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Latching Relay

S

Sparkie

Jan 1, 1970
0
I am putting together a project which is designed around low power DC
(battery driven), and that ultimately results in a high (+5v) or low
(0v/ground) - a simple change of state to pin out of IC. I have good
control over this output, and can provide assertion high or low, or
indeed momentary.

I intend to then couple this output through a darlington transistor
pair to provide the necessary current for a relay to then switch mains
power and operate a mains powered device (eg. a light bulb).

The problem I have is:
As the project is battery driven, I MUST be as frugal as possible with
current drain. I cannot afford any power drain from the battery when
the relay is in operation and the mains powered device is on.

What I have considered:
Latching relay - I think these work by providing a brief trigger to
energise the coil, the n/o contact is somehow strapped to the load
side, which then latches the relay on after trigger. Reset would
require a break in the coil leg to ground/0v. Have I understood this
correctly? Will there be no further drain from battery after initial
trigger?

This initially appear the answer, but as my output is from 1 IC pin
only (high, low or blip), I am left wondering how to design my cct to
trigger and re-set the relay?

Magnetic latching relay - this looks like a strong possibility. I could
set my output to momentary, then each time pin assertion, the relay is
triggered and toggled on or off. I believe because these relay on
magnets, that they do not use or require current to maintain state?

I don't understand the above working designs / options of these relays
enough to be confident within my design, could someone help me with my
understanding and perhaps make comment to my original project
requirement (ie. battery control, switch on/off of mains power, no
battery draw when coil/switch is energised).

MANY thanks,

Ian.
 
S

Stanislaw Flatto

Jan 1, 1970
0
Sparkie said:
I don't understand the above working designs / options of these relays
enough to be confident within my design, could someone help me with my
understanding and perhaps make comment to my original project
requirement (ie. battery control, switch on/off of mains power, no
battery draw when coil/switch is energised).

MANY thanks,

Ian.

There are two versions: Dual coil and single coil-dual polarity, both
retain the last state by magnetic latching in position last ordered.
Don't know what external device you want to control but after activation
you can pack your cirquit and take it home and the relay will still
activate the external device, so some "zeroing" action should be
implemented on initial power on of the cirquit.
You are mentioning the current of your battery so, if I would have to
design such would do something like:
two separate 5v relays capable of carrying on their contacts the
currents AND voltages of the main line contactor. One normally open and
one normally closed. Line contactors usually sport additional contacts
that can perform the self holding function. So your N/O relay acts as a
push button to supply line to main coil, the coil enters self holding
condition and the relay can relax. The other side of the main coil is
connected to the N/C relay and activating it stops the whole mess.
So the relay acivations are temporary, when needed.
The rest is just "logic" left as an excersise for you.

Happy hunting

Stanislaw
Slack user from Ulladulla.
 
S

Stanislaw Flatto

Jan 1, 1970
0
Stanislaw Flatto wrote:

Long time since I used magnetic latches relays and I don't recall if
such exist for 5v range. The ones in my work were the 28v style, and
needed proper push to change states.
At least they don't use current when left alone.

Good luck

Stanislaw
Slack user from Ulladulla
 
J

John Fields

Jan 1, 1970
0
Stanislaw Flatto wrote:

Long time since I used magnetic latches relays and I don't recall if
such exist for 5v range.
 
S

Stanislaw Flatto

Jan 1, 1970
0
John Fields wrote:

Google is your friend.

It is now, we did not have such luxury then, it was a a library of
manufacturers catalogs (tons of it) and a large collection of
Mil-Speck visual tapes to be read on magnifying screen.
Somehow we survived it.

Have fun

Stanislaw
Slack user from Ulladulla.
 
K

kell

Jan 1, 1970
0
Sparkie said:
I am putting together a project which is designed around low power DC
(battery driven), and that ultimately results in a high (+5v) or low
(0v/ground) - a simple change of state to pin out of IC. I have good
control over this output, and can provide assertion high or low, or
indeed momentary.

