On Friday 21 February 2020 11:53:16 Nicklas Karlsson wrote: > > Greetings all; > > > > I have added a 40 amp SSR in the relay box with the two that are > > sequencing the spindle's psu startup for a soft start, but its not > > intentionally connected to those 2 other than as a power src when > > its enabled. Except this one is to be enabled by the E-stop.out > > signal when its on, f1 pushed once after start. The idea is to turn > > on motor power etc to the remainder of the system with the F1 key. > > Be aware that failure mode of SSR I am pretty sure is short ciruit so > that it does not turn off. Expect SSR is implemented with a thyristor > or mayb triac and they will not turn off a load with low power factor. > Even though it is very likely to work most of the time I would not > fully trust a F1 button for emergency stop.
I'm aware of that, but so far I have had zero failures with the hoymk brand of 40 amp 450 volt SSR's from mpja.com since using 2 of them to soft-start the spindle motor psu for about 3 or 4 years now. 2 of them are controlling all motor power including a 1.5 horse vfd from a pi running the sheldon. So when lcnc isn't running, the Sheldon draws less that 10 watts, and its monitor draws 11 watts. > I would consider these two above as a problem if you need some safe > way to turn of machine then for example changing tool or climbing into > the machine for some reason or for some reason need to touch a part > that might cut fingers. Machine is a small grizzly g0704, a 400 lb tabletopper on a stand, and the only time it would be called upon to interrupt the full load would be an estop situation. Its worst starting load would be the two switchers for xy, and the line powered z combined driver unit. The spindle power only comes on after this is on, and the normal shut down kills that first by inserting that 200 watt 51 ohm R back into the circuit a few hundred ms before a total shutdown. And theres a wall switch between the machine and its computer that kills the computer and interface if thats needed. It will see the machines full load amps at E-stop shutdown. So it will get tested heavily. Its actual switch is in series with a switch/breaker in a multiplug strip screwed to the box that I have been using to shut off everything but the computer and interface. All I'm doing is makeing it shut off its own motor power completely when the job is done. I'll remap the an m2 into an m2.1 to do that. While I'd much rather have a big t-bar contactor, have you priced those lately, not to mention you need boosters to handle the coil currents they need. These are $11 a copy and a sub 10 mill logic signal from a bob can control them. Simplicates things nicely. Thanks Nick. 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
