Dive switches

[lucca brassi]

May I ask you what is yours opinion about HALL switch ( not sensor ! )
To be concrete ;something like that :
http://www.melexis.com/Assets/US5881_DataSheet_4824.aspx
(similar switches can be found in computer fans - they count RPMs)

- you have to be careful there are two types of hall switches :
- UNIPOLAR ( that we use - switches normally only on J-south pole )
- BIPOLAR ( they switches when switch go through change of magnetic field J-S (hysteresis ) and they are normaly used in computer fan brushless motors)

I have for myself a little separated feeling about that topic. so I wrote PROs and CONs

POSITIVE
-it is smaller then REED
-it is cheap
-it is much more simple to orientate in correct position (only one)
-simple to build in
-switches only on SOUTH pole magnet
-senses weak magnet field ( thick walls of enclosure- have choice between low /medium/high sensitivity version of switch-look datasheet)
-no sticking sticking of contact foils in REED capsule
-can be almost directly exchange REED in combination with few components (reed , resistor ,n-MOSFET)
-clean switching hysteresis (pulse)- built in schmidt trigger ( in case of half magnetised contact leafs in reed capsule)


NEGATIVE
- takes little current (2,5mA- in operation time , between traveling it is normal to disconect battery)
- needs another POWER component to switch power current (also REED need relay or FET too)

So what is yours opinion .

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About PIEZO :

I have see several lamps built with piezo most from :
http://www.pcmus.com/Dive-Photos/Maglite-Canister-Dive-Light.htm
and some on MS MULTIPLY but....
- in fact this is keyswitch (not normal switch(( push and hold) even they exsist that too))
- to big switch
- to expensive
- not right environment for that kind sensor (it is IP67-68 but because of technology of sealing-encapulating -it is mean for harsh environment )
- need aditional switching circuit ( it is not problem but... (debouncing))
- it is too sensitive (detects quick pressure difference - in water it is pressure all the time but it is constant)

..... dont like it at all!

 

[Packhorse]

I cant comment on hall effect sensors or switches as I have not used them.

But I can say the only problem I have had with reed switches is breaking them during installation.

I have never had them stick.
I have only ever used 3 components. Mosfet, reed & resistor.
Cost is $2nz or less. Its not an issue.

hall effect sensors/ switches may be better. I just have not tried them

 

[SUBjohan]

May I ask you what is yours opinion

I have never used them but I think I am going to use them in my new project, it looks like a nice upgrade above a reed switch.

Thanx for the heads up :thumbsup:

Greetz Johan

 

[gt40]

I found this link which explains usage of hall effect switch in non ee terms. They are using it to build a motor but the principle would work the same if you used it as a trigger switch with a fet.

http://www.simplemotor.com/hallswitch.htm

 

[DIWdiver]

Hall effect switches

In case that link didn't explain it well enough, a Hall Effect Switch is an integrated circuit that has three pins - power, ground, and output. The output changes in the presence of a magnet.

I love hall switches (used 3 in my light), but they are definitely not suitable for all applications. I think the primary benefit in dive lights is that they can be very small, like 0.1 - 0.2 inches square. The primary drawback is that they draw power all the time. Most are in the 5-20 mA range. There are some much lower than that, but they have very limited voltage range, making them more difficult to use.

With small neodymium magnets, many hall switches will operate at distances of 0.25" or more, which I think is comparable to typical low-current reed switches (someone please correct me if I'm wrong).

Another problem with hall switches is that there are many to choose from, and they have VERY different behaviors and specifications. Unless you can read and understand the data sheets, you should probably depend on someone else to suggest an appropriate part for your application. If anyone is really itching to try them out and needs assistance, PM me and I'll see if I can help.

D

 

[DIWdiver]

Magnetic switches

There is a large manufacturer that used reed switches for many years - Princeton Tec. The TEC-400 that I have used for years uses a reed switch. It's simple and cheap. When the reed switch on mine broke, I was able to replace it.

The main drawback of magnetic switches that I have seen is the magnet.

I dive wrecks mostly, and the magnet is always picking up fine iron particles. They get in the sliding mechanism, making it hard to operate. They also can extend the magnetic field of the magnet, making it hard to turn off the light. You can clean it with the spray nozzle on a hose, but you can't do that during a dive!

 

[350xfire]

By far the easiest is to use the toggle with boot. Now, the problem lies in which boot you use. Most of us DIYers frequent Ebay for parts. We search toggle boot and are lured in by the $2.25 free shipping toggle boot. Believe me I fell for that one. Then I went to a surplus store and found some for about $1.25. They both sucked. They are pretty thin and flimsy. What happens is that, when pressurized, to lets say 260', the air in the boot is pressurized and the boot collapses around the toggle switch's shaft causing a tear at the bottom. I had about 2-3 failures like that.