I intend to then couple this output through a darlington transistor
pair to provide the necessary current for a relay to then switch mains
power and operate a mains powered device (eg. a light bulb).

The problem I have is:
As the project is battery driven, I MUST be as frugal as possible with
current drain. I cannot afford any power drain from the battery when
the relay is in operation and the mains powered device is on.

What I have considered:
Latching relay - I think these work by providing a brief trigger to
energise the coil, the n/o contact is somehow strapped to the load
side, which then latches the relay on after trigger. Reset would
require a break in the coil leg to ground/0v. Have I understood this
correctly? Will there be no further drain from battery after initial
trigger?

This initially appear the answer, but as my output is from 1 IC pin
only (high, low or blip), I am left wondering how to design my cct to
trigger and re-set the relay?

Magnetic latching relay - this looks like a strong possibility. I could
set my output to momentary, then each time pin assertion, the relay is
triggered and toggled on or off. I believe because these relay on
magnets, that they do not use or require current to maintain state?

I don't understand the above working designs / options of these relays
enough to be confident within my design, could someone help me with my
understanding and perhaps make comment to my original project
requirement (ie. battery control, switch on/off of mains power, no
battery draw when coil/switch is energised).

MANY thanks,

Ian.

You may wish to consider an alternating relay, which latches
mechanically.
Each momentary actuation of the coil toggles the relay contacts and
locks them in the opposite position.
 
F

Fred Bloggs

Jan 1, 1970
0
I am putting together a project which is designed around low power DC
(battery driven), and that ultimately results in a high (+5v) or low
(0v/ground) - a simple change of state to pin out of IC. I have good
control over this output, and can provide assertion high or low, or
indeed momentary.

I intend to then couple this output through a darlington transistor
pair to provide the necessary current for a relay to then switch mains
power and operate a mains powered device (eg. a light bulb).

The problem I have is:
As the project is battery driven, I MUST be as frugal as possible with
current drain. I cannot afford any power drain from the battery when
the relay is in operation and the mains powered device is on.

What I have considered:
Latching relay - I think these work by providing a brief trigger to
energise the coil, the n/o contact is somehow strapped to the load
side, which then latches the relay on after trigger. Reset would
require a break in the coil leg to ground/0v. Have I understood this
correctly? Will there be no further drain from battery after initial
trigger?

This initially appear the answer, but as my output is from 1 IC pin
only (high, low or blip), I am left wondering how to design my cct to
trigger and re-set the relay?

Magnetic latching relay - this looks like a strong possibility. I could
set my output to momentary, then each time pin assertion, the relay is
triggered and toggled on or off. I believe because these relay on
magnets, that they do not use or require current to maintain state?

I don't understand the above working designs / options of these relays
enough to be confident within my design, could someone help me with my
understanding and perhaps make comment to my original project
requirement (ie. battery control, switch on/off of mains power, no
battery draw when coil/switch is energised).

A typical datasheet is here:
http://rocky.digikey.com/WebLib/Omron Web Data/G6J-Y Series.pdf
This is a single coil version, see pdf page 7 for pinout on G6JU
latching version which indicates coil current into pin 1 and out pin 8
is "S" for Set, and current into pin 8 and out pin 1 is "R" for Reset,
the diagrams show the configuration of pins 2-7 in the Reset state,
presumably, since this is the default factory setting at shipment.
According to the datasheet, the coil requires an approximately 20mA
pulse of duration 10ms maximum to guarantee state change at 5V. The most
uncomplicated way to drive this particular relay with your circuit
arrangement is to use a series capacitor like so:
View in a fixed-width font such as Courier.
 
I

ian field

Jan 1, 1970
0
Stanislaw Flatto said:
There are two versions: Dual coil and single coil-dual polarity, both
retain the last state by magnetic latching in position last ordered.
<snip>

IIRC - that's a carpenter relay.
 
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