lucca brassi
Enlightened
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!
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 .
---------------------------------------------------------------------
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!
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