3.3V and 5V Logic Argh!

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
divzr0
Posts: 8
Joined: Mon Nov 14, 2005 1:01 am
Location: Philadelphia
Contact:

3.3V and 5V Logic Argh!

Post by divzr0 » Sun Jan 28, 2007 3:08 pm

Hey guys, maybe a newbie question for some of you but I'm looking for some advice...


I'm using a TI DSP microcontroller that uses 3.3V logic and attempting to use the Parallax PING))) sensor. This particular sensor waits for a 10us high logic from the microcontroller and then takes a distance measurement and reports back a 5V high logic that translates into distance for the amount of time. The parallax sensor uses a single "Signal" pin....

I think I can get away with the microcontroller sending 3.3v but how do I get rectify the 5v down to 3.3 to the microcontoller and still preserve the singal pathway?

Any help?


Thanks!

User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Post by Chris Smith » Sun Jan 28, 2007 3:20 pm

A simple voltage divider will give you 3.3volts from the 5 volt signal.

divzr0
Posts: 8
Joined: Mon Nov 14, 2005 1:01 am
Location: Philadelphia
Contact:

Post by divzr0 » Sun Jan 28, 2007 4:52 pm

Chris thanks, but I don't think a voltage divider will work....

It works fine coming from the 5V singal of the sensor, but when the dsp microcontoller sends out, its logic is 3.3V so it would divide that further which I would not want.
Any other ideas?

User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Post by Chris Smith » Sun Jan 28, 2007 5:50 pm

You want to step it up?

Take the lower voltage signal and attach it to a base on a transistor that has a feed of X voltage, that way the smaller voltage gets bigger on the transistor out put side.

User avatar
philba
Posts: 2050
Joined: Tue Nov 30, 2004 1:01 am
Location: Seattle
Contact:

Post by philba » Sun Jan 28, 2007 7:15 pm

I'm not familiar with the chip you are using - does it have a bi-directional data line? There are translator designs for that using mosfets. there are also translator chips. here's a decent ap note - http://www.maxim-ic.com/appnotes.cfm/an_pk/1159

Post Reply

Who is online

Users browsing this forum: No registered users and 28 guests