions depending on the details of the display.

09-23-2008, 01:47 AM
Isn't it possible to use a Darlington Array chip as a 5 volt to 12 volt interface?

09-23-2008, 01:50 AM
Thank you Mike,
I attached the datasheet

09-23-2008, 01:52 AM
allanlane5, thanks for ur response. Do you know what chip is that one?

Mike Green
09-23-2008, 02:05 AM
You have a common anode display which is the easiest to handle. A ULN2803 is an 8 bit Darlington transistor array that is often used with a Stamp and can be used to control this display. There's a Nuts and Volts Column (#6) on using this and on using single transistors to switch larger currents and voltages than can be handled directly by a Stamp I/O pin.

Go to the main Parallax webpage and click on the Resources tab. You'll see a list of resources including Nuts and Volts Columns. Choose that and look through the index.

From the Resources tab, choose Downloads, then Stamps in Class Downloads. You'll see a list of tutorials. The one called Basic Analog and Digital has some chapters on expanding the I/O capability of a Stamp. You'll probably want to use a couple of 74HC595 shift registers to provide enough I/O to control 5 of these displays still using the ULN2803 to handle the voltage. Read the tutorial, you'll see.

Mike Green
09-23-2008, 02:12 AM
You'll need current limiting resistors in the segment leads. Their values will depend on the supply voltage for the LEDs and should limit the current to 20mA per segment.

09-23-2008, 02:14 AM
Thanks Mike, I REALLY appreciate your help!