Yes, my error. Had the picture in mind, but the text came out wrong. What about this;
http://www.fotothing.com/photos/1f5/1f5ff1cf0801bfc786bfbb8663578306.jpg A few points; by default, the motor is shorted out unless the relay is active only require one SPDT the amp never see's no load the motor is always 'connected' the zeners protect the drive and not the motor the resistor in line with the motor is quite high, maybe 470ohm and is to prevent arcing the balance between the two resistors is such that the amp still sees a load, but won't be able to drive the motor. But I'm sure this has been attended to ad-infinitum in industry. Just gotta find the popular configuration. Regards Roland On 10 April 2010 10:42, Erik Christiansen <dva...@internode.on.net> wrote: > On Fri, Apr 09, 2010 at 02:17:28PM +0200, Roland Jollivet wrote: > > A DPST will perform the function fine, unless you want DPDT for some > other > > reason. > > Hmmm, maybe you meant to type SPDT? Even leaving one side of the motor > connected to the H-bridge output, we have to switch the other side of > the motor away from the H-bridge to a shunt resistor. I've collected > components, and am starting to build that up. (The relays to hand are > only SPDT, after all.) > > Now, should I connect a pair of back-to-back hefty zeners or transorbs > across the motor, to clip the hundreds of volts of back-EMF which could > be generated by interrupting 10A flowing in the motor winding? The shunt > resistor is not in circuit until the relay armature completes its > travel. That could be enough to let the magic smoke out of the 7i40's > H-bridge FETs, unless there's very robust protection there. > > Alternatively, using Andy's bridge rectifier idea reduces the number of > great fat zeners required. I then just have to add one common > overvoltage shunt across the supply rail, close to the four > motor-stopping relays. > > Thanks for the suggestions. (I'd hate to blow up a 7i40 by guessing > wrongly while trying to increase protection against mishaps.) > > Erik > > -- > In all affairs it's a healthy thing now and then to hang a question > mark on the things you have long taken for granted. > -- Bertrand Russell > > > > ------------------------------------------------------------------------------ > Download Intel® Parallel Studio Eval > Try the new software tools for yourself. Speed compiling, find bugs > proactively, and fine-tune applications for parallel performance. > See why Intel Parallel Studio got high marks during beta. > http://p.sf.net/sfu/intel-sw-dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
