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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
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 |
#2
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
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. |
#3
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
Terry Pinnell wrote in message
news 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 |
#4
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
Terry Pinnell wrote: Have you looked at the brushes? Perhaps they're binding in the brush- holders, or getting to be too short. Mike |
#5
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
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 |
#6
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
"Terry Pinnell" wrote in message news 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. |
#7
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
"Bob Eld" wrote:
"Terry Pinnell" wrote in message news 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 |
#8
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
. 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? |
#9
Posted to sci.electronics.repair,sci.electronics.design
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Odd behaviour from battery motor
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. |
#10
Posted to sci.electronics.repair
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Odd behaviour from battery motor
In article ,
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 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. -- I won't see Google Groups replies because I must filter them as spam |
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