Hall Sensor on/off switch without an arduino

Projects General Guidance
1

Hi all,

I have a project in mind, where you could turn LEDs on and off by moving a magnet close to the thingie. When it's on, touching the box with a magnet would turn the LEDs off, and on again with a second touch.

I'm pretty confident with programming, but not so much with electronics.
Looks to me that building a circuit for this with an arduino is quite straightforward.

Now, without an arduino, if I got it right, I'd have to build a flip-flop circuit. Looking at this website, it can get pretty involved. Almost daunting.

These are my pros and cons for each approach:

  • Price: without an arduino it would be cheaper, since I want to build a few of theses
  • Complexity: with an arduino I don't have any worries. But without one might be over my skill level
  • Size: The complete thing should be as small as possible (say under 5cm). It's kinda clear how small arduino boards get, so actually it feels like the flip-flop piece would take up more space (Compared to Flora)
  • Power: Because of the size limit, there's not too much space for batteries. An arduino would definitely would require more juice.
  • Parts: Without an arduino, I'd need a lot of different components I don't have at the moment.

This is just a list of educated guesses, so I'd love to hear your input, on which way to go.

2

This hall sensor , a battery, a resistor and an LED are all you need for simple switch. For more complicated behavior, consider programming an 8 pin ATtiny (doable with Arduino). No other external parts would be needed, and the ATtiny chip will be about the same size as a flip flop.

3

Have a look at reed switches. It may have enough throughput to turn on the led.

4

Hold on, hold on!

This is what I want to build:
LED is off. I tap the box with the magnet, hide the magnet to never be seen again, yet LED turns on, and stays on.
LED is on. I tap the box with (an other) magnet, mail the magnet to back to the store, and the LED turns off, and stays off.

So I don't think either suggestion would work without some extra stuff.

5

When you say "the magnet" and "another magnet" are you implying some kind of encoding?- recognition of magnet A not being the same one as magnet B, or just any magnet will work?

6

JimboZA:
When you say "the magnet" and "another magnet" are you implying some kind of encoding?

Not at all. (Good idea, though)
Just wanted to emphasize, you'd tap then remove the magnet. I.e. the Hall sensor should work just as push button.

7

A standard hall effect will just turn on and off as a magnet is presented and removed.
It will not stay on.

There is a "latching" type hall effect switch though.

It turns on, if I remember correctly, with a south magnet and off by either reversing the same magnet to north or by using a seperate north magnet.

I used them once in an experimental ignition system.

Check the link here.

http://www.allegromicro.com/en/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Latching-Switch-Hall-Effect-IC-Basics.aspx

8

by using a seperate north magnet.

All magnets examined to date have both a south and a north pole, although the possibility of a magnetic monopole has not been excluded!

9

jremington:
All magnets examined to date have both a south and a north pole, although the possibility of a magnetic monopole has not been excluded!

That was not what I meant ..........ok then how does "a seperate north face" sound to you..?? :wink:

10

bluejets:
A standard hall effect will just turn on and off as a magnet is presented and removed.
It will not stay on.

Yep, that's why I said that it would simply act as a push button.

Thanks for the link about latching sensors. That's actually a good idea, and @jremington's original suggestion makes a lot more sense now.

But let's stick with the original plan. Why? The target audience is less then 1 year old, and I'm not sure that all this turning the "magic wand" this way or the other would make too much sense for him just yet.
(And I might be wrong, but let's not start a conversation about the cognitive abilities of infants. Cool guys?)