I've come here again for advice. My basic project now requires a resettable fuse or breaker, and a polyswitch will work from what I gather. However, I'm confused how they rate the things. I can understand the hold current, but they rate them with trip current X amps (i.e. 30A), then rate the trip time at a much higher current (20sec @ 75A). Could this cause a safety issue running 14awg wire? Will it ever trip if the motor is used 1/2 second at a time?? The motor I'm using has a 15A fuse in it's original application, which leads to another confusing issue - how it can blow 30A fuses.
My project uses a automotive wiper motor (high-torque gearhead) to pull a cable, which opens an exhaust cutout. It only has to move that cable ~1" back and forth, which is roughly 20 degrees of shaft movement, but several rpm's. The car it's from uses a 15A fuse, but in my application it can sometimes meld a 30A fuse! I think because it is cycled closed/open when I shift gears, and because it's rubber stoppers are fairly stiff, its a bad mix of inrush current, stalling, and fuse over-heating causing my problems. I have the diagram on paper, but all it really does is use a DPDT relay to reverse the polarity to the motor, with limit switches to kill either 'throw' of the relay. FYI they are set to limit before the bumpstops, since the inertia carries them well enough.
All I could really find is the following thread, which kinda confirmed my suspsicious why its pulling so much current.
http://forum.allaboutcircuits.com/showthread.php?t=6802&highlight=polyswitch
Here are 2 short vids of my project in action:
http://www.youtube.com/watch?v=1_2RlSZoplw
http://www.youtube.com/watch?v=Cz27DVw7HD0
My project uses a automotive wiper motor (high-torque gearhead) to pull a cable, which opens an exhaust cutout. It only has to move that cable ~1" back and forth, which is roughly 20 degrees of shaft movement, but several rpm's. The car it's from uses a 15A fuse, but in my application it can sometimes meld a 30A fuse! I think because it is cycled closed/open when I shift gears, and because it's rubber stoppers are fairly stiff, its a bad mix of inrush current, stalling, and fuse over-heating causing my problems. I have the diagram on paper, but all it really does is use a DPDT relay to reverse the polarity to the motor, with limit switches to kill either 'throw' of the relay. FYI they are set to limit before the bumpstops, since the inertia carries them well enough.
All I could really find is the following thread, which kinda confirmed my suspsicious why its pulling so much current.
http://forum.allaboutcircuits.com/showthread.php?t=6802&highlight=polyswitch
Here are 2 short vids of my project in action:
http://www.youtube.com/watch?v=1_2RlSZoplw
http://www.youtube.com/watch?v=Cz27DVw7HD0