I am looking for a Hall sensor that is "0v" output normally but turns 5v when a magnet is close.
All of the hall sensor's that I have purchased are the other way around what should I be looking for? Any help would be appreciated.
Maybe a reed switch? It's a very simple and cheap digital sensor, I don't know if it's what you need...
A reed switch is to fragile for this project because it will be handled a lot!
The Hall Sensor right now constantly sends 3v to the digital pins on the arduino mega I have about 28 total sensors and was thinking that, that is a lot of voltage being wasted from my batteries! but if the sensor sent 0v and then if a magnet is close then send 5v that it would be more efficient.
chrisnet:
The Hall Sensor right now constantly sends 3v to the digital pins on the arduino mega I have about 28 total sensors and was thinking that, that is a lot of voltage being wasted from my batteries! but if the sensor sent 0v and then if a magnet is close then send 5v that it would be more efficient.
Maybe your thinking is wrong.
A switch with pull up resistor uses nothing when HIGH, and the resistor current when LOW.
Maybe your hall sensors work the same (active LOW).
Leo..
Hi,
Can you post some links to the Hall Effect devices you have considered?
Thanks.. Tom.. 
I found this as a reference TkkrLab
It say that the Power consumption, 3 mA in rest, 8 mA when switched on
If I had about 28 of these on one mega then at rest it would consume 84ma and there would be no more then 5 sensors on at one time which is 40ma for a total of no more then 109ma plus the mega
I guess this is not a big deal I am running this on a Lithium Ion Battery 3.7v 2000mAh
so at rest the battery should last about 20 hrs
I was just trying to find a more efficient way to run the sensors.
Here is the ons that I have right now.
Thanks
The module you linked to draws more current when active, because it has an onboard (10k?) pull up resistor.
The part itself (both other links) draws <=5mA, independent of output state.
Because they have an open collector/drain output (rely on external pull up).
So the part that is responsible for a higher draw when active is the pull up resistor.
That could be the internal pull up resistor of the Arduino pin (20-50k) if wiring is kept short.
Leo..
Wawa
Just so I am clear if I was to use just the hall sensor and use the internal pull up resistor of the "Arduino pin (20-50k)" then I could expect to see just a 5ma draw on rest or when switched on, is that correct?
When you say "if wiring is kept short" how short?
Thanks
chrisnet:
Just so I am clear if I was to use just the hall sensor and use the internal pull up resistor of the "Arduino pin (20-50k)" then I could expect to see just a 5ma draw on rest or when switched on, is that correct?When you say "if wiring is kept short" how short?
When the hall output is HIGH, you would just see the hall current draw.
And when the hall output is LOW, you would see the hall draw plus the draw of the internal pull up resistor.
That could be (5volt / 20k =) 2.5mA more.
How long is a piece of string.
It depends on what's nearby.
A capacitor (~10n) from pin to ground could help, and/or shielded wire.
Tell us what you plan to do.
Leo..
The sensor are no more then 6 inch's from the mega
This is just a game for the kids when they place a chip on a square spot on a board the mega responds
They pick a spot and the screen gives the feed back!
It is a little more involved then that! but that is the main idea.
thanks
chrisnet:
The sensor are no more then 6 inch's from the mega...
Then I don't see a problem with using the internal weak pull up.
Leo..