Re: DC Motor Control: H-Bridge +5A, 48v

In article <lfd281hl7ib4d2b07t7q3nt7kk5n5hl9eu@xxxxxxx>,
cdsmith69NOSPAM@xxxxxxxxxxxxx says...
> On Tue, 10 May 2005 13:08:49 -0400, R Adsett
> <radsett@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> >I once did the SW for a variant that used a pair of controllers to
> >control a series wound traction motor in an H-bridge configuration. We
> >had the current oscillating at about +-700A IIRC with the motor reversing
> >direction every few seconds. I could swear I could feel the magnetic
> >field off of that sucker. Twitching 00 cable does make for an intriguing
> >sight.
>
> That reminds me of another thing. Way back when I started at the
> forklift company in 1994, the engineering department was a bit
> lacking in equipment. So for a while, we had to use an old WYSE
> terminal for debugging. The forklift had a serial port on the
> controller board and you could plug in a terminal or computer
> with terminal program, and look at things like all the sensor
> readings, examine memory contents, etc.
>
> When we would run the lift motor at about half PWM, which
> resulted in maybe 250 amps or so, the image on the CRT of that
> old WYSE terminal would shake up and down about 1/4 inch, even
> though it was on a table a couple feet away.

Seen that too. It sounds like we had similar experiences at roughly the
same time. Any chance your lift truck was a reach? :)

Speaking of current limits. The controller was designed, over my
objections, to use the NMI to signal an over-current. The hardware would
cut out the PWM for one cycle and leave it up to the SW to correct the
problem more permanently. Under the right circumstances, which of course
were not too hard to produce, you would get a cascade of NMIs as the SW
tried to react to one NMI and failed to do so before the next occurred.
The end result was either a small hesitation which was not really
noticable unless you were looking for it, or overloading the processor so
much that it either blew the stack or triggered the watchdog resetting
the controller in the process or worst of all loading the processor down
such that it was effectively stuck for a short period of time. I managed
to eliminate the last in SW. The board was eventually redesigned to put a
one-shot on the NMI. Ugly, but workable.

Robert
.

Relevant Pages

  • Re: Student Question on using a PID as a Dimmer to Control a Light Bulb!!! This is a fun one!!!!!!
    ... I have a few questions the PWM signal sounds like it may burn out most ... you mentioned a variable voltage method. ... temperature controller -- this is where my knowledge and experience ... by an electrode called the gate, separated from channel by a thin layer ...
    (sci.engr.control)
  • Re: Power Supply keep blowing
    ... Unnecessary since the PWM works just fine on the ... high side without another expensive transformer. ... However some bought supplies that sold on price; ... the need for isolation is eliminated if the PWM controller is on ...
    (alt.comp.hardware.pc-homebuilt)
  • Re: PWM control
    ... I need a PWM controller to set the ... manual control that I can set for intensity. ... Because the laser is so old Synrad no longer has any info on it. ... Synrad did say it was controlled by a PWM signal. ...
    (sci.electronics.design)
  • Re: Buck converter, controller riding on the switch node
    ... a typical buck converter with current mode control has a PWM ... controller referenced to output ground, a current sense transformer to ...
    (sci.electronics.design)
  • Re: DC Motor Control: H-Bridge +5A, 48v
    ... The controller was designed, over my ... overcurrent was tripping. ... the next PWM cycle after the one-shot. ... Later we were designing a new controller that did cycle by cycle ...
    (sci.electronics.design)
Loading