- #1
Click For Summary
Discussion Overview
The discussion revolves around troubleshooting a homemade DC motor that is not functioning as expected. Participants explore various aspects of the motor's construction, including the type of magnets used, the electrical connections, and the rotor's movement.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant suggests that the strength of the ferrite magnets could be an issue and proposes using rare Earth magnets instead.
- Another participant emphasizes the need for more detailed information about the motor's construction and operation to provide effective help.
- A different participant raises several diagnostic questions regarding the rotor's movement and the effectiveness of the magnetic field, indicating that the rotor should spin freely and pull noticeably when energized.
- Concerns are raised about the potential for incorrect magnet positioning, which could lead to cancellation of the magnetic fields.
- One participant notes that the motor design does not necessarily require permanent magnets and suggests that steel could be used instead.
- Another participant mentions the importance of ensuring good electrical contact by removing the enamel from the rotor's wire.
- Some participants report that replacing the weak magnets with stronger rare Earth magnets resolved the issue, enhancing the motor's performance.
Areas of Agreement / Disagreement
Participants express a range of views regarding the potential causes of the motor's failure, with some agreeing on the importance of magnet strength while others emphasize the need for detailed diagnostics. The discussion remains unresolved in terms of a single definitive solution, as multiple factors could contribute to the motor's malfunction.
Contextual Notes
Participants mention various assumptions about the motor's design and construction that may not be fully detailed, such as the specific arrangement of magnets and the electrical connections. There is also a lack of consensus on the best approach to troubleshoot the motor effectively.
- #2
Borek
Mentor
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Please elaborate on the construction, please elaborate on what is happening when you try to switch it on, you can't expect people to know everything just by looking at one not-too-clear picture.
- #3
Adem
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Hey, could the magnet strength be a problem? I’m using ferrite magnets which are pretty weak
Could rare Earth magnets do the trick?
The connection seems to be fine with the coil / brushes / commutator and battery.
Could rare Earth magnets do the trick?
The connection seems to be fine with the coil / brushes / commutator and battery.
- #4
Borek
Mentor
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Everything can be a problem. If you will not give more details you will be just wasting time.
- #5
jrmichler
Mentor
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You need to observe what is happening, then describe it.
1) Does the rotor spin freely when you flip it with your finger? It needs to.
2) Does the rotor pull noticeably when energized? It needs to. The rotor poles need to pass close to the field pieces.
3) Your design does not need permanent magnets to work. A couple chunks of steel will work as well or better.
4) You have a high current, low voltage armature connected to a (relatively) high voltage low current power supply. See my point #2.
I built these type motors a long time ago. They spin really good when you adjust them properly and put enough current through them.
1) Does the rotor spin freely when you flip it with your finger? It needs to.
2) Does the rotor pull noticeably when energized? It needs to. The rotor poles need to pass close to the field pieces.
3) Your design does not need permanent magnets to work. A couple chunks of steel will work as well or better.
4) You have a high current, low voltage armature connected to a (relatively) high voltage low current power supply. See my point #2.
I built these type motors a long time ago. They spin really good when you adjust them properly and put enough current through them.
- #6
NascentOxygen
Staff Emeritus
Science Advisor
Homework Helper
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Hi Adem.Adem said:
Did you scrape or lightly sandpaper the enamel off the rotor's wire where the paperclip brushes need to make good contact? The varnish on the copper wire is an insulator.
The magnets need to be moved in closer, but I'm sure you have tried that
- #7
Adem
- 9
- 0
NascentOxygen said:Hi Adem.
Did you scrape or lightly sandpaper the enamel off the rotor's wire where the paperclip brushes need to make good contact? The varnish on the copper wire is an insulator.
The magnets need to be moved in closer, but I'm sure you have tried that
Yeah I’ve done both of them. I’ll change them with better magnets
- #8
Adem
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- 0
Also my motor is pretty much this motor just with a different battery and different magnets
- #9
NascentOxygen
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Is each tower of magnets holding itself together without glue? I think that means you have N-S poles together, so external fields are cancelling. Furthermore, you might have them positioned side on to the rotor, when they need to be end on. Check that. You might also have accidently reversed one of the blocks of magnets to how it needs to be. Best start with a single magnet on each side, get that working first.
You'll need the magnets stacked the way they don't want to stack, and then force them to stay together using sticky tape.
You'll need the magnets stacked the way they don't want to stack, and then force them to stay together using sticky tape.
- #10
Adem
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- 0
Found out the problem, magnets were too weak.
Replaced them with rare Earth magnets and it did the trick.
Replaced them with rare Earth magnets and it did the trick.
- #11
sophiecentaur
Science Advisor
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Put them closer together - right by the armature - and the motor will be much more powerful. That basic motor should work ok with simple magnets that were used in school labs.Adem said:
You will notice that all 'real' motors have an armature with iron in them. That concentrates the field marvellously and will give even more oomph.
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