Author Topic: Contest of motor slowness, or lowness of voltage?  (Read 752 times)

Offline klugesmith

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Contest of motor slowness, or lowness of voltage?
« on: November 25, 2021, 05:50:35 PM »
Does anyone else think it's cool to see DC motors turning very slowly?
The linear relationship "speed = voltage * Kv" breaks down at very low voltage.
We need enough volts, on top of the back EMF, to push current and get torque
enough to overcome friction of bearings and brushes. 


First time I noticed was while making a project decades ago.  The small gearhead motor had armature shaft visible on one end. Found that it started and ran consistently at less than 1/10 of rated voltage. Armature turning at about 60 RPM.   

Cleaning up garage yesterday, I could not resist stopping to play with some motors in collection.
Posted a video (without narration; trimmed to 45 seconds) of one starting at 0.35 V and turning at about 100 RPM.
/>
Who want to beat that?   
« Last Edit: November 25, 2021, 05:54:24 PM by klugesmith »

Offline davekni

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Re: Contest of motor slowness, or lowness of voltage?
« Reply #1 on: November 25, 2021, 07:35:57 PM »
I have some very-similar looking DC motors w/o gears, that turn at similarly slow speeds.  They were for tape players.  Some have internal mechanical speed regulation by centrifugal-force actuated contact points.
David Knierim

Offline Mads Barnkob

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Re: Contest of motor slowness, or lowness of voltage?
« Reply #2 on: November 27, 2021, 07:52:59 AM »
I will have to look into my small-motors-from-stuff bin :)
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Re: Contest of motor slowness, or lowness of voltage?
« Reply #2 on: November 27, 2021, 07:52:59 AM »

 


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