This is what the above circuit is supposed to accomplish: As long as a magnet is held above the hall sensor, it will turn on the coil. It does that by utilizing a power transistor.
Will this setup work properly? Will it work properly if up to ten of these circuits are connected to eachother and how much battery power would I need to run it?
--- I won't run properly unless you connect the coil between the collector of the transistor and battery + and connect a diode across the coil with the cathode of the diode going to battery + and connect the emitter of the transistor to battery -. It also won't work properly if you don't have enough current coming out of the Hall sensor, and you may toast the transistor if you don't put a resistor between the output of the Hall sensor and the base of the transistor.
As for the rest of it, until you can more clearly describe what the parts look like, electrically, and what you really want to do, you're just pissing in the wind.
-- John Fields
Hi, Paladin. There are many types of Hall Effect sensors, and you're not too specific about which one you're using, so I can't say for sure. However...
Many hall effect sensors are made with "open collector" output. That means that, when they're on, their output pin will sink a few mA of current from a pullup resistor or other source.
If you've got a type like that, you might want to try using a PNP transistor and try something like this (view in fixed font or M$ Notepad):
.----------o--------------o----. | | | | | | | | | | | | | | .-. | | .----o---. R| | | | | + | | | | | | | '-' | | | Hall | ___ | |< | | Effect o----|___|-o--| --- | Sensor | R |\ - | | | | | | .---o | | - | | | | '----o---' | | | | | C| | | - C| | | ^ C| | | | | '----------o---------------o---' created by Andy´s ASCII-Circuit v1.24.140803 Beta
Choose R such that about 1/10th of the current required by the relay coil will be drawn by the base (note that many of these hall effect sensors are limited to about -20 mA output current, so keep that in mind).
I hope this works for you. Be sure to check your sensor to check the specs. If you're not sure, feel free to post again with more information. Battery voltage, relay coil resistance, sensor type would all be helpful.
Good luck Chris
"It's all coming back to me now", said the blind man as he peed into the wind..
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