Re: [CAD_CAM_EDM_DRO] Re: how to safely stall a DC motor

Although stalling a motor sounds horrific it really isn't a problem.
Let's assume the motor has 2V across it and the resistor limits the
current to 0.25A. The power dissipation in the windings is 2*0.25 =
0.5W. This is negligible. I retrofitted one turret and made another from
scratch, both using this principle. They often get left running for days
at a time with no problems. The motors only get very slightly warm.

Les


Lance Hopper wrote:

> 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.
>
>
>

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