Post by thread:[EE] Suggestion for 3.3V PIC to 5V device?

At 05:41 PM 6/6/2012, Marcel Duchamp wrote: >Looking for a 1-to-8 mux that will run from a 3.3V PIC32. It will be >driving servo signals. It looks like a '595 is just out of range to >reliably work. Umm . . . '595' to me is a shift register. If you need a 1:8 mux, I'm certain that a 4051 is rated from 3.0 to 15 Vdc. dwayne -- Dwayne Reid <spam_OUTdwaynerTakeThisOuTplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax http://www.trinity-electronics.com Custom Electronics Design and Manufacturing

On 6/6/2012 4:59 PM, Dwayne Reid wrote: > At 05:41 PM 6/6/2012, Marcel Duchamp wrote: >> Looking for a 1-to-8 mux that will run from a 3.3V PIC32. It will be >> driving servo signals. It looks like a '595 is just out of range to >> reliably work. > Umm . . . '595' to me is a shift register. If you need a 1:8 mux, > I'm certain that a 4051 is rated from 3.0 to 15 Vdc. > > dwayne > Thanks. Yeah, I just figured that one out, too. It's late..

Em 6/6/2012 20:41, Marcel Duchamp escreveu: > Looking for a 1-to-8 mux that will run from a 3.3V PIC32. It will be > driving servo signals. It looks like a '595 is just out of range to > reliably work. > > > Any suggestions? You are in the right path. You can use a 74HCT or 74AHCT device powered by 5V. Its inputs will understand the 3.3V CMOS outputs Fill a shift-register with zeros then walk a single '1' across all the outputs, waiting the necessary pulse width for each output. Repeat every 20ms. It takes just 2 I/Os, clock and data. The chain can have up to 10 outputs and yet ensure correct timing for all the servos (2ms x 10 = 20ms). Isaac

On Wed, June 6, 2012 8:10 pm, Isaac Marino Bavaresco wrote: > Em 6/6/2012 20:41, Marcel Duchamp escreveu: >> Looking for a 1-to-8 mux that will run from a 3.3V PIC32. It will be >> driving servo signals. It looks like a '595 is just out of range to >> reliably work. >> >> >> Any suggestions? > > > You are in the right path. You can use a 74HCT or 74AHCT device powered > by 5V. Its inputs will understand the 3.3V CMOS outputs > Fill a shift-register with zeros then walk a single '1' across all the > outputs, waiting the necessary pulse width for each output. Repeat every > 20ms. > It takes just 2 I/Os, clock and data. The chain can have up to 10 > outputs and yet ensure correct timing for all the servos (2ms x 10 = > 20ms). The PIC32 has 5V compatible pins- you can pull them up to 5V with an external resistor and run the I/Os as open drains. Not as fast as an active pull-up/pull-down, but definitely cheaper, and probably good enough for RC servos. Not all the pins are 5V compatible though, you have to double check on the data-sheet. Matt Bennett Just outside of Austin, TX 30.51,-97.91 The views I express are my own, not that of my employer, a large multinational corporation that you are familiar with

> > You are in the right path. You can use a 74HCT or 74AHCT device powered > by 5V. Its inputs will understand the 3.3V CMOS outputs I use the HCT trick all the time! Works great! Harold -- FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available! Not sent from an iPhone