On Sunday 15 June 2014 17:55:01 Gary Crowell did opine And Gene did reply: > I know that if one is getting false triggers on limit switches that the > first thing to do is check grounding and shielding, or debounce > settings. > > But I also see that it's recommended to go to a higher current and/or > voltage on the switches. > > So I've just laid out a little PCB that addresses this and some other > things. I'm wondering if it would have any general interest, and if > there are any suggestions for improvement. > > I did this, thinking about people who are using a simple controller, > like the HobbyCNC, where they might currently have switches > effectively wired directly to the parallel port, with just a 5V > pull-up. This, however is not an isolator; I figure that if someone > has an isolator it would already cover all the IO's. > > So what this is currently laid out to do: > > - 7 switch inputs, 14kV ESD protection on all. > - hardware debounce on all > - up to 18V on switches @15ma > - up to 4 switch inputs can be "OR'd" into a single output > - 7 outputs plus an OR output > - LED's for each output > - 5V 20ma drive on each output > - powered by a 20V wall wart or anything up to 40V. > > The ORing thing allows limit switches to be wired separately (rather > than in series), and combined logically into one output. FWIW, this > lets you see the action of each switch individually. > > Thoughts? > > Gary
Sounds good Gary, and I'd imagine some here might find it handy. But my BOB already has all the opto's, and tally leds. Its pullup/pulldowns (switchable) provide enough current I think to keep a cheap microswitch clean. And I am already a C.E.T., so that sort of circuitry is just a piece of perfboard away. :) Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ HPCC Systems Open Source Big Data Platform from LexisNexis Risk Solutions Find What Matters Most in Your Big Data with HPCC Systems Open Source. Fast. Scalable. Simple. Ideal for Dirty Data. Leverages Graph Analysis for Fast Processing & Easy Data Exploration http://p.sf.net/sfu/hpccsystems _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
