Re: 10 amps to drive steppers

One of my customer's student disconnected a 4.6 amp stepper and it blew the
sense resistor and two mosfets.
Dan
-----Original Message-----
From: Tim Goldstein <timg@...>
To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
Date: Monday, June 14, 1999 9:51 PM
Subject: Re: [CAD_CAM_EDM_DRO] 10 amps to drive steppers

>From: "Tim Goldstein" <timg@...>
>
>Mo or Jon,
>
>Would love to have a schematic of this setup and would definitely be happy
>to get it posted.
>
>Regarding disconnecting a motor on a Camtronics board while it is powered
>and running, I inadvertently did this once and the board survived with no
>harmful side effects. I may have been lucky as I only had some small NEMA

23

>motors set up at about 1 amp.
>
>Tim
>[Denver, CO]
>
>> -----Original Message-----
>> From: Mo [mailto:mo@...]
>> Sent: Monday, June 14, 1999 7:50 PM
>> To: CAD_CAM_EDM_DRO@onelist.com
>> Subject: Re: [CAD_CAM_EDM_DRO] 10 amps to drive steppers
>>
>>
>> From: "Mo" <mo@...>
>>
>>
>> > From: Jon Elson <jmelson@...>
>> > A properly designed stepper driver shouldn't be troubled by operating
>> > with no load. Unplugging or plugging in the motor while the driver is
>> > active could cause some arcing that might cause damage, but just

running

>> > the driver with no motor connected shouldn't be a problem.
>>
>> Jon, unfortunately both types of board I have here warn that this is a
>> certainty
>> and I believe the Camtronics boards are the same. I have inadvertantly
>> killed one that way.
>> It must be in the design, as you say. Where a manufacurer warn
>> specifically
>> that their design
>> will be seriously damaged by this - it is good to take the precaution.
>>
>>
>>
>>
>>
>> > Here's what I did, although it is on a servo system, but the
>> problems are
>> > similar. The E-stop signal on my system releases a pair of relays (one
>> > a signal size, the other a power contactor). When these relays are
>> > released, they connect a power resistor to the servo amps power
>> > input, discharging the power supplies. When the relays are engaged,
>> > first the signal relay closes, connecting the same power resistor in
>> > series with the DC supply and the servo amps. Another contact on
>> > this relay connects power through to a time delay circuit. After
>> > a 1 second delay, giving time for the resistor to ramp up the
>> > voltage in the servo amps, the power contactor closes, delivering

direct

>> > power to the servo amps. When this relay closes, it also connects
>> > the enable input to the servo amps to +12, turning them on.
>> > This gets rid of all the high DV/DT transients when powering things
>> > up and down, and makes sure that whenever there is a fault, everything
>> > is powered down in a controlled manner.
>>
>> Perfect power up and enable sequencing. The power bleed resistors are the
>> absolute
>> minimum needed for those that do not have a similar set-up and
>> are still in
>> the process of playing around with their assembly.
>> Jon do you have a schematic for that set-up - if not I could
>> knock something
>> up and put it on Tim's site for members who would like to go that route.
>>
>>
>> Mo
>>
>>
>>
>>
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