Reed switches are
EXTREMELY reliable, I'd certainly much sooner use one of those than a hall effect device
Presumably he needs some kind of FET switch, and latching system - I presume it's for toggling a SCUBA light ON and OFF?.
Hello there,
Well i am basing my opinion on experience over about 20 years time, not some paper that the manufacturer wrote up. In that time i have seen maybe 10 reed switches fail for apparently no reason. The typical setting is they get stuck closed. I have been able to 'flick' them with my forefinger to get them to let loose and then they might work again for a while. I have never had a hall effect device go bad except for one where i applied too much pressure to the plastic case and then it did not work right after that, although it would still sense and provide an output.
A couple specific cases i remember well for reed switches:
I even got one bad that was never used. I ordered 6 units and 1 was stuck closed already.
I used one for a refrigerator sensor to sense the open door. The first one i used died in about a month. Current was about 10ma. the LED was a 5mm white Nichia type, with 3 AAA batteries to run when the door was open. The second one however lasted for more than 2 years now and is still going.
Some applications MUST use reed switches because they have to have low 'on' resistance or can not use any power when the device is 'off'. Offhand i can think of one which would be range switching. It would be much harder to use a HED for that.
So in short, i can only suspect that the quality of the reed switches come into question. Some are probably better than others. I've even seen plastic types and i stay away from those. Also as Tony said, the reliability is strongly related to the current.
PS. I have some really tiny ones, about 1/4 inch long (not including the leads)! I havent used them for anything yet though so i have no data to contribute yet.