I finally found a company APM Hexseal that has by far the best boots out there. So I ordered up some. Much thicker and better. If anyone wants any of these, let me know because I ordered plenty to take advantage of wholesale pricing.

 

[DIWdiver]

I wouldn't question that the toggle switch is by far the easiest to understand and implement. However it is also, IMHO, the most likely to fail.

 

[Z-Max]

The reed switch itself cannot take the kind of currents we use today.

This problem has the simple decision:

 

[kl3vr]

Excellent thread!
Thx for introducing me to Hall switches and the mosfet diagram!
Can the hall be used as a potentiometer of sorts, to control the brightness? I think it'd be such a quality feeling to gracefully ramp up the lumens instead of in modes. Plus it'd be the simplest UI. A diagram would be awesome.

*** What about a reed controlled hall switch! The reed is there only to turn on the hall switch when its needed. One magnet would turn on the reed, supplying power to the Hall, which would then tell the driver board how much to feed the lamp. Sounds like *fun* to assemble but I did say quality....

 

[lucca brassi]

or so : simple wet contacts

two SS screws in distance cca 5mm ... when submerged open gate of FET which starts to conduct .

when get out of water resistance grow and close gate.

and of course rescue LED from overheating....

 

[lucca brassi]

Can the hall be used as a potentiometer of sorts, to control the brightness?

Yes it could be but for use that you need hall sensor like that http://hallpot.com/ . Of course you can made it DIY with separated sensor inside can and potted magnet outside.

What about a reed controlled hall switch .The reed is there only to turn on the hall switch when its needed. One magnet would turn on the reed, supplying power to the Hall, which would then tell the driver board how much to feed the lamp. !

....

It can be but DIR guys will kill you for that Actualy if you dive with canister light you can put ON-OFF-ON(Momentary) for example toggle switch which can on one side work strictly direct and on other side via gadgets like hallpot or via uC. (Hanchan don't read this )) You right - corected

 

[hanachan]

i think a LED is (still) ON above water in this circuit.
because the gate impedance is very high.

 

[kl3vr]

Quote:
Can the hall be used as a potentiometer of sorts, to control the brightness?
Yes it could be but for use that you need hall sensor like that http://hallpot.com/ . Of course you can made it DIY with separated sensor inside can and potted magnet outside.

I like the all in one solution the hallpot offers, but I couldn't handle it constantly draining my battery just sitting on the shelf. Yes you can unscrew the cap but thats not very classy

I'm new to the custom scene, and I thank you all for providing these great links to companies, but how does a person go about ordering their products? Is it common for CPF'rs to email requesting single item orders?

 

[lucca brassi]

Because I'm in laboratory scene I can sometimes handle direct to the companies with some samples from salesman.
For others look at their catalogue , find datasheet and sometimes you can pick even free samples

Otherwise take simple some local or web shop with electronics. For me they are interesting those in Europe because I don't pay tax.

I like farnell from UK because I get ordered sometime less in 24h ,
costsof package are similar to go with car in 55 main city Ljubljana ... but I culd get out there with empty hands .

so UK:
http://www.farnell.com/

http://uk.rs-online.com/web/

german :

http://www.conrad.de/ce/

https://www.buerklin.com/default.asp?l=e

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these shops I think have almost everything for example sensor like linked on the top:

http://si.farnell.com/jsp/search/br...t=potentiometer+hall&Ntx=mode+matchallpartial

or other hall switches and joysticks

http://si.farnell.com/jsp/search/browse.jsp?N=1003458

 

[DIWdiver]

kl3vr -

You don't say where you are located, but in the US there are many distributors that you can order small quantities (1 piece) from. Some of my favorites are:

Digikey.com
Mouser.com
Newark.com
Futureelectronics.com
Avnet.com
Alliedelec.com

These are all major distributors of new parts. All of them will sell to anyone with a credit card (except I haven't checked Avnet or Allied).

D

 

[DIWdiver]

Yes it could be but for use that you need hall sensor like that http://hallpot.com/ . Of course you can made it DIY with separated sensor inside can and potted magnet outside.

That's a cool idea!

It seems to me like it would need a microprocessor to make it work well, because the output vs. position is a sine wave, which won't work well with an LED, but now you have me thinking. I love/hate it when people do that!

D

 

[lucca brassi]

Sin/cos reading is normal used in digital calipers ( capacitive plates ) or other encoders.

 

[blackdiver]

Does anybody know how the Greenforce dimmers are working in combination with a boost driver? They work with power off and on quickly but what kind of a board and how to connect it??

Arjan

 

[kl3vr]

I was waiting for someone more knowledgeable to answer your question but I'll tell you what I can.
They use PWM (pulse width modulation) to turn on and off like a tv.
A driver:
http://www.taskled.com/d2flex.html
I'll let someone else explain how to wire it up.