Odd behaviour from battery motor

[Terry Pinnell]

I made my Curtain Controller 6 years ago based on a motor I stripped from an
inexpensive battery-operated screwdriver drill (3V). In general it has worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for such
a motor to exhibit this sort of behaviour and if so what's the likely cause
please? Is it fixable or am I going to have to find an identical motor?

--
Terry, East Grinstead, UK

 

[Sjouke Burry]

Terry Pinnell wrote:

I made my Curtain Controller 6 years ago based on a motor I stripped from an
inexpensive battery-operated screwdriver drill (3V). In general it has worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for such
a motor to exhibit this sort of behaviour and if so what's the likely cause
please? Is it fixable or am I going to have to find an identical motor?

--
Terry, East Grinstead, UK
Bad contact with the rotor commutator, a bad connection

in the field coils or the rotor coils, a bad on/off switch,
loose screws on the (internal) motor wiring ....etc....
Most probable the commutator contact, or an intermittent break in
one of the rotor coils.
Unless that last one is just on the commutator connection,
it wont be easy to repair.

 

[N_Cook]

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
newsr6eq5dq330c0j4q8vft3vtdfasp8njm7g@4ax.com...

I made my Curtain Controller 6 years ago based on a motor I stripped from
an
inexpensive battery-operated screwdriver drill (3V). In general it has
worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in
under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation
remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for
such
a motor to exhibit this sort of behaviour and if so what's the likely
cause
please? Is it fixable or am I going to have to find an identical motor?

--
Terry, East Grinstead, UK

I would settle for "if it ain't actually broke, don't poke", live with it
knowing that there is a break in the internal wiring and sometimes the motor
will run like a washing machine motor in wash cycle rather than spin cycle,
designed-in in that situation

 

[mike]

Terry Pinnell wrote:

Have you looked at the brushes? Perhaps they're binding in the brush-
holders, or getting to be
too short.

Mike

 

[Tim Wescott]

Terry Pinnell wrote:

I made my Curtain Controller 6 years ago based on a motor I stripped from an
inexpensive battery-operated screwdriver drill (3V). In general it has worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for such
a motor to exhibit this sort of behaviour and if so what's the likely cause
please? Is it fixable or am I going to have to find an identical motor?

When you were measuring voltages did you measure the voltage at the
motor, or upstream? You could have a bad connection between your
battery and your motor which would leave your battery as happy as a
clam, yet leave your motor under fed.

Have you checked for mechanical resistance? Perhaps the mechanism is at
fault, and the electronics are fine.

If the motor isn't seeing excess back-torque, and it's getting proper
voltage, then the problem is the motor. If not -- not.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

 

[Bob Eld]

"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
newsr6eq5dq330c0j4q8vft3vtdfasp8njm7g@4ax.com...

I made my Curtain Controller 6 years ago based on a motor I stripped from
an
inexpensive battery-operated screwdriver drill (3V). In general it has
worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in
under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation
remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for
such
a motor to exhibit this sort of behaviour and if so what's the likely
cause
please? Is it fixable or am I going to have to find an identical motor?

--
Terry, East Grinstead, UK

Bad brushes and or dirty commutator is the most likely cause. Clean or
replace the brushes. If possible chuck up the motor rotor in a lathe and
lightly sand the commutator exposing fresh metal, blow clean. A three volt
motor has almost no voltage "head room" to allow for loses in the
brush-commutator junction. Dirt and bad contact can cause the loss of half
of the drive which is what you apparently experience. A higher voltage motor
is much less prone to such failures.

 

[Terry Pinnell]

"Bob Eld" <nsmontassoc@yahoo.com> wrote:

"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
newsr6eq5dq330c0j4q8vft3vtdfasp8njm7g@4ax.com...
I made my Curtain Controller 6 years ago based on a motor I stripped from
an
inexpensive battery-operated screwdriver drill (3V). In general it has
worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in
under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation
remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for
such
a motor to exhibit this sort of behaviour and if so what's the likely
cause
please? Is it fixable or am I going to have to find an identical motor?

