On Sun, 2010-12-12 at 18:08 +1100, Erik Christiansen wrote: ... snip > there is much greater risk of slightly > different input thresholds causing the outputs to contest, thereby > trying to short +5v to ground, when the input is slowly changing. > (Counted in nanoseconds) > > There is then a lot to be said for removing IC1C, so the slow input is > discriminated only once. If pins 1 & 3 are then connected, any small > same-chip threshold variation will have negligible effect, because here > the input flank is rather vertical.
Dooh, of course. I'll make the change. http://www.wallacecompany.com/machine_shop/EMC2/Charge%20Pump/chpmp-5c.png > > I need to add a voltage regulator and filter caps, but there is no magic > > there. I've noticed Matt's circuit is leaner because it doesn't need > > one. My circuit might be improved with some I/O protection, but that > > will make it more complex. > > For just one 74HC14, a resistor and 5.1v zener diode will do. I'm used to a Zener on a gate input to limit the input voltage, but the circuit input is an opto-isolator which is not so delicate. I noticed an "extra" diode on my Bandit drivers opto's. My guess is that the opto diode has a lower reverse break-down voltage and the additional diode shores it up? I'm concerned about the buffer output, which could have a pull-up, pull-down, and or current limit resistor. I suppose a Zener on the output could help with over-voltage or reverse voltage, but the buffer is supposed to be driving an input not a source, but an inductive load could be a source, but... I usually put off the output components until I know what I'm going to hook it up to. Though, this doesn't help in coming up with a more generic consumer grade product. > > I've ordered some 74HC14's in order to build my latest try, but I'm > > getting the itch to move on. > > A bigger ratio between C1 and C2 would make it easier to reject a single > input spike. But I can understand the attraction of seeing what the > laternatives can do. > > Erik The present C1/C2 ratio seemed to give the best compromise, but with adding the 74HC14 and probing the buffer output instead of C2 may change that. I'll order a range of caps to play with. Thanks again. I'll post the results of testing, but it may be a while. I hope I'll remember all this, I'd like to do a write-up for the wiki if it isn't already there. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Oracle to DB2 Conversion Guide: Learn learn about native support for PL/SQL, new data types, scalar functions, improved concurrency, built-in packages, OCI, SQL*Plus, data movement tools, best practices and more. http://p.sf.net/sfu/oracle-sfdev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
