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Fire hazard with small DC motor jamming?

Madsalts

Sep 25, 2014
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I'm building an automatic fish feeder. First and foremost, I want to avoid starting a fire. Without knowing too much about electronics, it's my understanding that higher operating temps and higher voltage means higher fire risk.

I'm planning to have a small DC motor run off of a wallwart power supply. As the power supply is energized (via a timer), food is dispensed. Lack of energy means lack of dispensation. I'm going to use a 3V motor so as to keep the voltage low (do you think 6V would be just as safe?) Since this is for a fish feader (for an aquarium) I will seal things and secure things so that there is minimal chance of the assemply falling into the aquarium.

My main concern is that the feeder could (and probably will) jam so that the motor will be energized, but will not turn. I don't want such an event to generate excess heat and cause a fire. First, is this a concern with a 3V motor? Second, should I isolate the motor in a metal box? Should I take further precaution? This will be in use when I'm not at home.

edit: Another possible concern is dust generated from feed, though dispensation will involve low volumes (several grams).
Thanks.
 

Gryd3

Jun 25, 2014
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http://hackaday.com/2014/10/14/diy-auto-fish-feeder-feeds-fish-automatically/
Here is another project that you can relate to.

As far as a fire hazard is concerned. It's the 'power' that you need to worry about that causes heating.
A friend of mine had a 5V wire short out inside his laptop which caused the plastic case to melt and the LCD panel to discolor.
Keep the current down, and use a fuse to protect yourself.
 

Gryd3

Jun 25, 2014
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thanks. A fuse would not have occurred to me.
Remember they are one-shot... so if you size it too small or use a fast acting fuse, it may just pop when the motor starts.
It will need to be sized based on your motor, and will also help protect from shorts if the unit falls in the water. (Fuse should be placed closely to the power-supply/wall-wart)
 
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