Wish to reduce current draw on Hall sensor / Mosfet switch

Thread Starter

Kayakncycle

Joined Mar 19, 2020
3
Pieced together a waterproof switch; AH3572 Hall sensor to P channel Mosfet gate IRF 5210PBF. Seems to work, but draws 3mA in standby mode. Is there a way to simply reduce the amp draw while waiting for the switch to activate? Hoping to get below 1 mA.
Oops, both resistors in the circuit are 1 K ohms. Did not have necessary voltage at gate with 10K. Current draw collected from trusty $20 DMM.
Originally used resistor on source for hall sensor; could not make it work on the breadboard.
Switch for electric bilge pump in sea kayak: Hall sensor potted in epoxy glued to under side of deck. Magnet on top of deck slides right to left. Stopped by zip tie on bungee. Electrics in waterproof box inside rear dry compartment. 5 ft of 16 marine grade wire from switch to pump. To replace reed switch and relay.
Thank you
Dennis
 

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dl324

Joined Mar 30, 2015
10,536
Welcome to AAC!
Seems to work, but draws 3mA in standby mode. Is there a way to simply reduce the amp draw while waiting for the switch to activate? Hoping to get below 1 mA.
Not likely when the sensor itself can draw up to 4mA when it isn't driving anything.
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Thread Starter

Kayakncycle

Joined Mar 19, 2020
3
O-K, got it, thank you.
Checked Digi-key's product pages; found few with 2.7 supply current but reduced sensitivity. Think will keep what I got.
Learned to check an additional line of specs.
 

Wolframore

Joined Jan 21, 2019
1,743
What’s it for? Where’s the magnet? Reed switch draws no current unless it’s switched. Ok bilge pump, must be a float mechanism. Wonder if other ways to do this without drawing current.
 

Thread Starter

Kayakncycle

Joined Mar 19, 2020
3
Wolframore, sorry you missed it: "Switch for electric bilge pump in sea kayak: Hall sensor potted in epoxy glued to under side of deck. Magnet on top of deck slides right to left. Stopped by zip tie on bungee. Electrics in waterproof box inside rear dry compartment. 5 ft of 16 marine grade wire from switch to pump. To replace reed switch and relay.

I was getting 3 years out of a reed switch and relay. Also had flyback diode to protect switch. Sometimes would lose the relay, sometimes the reed sw. Trying to improve. This was my personal experience and I placed several electric bilge pumps in kayaks for friends. Strongly suggested they do maintenance work on the system regularly. 3 years was the low end failure rate when in salt water.

I want a mechanical snap switch I can operate with a magnet. The ones I jerryrigged myself were not robust and looked ugly.
 
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