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[on:]

so i conect the positive of the battery  to one end of the reed switch and the other end to a led positive, negative of the led to a resistor and then to the battery negative...the reed switch closes and opens with a magnet as it SHOULD.

then i conect an arduino uno also, i put the magnet reed switch come ON,i remove the magnet and reed switch still ON it will not shut down the arduino...

do you know what might be wrong?

thi is the reed switchhttps://www.sparkfun.com/products/10601

it works with just the load of the led conected but with a bigger load it just stays on until i hit it with my finger lol

[Reply #1 on:]

If the switched current is too high a reed switch can sometimes weld shut.  The model you have it rated at switching 250 mA which should be plenty for the Arduino but perhaps there is a high "inrush current" due to capacitors.  How is everything wired?  What voltage is the battery?

[Reply #2 on:]

i have a 3.7 lipo battery

[Reply #3 on:]

I have seen situations where the reed switch itself becomes magnetized and insists on staying closed.  This mostly seems to occur when the switch is stored in close proximity with a strong magnet, or when the magnet is drawn (stroked) repeatedly along one terminal of the reed switch, magnetizing it.

I've also seen reed switches that have been held closed for long periods of time (several years) become magnetized as well.

A tape head demagnetizer touched to the switch and slowly pulled away while turned on usually fixed the problem.

[Reply #4 on:]

Draw us or tell us exactly how you have the reed switch wired to an arduino digital input pin. I suspect you have a 'floating input' condition and that there is nothing wrong with the switch. The easiest way to wire your switch is one side to ground, the other side to the input pin, and then enable the pin's internal pull-up resistor.

Lefty

[Reply #5 on:]

i am not putting the reed switch to a pin, i just want to power my board on and off. so far hitting it is the best way to turn it off lol

[Reply #6 on:]

i am not putting the reed switch to a pin, i just want to power my board on and off. so far hitting it is the best way to turn it off lol

You failed to answer my question, why? The switch has two terminals, what do these two terminals wire to? Don't spare the details, we don't charge by the word here. 

[Reply #7 on:]

one end is wired to the battery(-) negative therminal, the other terminal is wired to the arduino GND

[Reply #8 on:]

one end is wired to the battery(-) negative therminal, the other terminal is wired to the arduino GND

Well a ohm meter and a magnet should be able to tell you if the switch is FUBAR or not. The hammer is probably not all that useful a troubleshooting device, even though it can have therapeutic properties.