Magnetic Latching Switch - ideas?

I would like to use a “magnetic latching switch” for turning a circuit on & off using a low-power magnet. I saw the US1881 Hall switch, which would seem to be an ideal solution; however, the datasheet says that it is rated for 50mA (max).

For my project, I would like to switch on & off the positive terminal of a 7.4v battery. My circuit draws up to 170mA.

I’m a bit confused (I never worked with these kind of switches before), and hence, I could really use some suggestions & ideas. Perhaps I should take a different approach?

Thanks :slight_smile:

using a low-power magnet

If you add a driver transistor to the output of the sensor you can achieve what you want. Have you experience with MOS fets or bipolar transistors?

My circuit draws up to 170mA.

What is your load?

You do know it takes one pole magnet to turn it on and the other pole magnet to turn it off, it is not a toggle in the normal sense of the word.

Also normally the outputs are open collector NPN transistors so you would have to invert that to switch a positive battery connector.

Why not using Reed switch?It can take higher current.

Could it be that what you are looking for is a latching relay? Apply one polarity pulse and it operates and the opposite to turn it off. Use H bridge driver to control it.

Weedpharma

Greensprings: use the logic of the arduino to do the toggle and a relay/transistor

A relay should not be be connected direct to the outputs due to back EMF (preferred even if diode used). You would also need two relays, one to pulse and one to reverse the polarity.

Please show how this can be done with transistors without using a H bridge circuit.

The H bridge driver is a simpler, neater way to do the job.

Weedpharma

Greensprings: weedpharma, do you farm weed?

just write code to read an input from the hall signal and send a driver signal to whatever you need to control your power, mosfet, transistor, vacuum tube, however, whatever

I farm weeds of various types.

Th OP refers to a magnetic latching switch. None of the devices you mention match this description.

Other responses have also spoken of magnetic devices and the need to reverse the polarity.

Weedpharma

Thanks guys for all the suggestions. These give me some great starting pointers :)

I just came across this pushbutton power switch from pololu (http://www.pololu.com/product/750). It looks like it might be a interesting option. I could maybe replace the "push switch" with a hall effect sensor (thanks BillHo for the tip) so that it acts as the switch. Grumpy_Mike, thanks... yes, I realize that I would have to turn the magnet around in order to expose the other pole to a US1881 in order to "toggle it".

I wonder if Pololu's switch itself (not counting the load) would have a very low power draw when it is activated. It looks like it only draws microamps when it is switched "off"...

Very interesting options out there... I'm learning a lot from everyone's comments. Thanks!

BillHo: Why not using Reed switch?It can take higher current.

High current ones can, but the smaller, lower current type will weld their contacts together if you try to switch too much current.