On Tuesday, March 27, 2012 06:07:01 AM Erik Christiansen did opine: > On 27.03.12 01:46, gene heskett wrote: > > What do we normally assume to be the fwd drop of the usual LED, I > > assume IR, opto-isolated input? > > The good old 4N25 to 4N37 range is typically 1.18v at 10 mA, according > to the datasheet, so a bit less than the 1.6v we're used to from red > LEDs. (OK, I haven't measured one of those in 40 years, but that's still > what I expect too.) > > > Setting up stuff for the 2M542's target 10 ma thru its input opto's, I > > come up with about 360 ohms for the current limiter R when the 5 > > volts is 5.27, and the diode drop is nominally 1.6 volts. > > 390 ohms is closer, if your opto is similar. (But what's a mA here or > there.) > > > My old meter seems to have taken a hit, and my new one doesn't have > > the beans to measure a diode with more than about .85 volts for its > > band gap, so the diodes in the 2M542 are measuring either .75 volts > > if reverse biased, or open when conventional 'led' bias polarity is > > applied. To say I am a bit disappointed is an understatement, it is > > a $120 meter with all sorts of bells and whistles! > > Relying on some in-built measuring set-up is OK if it works. Isn't it > nearly as easy to wire up the 390 ohms, power up, then measure the > voltage drop in-circuit? (So long as polarity is right ... but we've > been there.)
Probably, but that will need a 6 position binder strip per motor super- glued in to hold the R's, which I haven't done yet. And I need to make a trip to the tv station & "borrow" another 25' of star quad mic cable for motor, encoder, and spindle controller wiring. 4, 22 gage conductors with an overall braid and foil shielding, it has worked well on the mill. I'll probably get that done today & tested if I can convince Arturo's C1G to come alive without a parport cable hooked to the pc since that hardware won't even ship till Thursday. > By the way, what's a 2M542? > > Erik The smallest of a fairly well regarded line of Chinese drivers, 50 volt, 4.2 amp stepper driver. It can microstep at 1/128 but I run them at 1/16 where the motors run noticeably quieter than at 1/8. It can be had for about a $50 bill a copy from several vendors on fleabay. I've bought 7 of them so far without any surprises. The mill has a 28 volt 9A supply in it for 4 of them, which is borderline low as its minimum is said to be 24 volts as they run hotter at the lower voltages. The mills version needs a fan blowing on the box for more than an hours duty at a time. This kit I'm building for the lathe will have about 39 volts under load. Not regulated, but well filtered. 40,000 uf in a pi section. I left it holding one motor (the Y motor at half current or 1 amp) all night last night as a smoke test & after the first hour, the 17 volt regulator (LM317- T) for the fans was the hottest thing in it at 113F on top of the epoxy-B. That salvaged si rubber insulator isn't a very good heat transmitter, the 1/4" alu plate its sitting on was only 77F in a 67F garage. With a PSU fan blowing on each drivers heat sink (2 fans, 2 drivers in this box) & with the lid & one side off, nothing else except the big transformers core was above 75F. So heatwise I may not need the external fan. This driver is also available at 80+ volt, 7 amp sizing. I ran across some servo drivers they make last night too, up to 320 volt, 20 amps but don't recall the pricing. They also sell under house brands, and appear to be the real supplier of the Kellig line of drivers. They even make one of the heavier stepper drivers with a builtin any voltage switching power supply. 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> The man who sets out to carry a cat by its tail learns something that will always be useful and which never will grow dim or doubtful. -- Mark Twain ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
