On Thursday 27 December 2012 18:12:18 Kent A. Reed did opine: > On 12/27/2012 5:50 PM, Gene Heskett wrote: > > Greetings; > > > > I have now spent several hours doing google searches, looking for a > > chip that would be the reverse of a max232, so I can power this ttl > > based sparkfun thing from what is available from the serial port. > > There appear to be hundreds of variations on how to get from 5 or 3.3 > > volt powered motherboards to a serial ports voltages, but nothing to > > reverse that short of find an old ball mouse at a flea market and > > stealing the chip out of it. > > > > Unforch, I have attempted to look some of those chips up if they were > > marked, with zero luck. Most of that stuff was never a JEDEC > > registered chip design it seems. > > > > Am I going to need to invent what should be just another wheel? Any > > chance there is a ttl level serial port on a header someplace on the > > D525MW boards? > > > > Cheers, Gene > > Sorry, Gene, I've lost the bubble. What is the Sparkfun thingy you are > working with? I'm looking at their website but your description over the > last few messages don't get me to a specific product. > > Since the max232 is a bidirectional device, I would have thought it > would suit what I thought you are trying to do. So maybe I don't > understand what you are trying to do. > > Regards, > Kent It is bi-di, but its power sources are all universally either 3.3 or 5 volt. I need the reverse to work so I can power a ttl circuit from the nominal 24 volt swings offered by the serial port, using them as the supply.
The Sparkfun gizmo (ACS712 on their pages) is a hall effect driven ammeter, which I was going to broadband so as to be able to see, and trip, on the first excursion above 4 or 5 amps, tripping quicker than clearing a $.90 a copy 3.15 amp FB fuse. Or, do as I do on the mills motor, I have a 1.5 amp full scale ammeter on it, with a full wave bridge in series with the motor to make DC for the meter. The mill is about to stall the spindle when the current gets above about 1.25 amps. Sparkfun put an op-amp on the chip output to make it more sensitive, but for my purposes, it should have been a comparator. Minor detail but does complicate its use as an over current trip sensor. I did, when I built the driver box, dedicate 2 inputs for homing switches, but one got used for the spindle encoder, so I guess I'd better give up the other too and use it for this. Then I really am truly out of inputs as I am still considering a jig to drop on the ways and use G38.2 to zero each new tool I mount, so that G38.2 signal is not open for negotiation, it stays. That strikes me at this point as being more useful than homing switches on a lathe anyway. This I can probably rig up in the next day or so, dependent on the weather. The auto-zero jig will take a bit of carving on the mill, which is why I asked if anyone knew the included angle of the front way on the mini lathes bed one day last week. I presume no one knows for sure as no one replied. Thanks Kent, I'll get it sorted this way I believe. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! You have all eternity to be cautious in when you're dead. -- Lois Platford I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnmore_122712 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
