The cheap load cells often use a HX711 for the amplifier and A/D. See https://www.instructables.com/id/How-to-Interface-HX711-Balance-Module-With- Load-Ce/ if you're using an Arduino. If you want to roll your own interface code see https://www.mouser.com/ds/2/813/hx711_english-1022875.pdf
> -----Original Message----- > From: Gene Heskett [mailto:ghesk...@shentel.net] > Sent: Wednesday, April 17, 2019 10:01 AM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Something to think about re the hack-a-day tool > changer > > On Wednesday 17 April 2019 07:12:53 andy pugh wrote: > > > On Wed, 17 Apr 2019 at 06:57, Gene Heskett <ghesk...@shentel.net> > wrote: > > > Some more along the lines of finding out how much force I can figure > > > on as being available to tighten or loosen the collet nut. I can > > > get, for under a tenner, 4 ea 50Kg load cells and a processor board > > > that converts the very low level diffs of a wheatstone bridge > > > > Why not set your torque wrench to the correct torque for your nuts and > > then see how far down the handle you have to be to trip the wrench? > > > > That tells you what radius of action you need to get the right torque. > > > > There is no question that your machine can produce the torque, given > > the classical "sufficiently long lever" > > And that is the final question as to whether or not the idea is actually > practical. It assuredly is not if the xy motors are so weak it needs a > carousel more then 18" in radius to the circle of sockets just to > tighten a tool well enough to dig off .010" of an alu chip without > slippage of tool in the collet. Even that isn't going to be practical > but it does serve to outline exactly why the 3" radii carousels we are > seeing in the videos will turn out to be an obvious disproof of concept. > The videos of it going thru the motions on hackaday would certainly have > to suffer from the loose tools syndrome if actually put to work on a > usable thickness of alu stock, say .03125" thick. Putting bigger motors > on it would be one option, but even 470 oz nema 23's, might not be > enough, and most certainly could/would bend the frame or bearing rods. I > have the motors from the broken HF I can move, and probably will as that > would at least double the power, but just haven't found the round tuit > yet. Among other things they have dampers on them. But I'll have to > change the A motor again, putting a 435oz on it. I already changed the > 90 for a 230, so a 435 can't fail to be even better at holding work. > That would leave the pair of 235's for XY, and would leave the longer Y > to be moved to Z duties. > > The 1600oz nema 34 supplied as Z motor in the kit for a G0704, which was > a too slow disaster on the G0704, often stalling at 29 ipm, but was > strong enough to stretch the bolts anchoring the nut carrier to the z > sled, causing those to need replacement quite early, but now moves at 90 > ipm with a 940oz motor that has not further damaged those replacement > bolts, would be a prime example of overkill. However I reused that motor > as Z drive on the Sheldon, where it has no weight to lift, works well at > 75 ipm on the Sheldon with the same driver I took out of the G0704. I > put in the $180 AC powered drive to spin that 940oz on the GO704. Dead > smooth and 20 db quieter. The DM860H drive is a noisy drive, so noisy I > had to install miniature quarter round on the keyboard shelf edges to > keep stuff on it, including the keyboard and mouse. The 860 has very > very poor step vs amps in coils calibration, so there is no nice quiet > all steps in the microstep mapping regardless of the current setting. > The thing you notice most is that a /8 setting actually does 7 steps > because one of them is way too small. > > But thats not solving this measurement problem. Since this $7 kit, needs > an external clock, it seems like that could be done by siggen, for a 500 > baud baud rate, and a software uart could do the rest. But the packet > length is unk until I have such a kit in my hot little hands. The > fleabay adv's don't say. > > Thanks Andy. > > Cheers, Gene Heskett > -- > "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> > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
