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| Solid state "high current" magnetic switch? |
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| rea5245:
Hi, I want to turn a microcontroller-based circuit on and off based on the location of a magnet. My first thought was to use a reed switch, with Vcc coming through the reed. But then I thought, maybe there's a solid state or MEMS alternative. I looked around and found only magnetic sensors, which don't provide the "high current" (not really very high - just 100mA or so) that powering a uC would require. It seems the magnetic sensors are just intended to provide a signal to an IO pin. Is there something smaller and less fragile than a reed switch that can turn power on and off? And what I really want is for the switch to be open in the presence of a magnet, and closed when the magnet goes away. Thanks, Bob |
| filssavi:
The only solid state alternative I know is a latching circuit (soft power on) with a Hall effect digital sensor as trigger |
| jbb:
Two options come to mind: * a Hall Effect sensor and a load switch IC such as the AP2280 * using a deep sleep mode in the microprocessor (some have a 'shutdown' mode with < 1uA draw) and connecting a Hall Effect sensor to the wakeup pin I would tend to suggest the microprocessor sleep mode because it's smaller and cheaper. Also, you would be able to leave the micro on for a brief period to finish off a task after the magnet is removed. Finally - look out on the Hall Effect sensor. Do you want it to respond to North poles, South poles or either pole of a magnet? |
| T3sl4co1l:
Note that Hall effect sensors can be costly in terms of operating current. It may be worthwhile to run the micro periodically (sleeping most of the time) and poll for inputs, turning on the sensor to check. The sensor may take a long time to start up or settle. Check if the datasheet says anything about it, and check around for other parts if they're any better or what. Reed relays aren't terrifically cheap but they are dumb, stand-alone components. :) Tim |
| calexanian:
Yes a reed switch to drive a relay coil. |
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