The motor is on table with no capacitance to ground but then you mention capacitance I forgot the parasitic winding capacitance. The winding parasitic capacitance may actually cause a high differential current spike at switch turn on.
The disturbance travel from the COM pin to the signal GND on an IR2110 driver chip with an allowed voltage difference of a few volts so there are no real direction but the communication is still corrupted. I will try a simple resistor instead of motor, an ordinary high frequency inductor and common mode. I already tried a few turns with a ferrite. Nicklas Karlsson On Wed, 26 Nov 2014 12:12:16 -0800 (PST) "Peter C. Wallace" <[email protected]> wrote: > On Wed, 26 Nov 2014, Karlsson & Wang wrote: > > > Date: Wed, 26 Nov 2014 20:53:56 +0100 > > From: Karlsson & Wang <[email protected]> > > Reply-To: "Enhanced Machine Controller (EMC)" > > <[email protected]> > > To: "Enhanced Machine Controller (EMC)" <[email protected]> > > Subject: Re: [Emc-users] EMC communication problem then motor start > > > > The switching is very fast because gate transistor is 10 ohm so I will > > increase as an intermediate solution. The problem is however still > > interesting because it is so common. > > > > Nicklas Karlsson > > > > One option that helps a lot on PWM drives is a common mode choke on the PWM > outputs (a large ferrite bead on the 2 (DC) or 3 (AC) motor wires). One major > problem with PWM outputs without slew rate limiting driving motor windings is > the nearly unlimited current spike that happens at switching time because > of the very fast slew rate PWM signal driving into wiring/ motor winding to > ground capacitance. > > > > > > > > > > On Wed, 26 Nov 2014 19:34:44 +0000 > > David Armstrong <[email protected]> wrote: > > > >> i normaly make sure that all low voltage wiring is sheilded and watch for > >> ground loops and vfd inputs are via filters and Balance transformers , > >> ethernet coms are usually problem free so long as you use good cables and > >> not the cheap Aluminium wire ones as they are using balanced paired cores > >> , in 2 real major projects i ended up passing the low volt cables inside > >> sheilding cut from ur67 coax > >> > >> > >> > >> On 26 November 2014 at 18:40, Karlsson & Wang < > >> [email protected]> wrote: > >> > >>> I have tried with USB isolator made with Icoupler devices from analog > >>> devices on other products without luck. I am using ethernet which I think > >>> have a isolation transformer. I do not think there are any tolerances for > >>> missed packets right now. For serial communication I have tried opto > >>> couplers without with some improvement. I have also tried isolation > >>> devices > >>> from I think Texas instruments made from differential drive over two > >>> capacitors and they are great but I do not think I could use them for > >>> 100Mbit ethernet. > >>> > >>> I will increase tolerance for missed packets to be able to measure > >>> percentage of lost packets, it is not perfect but better than nothing. I > >>> will also add a common mode inductor and maybe a shielded cable. > >>> > >>> I have encountered the problem on several products so it is not isolated > >>> to just this one I built myself. > >>> > >>> > >>> Nicklas Karlsson > >>> > >>> > >>> > >>> > >>> On Wed, 26 Nov 2014 19:28:25 +0200 > >>> Marius Liebenberg <[email protected]> wrote: > >>> > >>>> I have had many problems with USB communications with motors and plasma. > >>>> You can overcome these by putting an electrically isolated barrier in > >>>> the usb line. There are some chips from Linear (LTM2448) that will do > >>>> just that. The equipment on either end cannot be connected to the same > >>>> ground or supply if you go this route. > >>>> > >>>> On 2014-11-26 19:07, Karlsson & Wang wrote: > >>>>> PWM is great for efficient motor but unfortunately it is also very > >>> good at disturbing digital communication. Do anybody had any problems with > >>> the communication errors then motor start? > >>>>> > >>>>> Nicklas Karlsson > >>>>> ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=157005751&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
