latching relay driver circuit

[rainman1]

Hey,

I dont manage to understand how this driver circuit works.
Why did they draw the same circuit twice?
What do the LATCH and UNLATCH input mean?

I understand how the driver circuit for latching relay should work,
but just dont get how this circuit do the job.

Here is the circuit: https://www.electro-tech-online.com/custompdfs/2009/01/LATCHRELAY1.pdf
I would be happy with any help.

Thank you very much.

 

[ronsimpson]

A normal relay is "on" when and only when power is applies to the coil. It is "off" then no power is applied.

A latching relay has two coils. Whey you first get the relay it may be ON or OFF we don't know. Apply power to the on-coil for more than 25mS will cause the relay to be ON. It will stay ON for years with out power.

To turn off the relay apply power to the off-coil for a short period of time and now the relay is OFF. Sending power to the off-coil again will not shange anything.

 

[rainman1]

Thanks!
So this isnt a single coil latching relay,
but a dual coil latching relay?
The input needs to be a 6V pulse?

If it is a dual coil driver, could i use this circuit for a single coil relay?
I mean, is there any change i could make in the circuit so a positive current would flow through the coil in the input's rise, and a negative current would flow through the coil in the input's fall?

 

[ronsimpson]

I don't see how.

 

[rainman1]

Thanks.
Do you know where i could find one that uses common components like capacitors, transistors and resistors?

 

[ronsimpson]

I need to know more about what you want to do.
The diagram you have is how to use a 6 volt coil relay on a 3 volt supply. It will be much better if you have 6 volts or 5 volts to drive the relay.
What supplys?

 

[rainman1]

I have a 5V single coil relay, a single +5VDC supply and a single +3VDC supply.
A microcontroller provides the 3V supply, so i can create a 3V pulse for the driver circuit need.
My goal is to design a driver circuit for this latching relay with common components - transistors, diodes, resistors, capacitors.
Since i would want to save in power consumption of the driver circuit, i'd want the relay to switch states in every 3V pulse.
For that design, I would probably need to add an addition control leg which will determine which 3V pulse will cause negative current flow through the coil, and which 3V pulse will cause a possitive current flow through the coil.

Thanks for any help.

 

[DSchabel]

I have a 5V single coil relay, a single +5VDC supply and a single +3VDC supply.
A microcontroller provides the 3V supply, so i can create a 3V pulse for the driver circuit need.
My goal is to design a driver circuit for this latching relay with common components - transistors, diodes, resistors, capacitors.
Since i would want to save in power consumption of the driver circuit, i'd want the relay to switch states in every 3V pulse.
For that design, I would probably need to add an addition control leg which will determine which 3V pulse will cause negative current flow through the coil, and which 3V pulse will cause a possitive current flow through the coil.

Thanks for any help.

You need a low-power H-bridge. You can buy them in a package, or design them with discrete components.

Since you don't have much spare voltage. you should probably use 2 p-channel FETs, and 2 n-channel FETs. Normally, if you were driving a coil which could store any significant energy, you'd want to add catch diodes, but in this case you can probably use the lower FETs' (the N-channel ones) internal parasitic diodes for 2 of the 4.

 

[swagatam]

Simple relay latching circuit schematics: **broken link removed**