Re: how to safely stall a DC motor

Yes, as Les mentioned, the motor stays stalled. There are two
states of operations full speed forward for a tool change, and stop-

>reverse->stall for the rest of the time. It sounds like a terrible

way of doing things, and I can think of several mechanical ways to
due it much better, however, this is an existing proven design that
has been used for years and on several differnt models. At this
point I'm not interested in redesigning and rebuilding the entire
tool turret mechanism. I'm actually reverse engineering it and then
trying to mimic the original controls with my own as I'm installing
new controls for everything on this machine.

This is a special little motor that is not available anymore, so
making sure I can SAFELY stall it out for 99.5% of machine run time
is crucial as it will be hard to replace if I burn it out. By the
way, this isn't for a hobby, this machine will be used in a
production machine shop, so a run-time of 8+ hrs a day will be common.

I'm still looking into more elegant ways of controlling the motor
with H-bridge IC's etc... However, this level of electronics is way
beyond my current knowledge/experience level.

Comments/ideas are appreciated.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
> Lance Hopper wrote:
>
> > I'm in the process of completely retrofitting an Emco Turn 120
cnc
> >lathe. It's got an 8 position tool turret on a ratchet mechanism,
> >driven by a small DC gearmotor (24VDC ~15watts) through a worm
gear.
> > Would it be feasible to simply control the motor with a DPDT
relay
> >that supplies 24VDC for forward operation, and then supply 5VDC
and a
> >resistor of some value for reverse/stall operation?
> >
> > I'm not an electronics guru, so designing and building a
circuit
> >would be very time consuming and difficult for me. I'll be
> >controlling everything with Mach 2. Thanks for any advice.
> >
> >
> Yes, this should work fine. But, I think you need one more relay
to turn it
> off. It doesn't really keep the motor stalled ALL the time, does
it?
> Or, just
> long enough to get the tool firmly seated?
>
> Jon