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Reed switch interfacing with battery.

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sreekanthm

New Member
Dear all,
I have designed a battery(Lithium-Ion,7.2 V,5.2 amp/Hr) operated instrument.Instrument when switched on takes 0.5 amp of current.

I have connected a reed switch (RI- 25C,coto technology) having switching current capacity of 1 amp and continuous carry current of 3 amp in series to battery.

Reed switch closes when magnet is brought near to it and opens when it is taken away.

Problem is when i interface the reed switch with the battery and bring the magnet neat to it ,it closes and the instrument is powered,but when i bring the magnet away from the reed switch it still remains closed only untill and unless it is shook to open.

Please help me out.


Thanks and Regards
Sreekanth
 

Techie7

Member
What instrument you are powering?

That seems like a faulty reed switch IMO. Could be magnetized permanently a little.
 

sreekanthm

New Member
MR.Techie 7 Thankq .

Yes i have tried by replacing it with the new one also.

It did not work.

I mean it is also closing when the magnet is brought near to it and does not open even when the magnet is brought is brought away from it.It opens only when manually shaken to open.

Regards
Sreekanth.M
 

ericgibbs

Well-Known Member
Most Helpful Member
Dear all,

I have connected a reed switch (RI- 25C,coto technology) having switching current capacity of 1 amp and continuous carry current of 3 amp in series to battery.
Sreekanth
hi,
Are you saying the reed is switching 3A when its operated.? and its rated switching is 1A.

If so, it sounds as though the contacts are becoming 'flash' welded with the 3A current.
 
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sreekanthm

New Member
Thanks MR.ericgibbs,

What i mean is , reed switch has the capacity to carry 3A of continuous current and the switching current capacity of it is 1A.

But my instrument when switched can consume only 0.5A which is well within the range of reed switch switching current range.

And my instrument during its operation can take 1.5A max which is also well within the continuous carry current of reed switch.

Regards,
Sreekanth
 

ericgibbs

Well-Known Member
Most Helpful Member
Where in the circuit is the reed switch contact.?

Do you have any high value capacitors after the reed.?, for smoothing etc.
 

sreekanthm

New Member
Reed switch interfacing porblem

Thanks ,MR.Ericgibbs,
I am using small capacitors of value 33pf or 0.1µf.It did not work.
Does it have any change when we go for higher value of capacitors.
I ll try it with 100µf capacitor.

Regards
Sreekanth
 

ericgibbs

Well-Known Member
Most Helpful Member
Thanks ,MR.Ericgibbs,
I am using small capacitors of value 33pf or 0.1µf.It did not work.
Does it have any change when we go for higher value of capacitors.
I ll try it with 100µf capacitor.

Regards
Sreekanth

I wouldnt increase the cap, I thought if you had already got a large cap on the rail, say 1000uF, charging that could weld the reed contacts.
 

Techie7

Member
I would suggest a simple method for testing your reed switches whether functioning correctly or not. Just try to light up an LED through a series of current limiting resistor(100E) and reed switch connected to a 3v battery(2 x 1.5v).
 

sreekanthm

New Member
Mr.Ericgibbs,

yes i do have capacitor of 1000µf in the circuit.I am using Photo multiplier in the instrument which needs high voltage.The supporting circuit of high voltage consists this capacitor.Capacitor does not immediately follow the reed switch.

The same reed switch when connected with a variable power supply(max current is 2A,12V) and operated it is working fine.

But if i use battery instead of power supply,the problem is occurring.


Regards,
Sreekanth
 

sreekanthm

New Member
reed switch interfacing problem

MR.Techie7,
The same reed switch when connected to the external variable power supply(2A,12V) and powered by bringing the magnet near to it ,it is working. It opens when the magnet is brought away from it.so everything is fine with the external power supply.It is causing problem with the battery.

what can be the problems.

Thansk & Regards
Sreekanth
 

Sceadwian

Banned
That's makes no sense.. Something else has to be going on.
 

ericgibbs

Well-Known Member
Most Helpful Member
WHY have you started another thread for the SAME question.:confused:
 

kpatz

New Member
Is there anything near the reed switch that might be generating a magnetic field that could be holding the switch closed, such as a transformer or speaker?

Otherwise, maybe the contacts are sparking, causing them to spot weld. Maybe try a small (.1uf) cap across the reed switch to absorb transients will help.
 
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