Re: [CAD_CAM_EDM_DRO] Re: E-stop relay welds contacts for load dump resistor

> It sounds like the "crowbar and dissipate all current within 2 seconds" strategy is probably excessive

Unless you have a very heavy, very fast machine it should easily stop
within one second. Also the braking back EMF will keep the power supply
up longer if you are decelerating from a high speed.

Les

On 01/02/11 02:43, kzf817 wrote:
> I think that what Mariss had in mind with the circuit was a way to brake the servo motor to a stop when you have a runaway, such as when an encoder fails, or when you program some really long G00 rapid that is going to crash the cutter into something. I am really liking what you, and a couple of others have said about letting the bleed resistor be a very slow bleed (1k or something similar). So just do a slow discharge of the filter cap, to prevent it from staying charged forever when the machine is down, eliminating stored energy after a minute or so. I can always do an E-stop during a test rapid move, just to see how long it takes for things to stop. If it takes way too long, then I can re-examine things. It sounds like the "crowbar and dissipate all current within 2 seconds" strategy is probably excessive. Do any of you suspect that suddenly opening the contacts, without bleeding the cap, could cause damage to the Gecko's? If not, I will probably modify the circuit t
> o do a slow bleed. I have a few 750 ohm wirewound resistors left over from the original Bridgeport electronics, so this would be a perfect use for one of those. Having a 750 in front of the contacts would make life very easy for them. Thanks for all the help that all of you have been able to provide.
>
> Dan.