--
Terry, East Grinstead, UK

Bad brushes and or dirty commutator is the most likely cause. Clean or
replace the brushes. If possible chuck up the motor rotor in a lathe and
lightly sand the commutator exposing fresh metal, blow clean. A three volt
motor has almost no voltage "head room" to allow for loses in the
brush-commutator junction. Dirt and bad contact can cause the loss of half
of the drive which is what you apparently experience. A higher voltage motor
is much less prone to such failures.

Thanks all, much appreciated.

--
Terry, East Grinstead, UK

 

. I'm also sure it's not the mechanics,
friction, obstruction, etc.

How about the mechanics of the motor assembly?

Logically that seems to leave only the motor itself. Is it possible for such
a motor to exhibit this sort of behaviour and if so what's the likely cause
please? Is it fixable or am I going to have to find an identical motor?

Does the motor have gear pack reduction unit attached to it?

 

[Baron]

Terry Pinnell Inscribed thus:

I made my Curtain Controller 6 years ago based on a motor I stripped
from an inexpensive battery-operated screwdriver drill (3V). In
general it has worked fine. But for the last year or two it has
developed a strange intermittent fault. Suddenly, instead of opening
or closing the bedroom curtains in under 2 seconds, it will become
glacially slow, taking maybe 10 seconds or so. Although it always gets
there in the end (closing the appropriate microswitch), it's
irritating.

I don't mean 'intermittent' in the usual sense. It continues in this
slow mode for several *months*. Then, just as suddenly, it will revert
to its normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or
4th
time in 2 or 3 years. I made an even more concerted but fruitless
effort than before to isolate the cause. It's definitely *not* the
batteries, my primary suspect. I've tried several sets of 3 x
NiCd/NiMh C-types, well-charged, all giving identical results. Voltage
during operation remains more than adequate for the 3V motor. I'm also
sure it's not the mechanics, friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible
for such a motor to exhibit this sort of behaviour and if so what's
the likely cause please? Is it fixable or am I going to have to find
an identical motor?

--
Terry, East Grinstead, UK

Grease solidifying with age in the gearbox.

--
Best Regards:
Baron.

 

[Kevin McMurtrie]

In article <or6eq5dq330c0j4q8vft3vtdfasp8njm7g@4ax.com>,
Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote:

I made my Curtain Controller 6 years ago based on a motor I stripped from an
inexpensive battery-operated screwdriver drill (3V). In general it has worked
fine. But for the last year or two it has developed a strange intermittent
fault. Suddenly, instead of opening or closing the bedroom curtains in under
2 seconds, it will become glacially slow, taking maybe 10 seconds or so.
Although it always gets there in the end (closing the appropriate
microswitch), it's irritating.

I don't mean 'intermittent' in the usual sense. It continues in this slow
mode for several *months*. Then, just as suddenly, it will revert to its
normal fast mode. And stay that way for months.

A few days ago it once again reverted to slow mode, perhaps the 3rd or 4th
time in 2 or 3 years. I made an even more concerted but fruitless effort
than before to isolate the cause. It's definitely *not* the batteries, my
primary suspect. I've tried several sets of 3 x NiCd/NiMh C-types,
well-charged, all giving identical results. Voltage during operation remains
more than adequate for the 3V motor. I'm also sure it's not the mechanics,
friction, obstruction, etc.

Logically that seems to leave only the motor itself. Is it possible for such
a motor to exhibit this sort of behaviour and if so what's the likely cause
please? Is it fixable or am I going to have to find an identical motor?

--
Terry, East Grinstead, UK

I'd guess that it got oiled too much. Oil on the electrical contacts
acts as a speed regulator by only allowing the brushes and commutator to
touch through the film when they move very slowly. The thicker the oil,
the slower the motor. You can probably clean it with a Q-Tip through a
vent hole. Luckily it's a 3V motor. A higher voltage motor would
quickly arc itself to death doing this.
--
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