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Re: Electromagnet Task

Posted: November 28th, 2017, 8:33 am
by ScottMaurer19
andrew lorino wrote:
dbli2000 wrote:When attempting to get the battery bonus, my electromagnet seems to suck away all the current as it is shorting the battery and the other circuits are barely recieving current. I have tried to add various resistors in an effort to prevent this, but then the electromagnet is too weak to throw the reed switch. Any ideas?
Maybe put it last, to mitigate its effects, or use a microcontroller or a bunch of transistors to make the reed switch's output turn off the electromagnet. This should be legal as you can extrapolate from the FAQ that said it was OK to switch a motor off later down the line.

EDIT: Or you could put it inline with some sort of circuit breaker, so that after a bit it would turn itself off, and use a thyristor to keep whatever the reed switch was powering on.
Wouldn't some sort of resistor reduce the current draw the electromagnet takes? As for the reed switch make sure the north to south pole axis is parallel to the reed switch.

Re: Electromagnet Task

Posted: December 20th, 2017, 2:50 pm
by karinaec2
How do we do the electromagnet without killing the battery? Ours keeps smoking/catching fire.

Re: Electromagnet Task

Posted: December 20th, 2017, 3:00 pm
by Unome
karinaec2 wrote:How do we do the electromagnet without killing the battery? Ours keeps smoking/catching fire.
Typically, overheating is caused by too high of a current - you may need more resistance in your circuit. I don't know enough about circuits or electromagnets to say for sure though.

Re: Electromagnet Task

Posted: December 20th, 2017, 7:11 pm
by davecutting
Please also make sure you are using insulated wire... :D

Re: Electromagnet Task

Posted: December 31st, 2017, 10:24 pm
by jinhusong
Measure the resistance of the EM. For 9V, it should be greater than 50ohm, other wise, add resister so total will be 50 or 100 ohm. Pay attention the resistor will be 1/2W or higher.

We used 32AWG magnet wire winding around 6-32 screw with power drill.

Re: Electromagnet Task

Posted: January 7th, 2018, 4:15 pm
by unknownuser2
Is it feasible to power the electromagnet with the water circuit?

Re: Electromagnet Task

Posted: January 8th, 2018, 4:05 pm
by dragonfruit35
unknownuser2 wrote:Is it feasible to power the electromagnet with the water circuit?
If you're referring to the task where you're completing a circuit via the addition of water to a container, then essentially yes. The water would act as a switch that allows electricity to flow to the electromagnet if you put it in series.

Re: Electromagnet Task

Posted: January 8th, 2018, 4:12 pm
by retired1
Plain water probably would not carry the amperage required for an electromagnet of medium size. Salt water would do a much better job.
Find a conductivity chart for various liquids.

Re: Electromagnet Task

Posted: January 8th, 2018, 5:13 pm
by PM2017
retired1 wrote:Plain water probably would not carry the amperage required for an electromagnet of medium size. Salt water would do a much better job.
Find a conductivity chart for various liquids.
Here's a link to such a chart.
https://sites.chem.colostate.edu/diverd ... utions.pdf

Re: Electromagnet Task

Posted: January 10th, 2018, 9:18 am
by dragonfruit35
retired1 wrote:Plain water probably would not carry the amperage required for an electromagnet of medium size. Salt water would do a much better job.
Find a conductivity chart for various liquids.
Oh yeah, sorry I didn't make that clear. I've tested with plain water and it doesn't work even to power an LED, you'll need to mix something in (note that you technically need to put whatever the other substance you're adding in the container the water will be added to rather than mixing it into the water itself because it's the addition of water that should complete the circuit).