RE: [AVR-Chat] Timer Counter
2006-10-03 by Henry Carl Ott
At 07:41 AM 10/3/2006, you wrote: >I am trying to modifying a PIC program to get a shift register to work >properly, toggle the clear pin on the shift register to force all outputs to >"0" to prevent it from holding the data for too long and burning out an >expensive solenoid. > >The shift register is a 74HC595 and will occasionally lock an output on for >a long enough period to destroy a solenoid. I've seen circuits that will add a re-trigerable monostable multivibrator timer circuit between the mcu and the shift register. It acts like a missing pulse detector. If it does not see a clock transition every so often, it clears the /mr line. You can set the timeout window for every second or so, and make sure you update the shift register at least that often. I'm sure you could still have the mcu fail in some sort of loop that will still kill the solenoid, but this should really reduce that possibility Look at a CD14538b or 74hc123 datasheet for some ideas. carl -------------------------------------------------------- Henry Carl Ott N2RVQ carlott@si.rr.com http://users.rcn.com/carlott/ -------------------------------------------------------- Not everyone who offers you a rice dumpling is sincere.