On Saturday 15 March 2014 16:53:05 Peter C. Wallace did opine: > On Sat, 15 Mar 2014, Philipp Burch wrote: > > Date: Sat, 15 Mar 2014 20:45:18 +0100 > > From: Philipp Burch <p...@hb9etc.ch> > > Reply-To: "Enhanced Machine Controller (EMC)" > > > > <emc-users@lists.sourceforge.net> > > > > To: emc-users@lists.sourceforge.net > > Subject: Re: [Emc-users] I&$@)^ another C41 gone to hell. > > > > Hi Gene! > > > > On 03/14/2014 09:23 PM, Gene Heskett wrote: > >> Greetings again; > >> > >> After putting in a diode, that part seemed to work, but this C41 > >> seems to have gone south again. (and again (and again)), and its > >> looking like a 4th one has failed. Symptoms seem to be an output > >> impedance in the 100k region, making 375 rpm maximum, and dropping > >> nearly 100 rpm when I put a 10 megohm digital meter on its output to > >> measure it, and getting a hair over 5 volts for my trouble, and a > >> fresh LM358 in the output voltage follower stage acts exactly like > >> the one I pulled out thinking it was bad. > >> > >> So it looks like I need another, but it seems to me there ought to be > >> another choice besides this non-linear POS, and the PMDX-106. Or, do > >> I fire up eagle & design my own? > >> > >> The PMDX-106 works great, but its physically too big for the area it > >> needs to fit in by about an inch both ways. > >> > >> Anybody else got any suggestions? > >> > >> Thanks guys. > > > > Do you talk about this unit? > > > > http://cnc4pc.com/Tech_Docs/C41R2_USER_MANUAL.pdf > > > > I think it should be fairly easy to reverse-engineer the schematic of > > this little thingy, as there are only through-hole components and (as > > it looks like) just a single copper layer. > > > > But your comment about the LM358 in conjunction with the problem that > > you cannot go below ~200mV output voltage caught my attention: The > > LM358's output stage does not really sink current down to GND, so if > > the input of your following circuit does not have a pull down, it is > > likely that this amplifier is the cause of the problem. If so, you > > could simply replace it by a RRIO (rail-to-rail input and output) > > type, most standard opamps are pin compatible. If 16V max. Vcc are > > enough, the TLV2372 could be a suitable replacement. There should be > > many more to suit your needs, a quick parametric search yields at > > least three parts which should fit as well: > > > > http://www.ti.com/lsds/ti/amplifiers-linear/operational-amplifier-op-a > > mp-products.page#p78=In;Out&p1261max=32;36V;36&p480=2;2&p10max=0.02;10 > > 00000&p2954=PDIP > > > > Cheers, > > Philipp > > I can put the SPINX1 schematics up somewhere on Monday if it helps. Its > designed for FPGA PWM (at 5 KHz) so would need larger capacitors for 100 > Hz
That sounds like it would be interesting. My designs tend to be one function ponies and don't get to where they are "simplicated" well until about version 3 or 4. :) Thanks Peter. > It uses a THS4281 (the TLV237x series is nice but has a pretty high > output impedance so no better than ~.4V from rails with only about 2 ma > load) > > We get about 50 mv from the rails with a 10K load and better than 1% > linearity at 5 KHz (Linearity would be a lot better at 100 Hz) > > Design is Fast OPTO --> pullup --> 4000 series CMOS gate for precise > rail to rail PWM (OPTO is not) and CMOS has equal impedance both > directions --> 2 pole filter --> THS4281 follower Sounds like a fairly simple design, Peter. Thanks. The relay controls in the C41 work well, but I feel the spindle control is due for a serious rework. And despite the 4000 family being rated at 15 volts, I have run the decimal decoder on 28 volts for several years with only a modicum of detectable heat while it was switching at sub-microsecond speeds. I used it to put colored borders on the characters of a 1st generation NTSC character generator in 1980. FWIW, the input loading of the Gemini is just under 30k, or a fat 27k, so it really isn't that much of a load. Assuming 29k, its 53 microamps wide open by my calculator. Sending 15.5 volts into the Gemini's input. That is probably enough to make shrapnel out of that motors flywheel/fan. I think I would want some building walls and quite a few yards between me and it... I can't find it on your pages though. Is this available as a separate item? It sounds like exactly what I've had in mind. $$? $24, found it in the price list. Where is the web page propaganda? Found that too. Adapters and cables... Peter, I believe, if I can find an ENA signal pin I can use, this looks exactly like what I need. On the shelf? So taking an I/O inventory to find a pin I can use for the ENA is next. So far, 2 steps, 2 dirs=4outs, (X,Z) 3 spindle encoder ins=3ins, 2 braking outs=6outs, PWM and DIR outs=8outs, probe(used for home too with some hal trickery)=4ins. One input left I think. Unless in epp mode I can make it an out, and this is an atom D525MW board... Can that be done? Thats 8 outputs used already. Humm. Might have to build a one shot for the ENA in. if the port doesn't co-operate. I'm thinking, mostly thinking its about feedbag time. :) 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
