On Sunday 23 March 2014 15:05:18 Gene Heskett did opine: > On Saturday 22 March 2014 20:49:47 Cecil Thomas did opine: > > Gene, > > I also have a home brew encoder disk and interrupter set up on a 9x20 > > jet with a treadmill motor and an M60 controller. I also have a > > similar setup on a Monarch 10EE with a 3.5 hp 350 VDC drive motor. > > I was having a random problem cutting threads on both machines. The > > thread was losing its pickup occasionally and wiping the previous > > thread. This was an intermittent problem and it took a while to find > > the culprit. > > After watching a scope much more than I enjoyed I found that I was > > getting an occasional noise spike on the index interrupter which was > > of course the cause of the problem. > > My fix was to decouple the Vcc on every interrupter with a 1mf cap > > and I also snaked a length of "chinese fingercuff" braid over the > > outside of all the cables (grounded at the power supply end). I also > > ran a #6 bare copper from the motor frame to the control box chasis > > ground. I don't know if these attempts completely removed the noise > > spikes but I do know that I haven't wiped a thread since I did it. > > > > If I ever do another backfit I WILL use differential interrupters or > > packaged differential encoders. There is a lot of really nasty QRM > > associated with DC motors, DC motor controllers and relays. > > Thanks for the reply Cecil, but I've already been checking with a scope, > plus I'm using a C1G breakout with has a tally led in every I/O line. > The opto's I use are buffered, cmos output, and pull very hard to > whatever rail they should be switched to at the instant. So noise is > not a problem as even the ground rail is isolated from the lathe frame > in the way its mounted. > > When it happens, the lines involved simply go high & stay there. I'll > go get it off tomorrow, and open a drawer & lay a board on it for a > work table so I can sit and fiddle with my rework station, which has > tips down to 1/32" in diameter. When I carved it, the traces were only > like 7 or 8 mils wide, and its been patched to add small pots in series > with the leds so I can adjust the relative timing a bit. Because of > that, one could say its been hacked quite a bit from what I drew up in > eagle about 3 or 4 years ago. Throw in that the rat shack board i used > only has 1 oz copper on it, its trouble. 1 oz stuff is damned fragile. > Sort of like asking if concrete will crack. Wrong question, not if, > but when, because it will... ;-) > > When it did it to me this afternoon, I had already been on my feet > pushing my bad back for an hour too long, so that was the straw that > stopped me for the day. Getting old is not for wimps, and I'll be 80 > in October. But I'm not built to just sit in a rocker till I stop, > gotta be doing something. > > I'll find it, possibly related to it being a double sided board with no > plated thru holes, so it has to be soldered on both sides where a hole > is used to get to the other side. I may have missed at least one. > > Cheers, Gene
A good guess. I was using a resistor lead to get to the other side of the board, but when I added the led britness pots, wrestling one end of the resistor out of the board so I could run a wire over to the pot broke the copper foil on the other end, so when it warmed up a few degree, it broke the connection. Bitsy pieces of wrapping wire to the rescue, it was the ground buss. If I ever have to make another one, it will have at least 2oz copper on the blank board, this 1oz crap the shack sells is handy but darned fragile when your solder pad is only a 50 thou donut with a #61 drill hole. So now I have an almost cyclic 20 rpm wibble at 700 rpms that I think may be a beat frequency leak between the power lines 120hz in the controller, the the pwmgen.0.freq, and changing it up by 10hz seems to have made it much less obvious. I'll fine tune more when I get the mechanicals all back together. With this weather turning back into a wintry, blustery chill, with "snow showers" on the menu, it may be a day or 3. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/13534_NeoTech _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
