On Thu, Sep 8, 2022 at 7:04 PM gene heskett <ghesk...@shentel.net> wrote:
> On 9/8/22 18:03, Chris Albertson wrote: > > I did not know about these. Thanks so much for posting. So, after the > > software stops cycling the output pins, the 10 uf cap discharges through > > 750 Ohm the opto-isolator's LED and the relay opens. I will have to > > calculate the time delay, but my back of the envelope says about 0.02 > > seconds. Is that close to what you observe? Or did I miss a decimal > place? > > > > It looks like you have a good design and if you can sell these at a > > reasonable price they should be standard equipment. > > > > But I was thinking, Now that we have companies like JLCPCB who can make > > printed circuit boards and solder components for well under $1 per PCB, I > > would not want to be in the business of making and selling small > electronic > > devices. I would design this thing so that it used only parts from > > JLCPCB's "short list" to keep the cost under $1. Post the design files > and > > let people order their own directly from the manufacturer. > > An interesting idea. Any idea of the delay to expect after they receive > the order and the > payment? > 24 hours from design file to finished product. Plus shipping time from China. You can pay for overnight shipping from China or cheaper for slower shipping. There is zero setup fee if you use parts from their "short list" of a few thousand parts, as these few thousand are always loaded on the pick and place machine. For a flat $2 you get five boards, 2 or 4 layers, each up to 100mm square. Bulk pricing is $56 per square meter. Basically the current cost of small PCBs is so close to zero that it may as well be free. https://jlcpcb.com/ They do charge extra for the parts but only the cost of the part. Most passive parts like resisters are fraction of a penny, perhaps $0.002 each. A microcontroller might cost a few dollars and a 10 uf electrolytic cap 3 to 10 cents. PCBs are so cheap I used them for stupid purposes like a PCB with only connectors just to route signals and avoid "rat's nest" You don't need an EE degree to make a PCB with no parts. Here is one I made just to conectorize a breakout board. This is like a "hat" but it goes under the tiny computer board. The part I had them make is the green board in this photo https://github.com/chrisalbertson/NeatoLidarInterfacePCB I paid $2 for five copies So if you wanted one of these (you don't, they are obsolete) you would download my Github project and then drag and drop the design files to the web site linked above. Shipping is not cheap. DHL does not give discounts just because the content of the package is only $2 so it pays to wait until you need a bunch of different PCBs as they charge per package. The PCB indstry has a "standard" file format, like g-code. They call it "Gerber files" the best free software is KiCAD. The "photo" in the above link is actually a render made by KiCAD before the part was manufactured. It is easy to do really basic stuff like this. My idea for a "perfect" LCNC setup is to design a "motherboard" and then plug in all the other parts. There would be no wires The quality is first rate as this is a top tier manufacture. They process 20,000 orders per day, so a minimum of 100,000 PCBs per day. Obviously not a garage shop operation. The catch? You had best use parts from this list or the cast and time goes way up. https://jlcpcb.com/parts > My concern with this is that it does not catch a failure where only the > > user space program crashes and the kernel-space task continues to run. > > Perhaps something else can watch for this? > > I have not ever observed that. Not saying it cannot happen, but based > on my experience, > someplace between pretty slim and point triple ought zip. > It would be rare on tested and released code. but I'd thinking of using this on robotics code I wrote when testing it for the first time. It will almost certainly fail. I've burned up motors commanding them past limits then crashing. > > > > > On Thu, Sep 8, 2022 at 2:15 PM <m...@mattshaver.com> wrote: > > > >> On 2022-09-08 15:55, andy pugh wrote: > >>> I rely on the Mesa watchdog. If I was running a system that couldn't > >>> do that then I would start looking t watchdog circuits, though last > >>> time I looked I didn't see anything that simply opened a relay if the > >>> charge pump stopped. > >> I actually make this: > >> > >> http://www.mattshaver.com/site.php?link=pcbs/cp2estop/index.htm > >> > >> It was used in Smithy machines and I have a bunch of them left. Haven't > >> sold one in years and don't know what they should cost anymore, but if > >> someone needs one I could look into it! :) > >> > >> Thanks, > >> Matt > >> > >> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > > > > > 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, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/> > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
