Continue to Site

# Latching Reed Switch or Alternative?

Status
Not open for further replies.

#### TwoPlank

##### New Member
I've been looking for a latching reed switch or some sort of alternative for a project of mine. I've searche the General Electronics Chat forum, but couldn't find an answer. I'm VERY new to electronics, but I'm trying to set up a simple circuit with a latching reed switch, miniature vibrating motor (pager motor), and a coin cell battery that will be sealed in an a capsule about the size of walnut shell. I've been experimenting with reed switches (form A?), but I need a switch that I can turn on and off (form E?). I've found a switch I think will work, but I'm not sure. It's made my Meder and it's part# MK6-4-E, but I haven't been able to find where I can purchase just a few of them, plus they cost a little more than I'm looking to spend. If there is an alternative to that part that someone can recommend or a simple setup that would work for my applicatoin, I would really appreciate it! Please let me know if you have any questions or need any additional information to help me come up with a solution.

#### blueroomelectronics

##### Well-Known Member
Latching reed switch nope. How would you unlatch it? Maybe an SCR would work in your circuit.

#### MikeMl

##### Well-Known Member
Are you trying to use the latching feature as a "zero power" memory?

A latching reed relay is just a glass-encapsulated reed switch which is "biased" by a permanent bar magnet. The coil is pulsed with one polarity where the magnetic flux adds to that from the magnet to latch the points closed, and the opposite polarity in the coil opposes the magnet to unlatch.

#### Ross Craney

##### New Member
but I need a switch that I can turn on and off (form E?).

You can get reed switches with changeover contacts if that is what you are looking for. They are easy to get & inexpensive.

#### blueroomelectronics

##### Well-Known Member
I've never seen reed switches with changeover contacts, neat. Do you have a part number?

#### Ross Craney

##### New Member
bluey - Jaycar (Australia) part # LA5070
$6.25 (aus$) each \$4.95 for 10+ I use em all the time for customised electronic security applications

#### Mr RB

##### Well-Known Member
I would use 2 reed switches and an SCR (as Blueroom suggested). One reed turns it on, the other shorts the SCR causing it to turn off. That would be the most energy efficient setup since you wont have much energy reserve with a coin cell.

#### Ross Craney

##### New Member
There is a minimum "latching" current (anode to cathode) below which the SCR will not stay latched. He may need to choose his SCR very carefully.

#### Mr RB

##### Well-Known Member
Agreed.

C106D, TO126, Ion=0.2mA, Ihold=5mA
C103B, TO92, Ion=0.2mA, Ihold=5mA

Both are common enough. However the forward voltage may be too high, I'm thinking he might need 2 coin cells. That might still fit.

Here's an off the wall thought, what about an inertially operated switch? Get a miniature toggle switch, epoxy a lead sinker to the end of the lever and glue it in the waterproof capsule with battery and motor. A harsh impact would flip the switch either on or off, depending which way you impact it.

#### floyd955

##### New Member
Latching Reed Switches

There are latching reed switchs out there in the SPDT configuration.
How much current are you talking about and what is the switching frequency of the circuit you are trying to control.
Look at Hermetic Switch Inc. Model HSR-638BSL Form C Bi-Stable Latcher.

#### mneary

##### New Member
OP hasn't logged on since posting the question.... lots of people do that.

Status
Not open for further replies.

Replies
4
Views
680
Replies
2
Views
735
Replies
7
Views
615
Replies
2
Views
661
Replies
12
Views
8K