Re: latching relays

On Mon, 10 Feb 2025 18:49:04 +0000, Michael J. Mahon wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:

On 10/02/2025 12:33, Joe wrote:

On Mon, 10 Feb 2025 09:12:32 +0000, Mike Scott
<usenet.16@scottsonline.org.uk.invalid> wrote:
 

Hi all. I think a latching relay is the way to go for a pico-based job I
have in mind. However the prevalent ones all seem to be controlled by a
pulse on a single input wire which flips and flops the state.
 
No doubt they reset to a known-state at power-up. But I see no
indication of any way of resetting them to that known state without
turning off the power - eg after reloading the pico control program.
 
Has anyone used these and can offer advice please? Thanks.

I am using the HFD2/005-S-L2-D dual coil relays.  They work for my purpose....
 
See: https://source.hongfa.com//Api/DownloadPdf/323

 
Thanks for the reply. I was considering complete units (like eg url
below (*)), which differ in operation. They take a pulse on a single
logic-level input, and flip-flop between states: my query is how to
reset from a random state to the power-up state.
 
The one you reference uses either reverse polarity or a 2nd coil to flip
and flop.
 
 
 
(*)
<https://www.amazon.co.uk/%E3%80%90%F0%9D%90%84%F0%9D%90%9A%F0%9D%90%AC%F0%9D%90%AD%F0%9D%90%9E%F0%9D%90%AB-%F0%9D%90%8F%F0%9D%90%AB%F0%9D%90%A8%F0%9D%90%A6%F0%9D%90%A8%F0%9D%90%AD%F0%9D%90%A2%F0%9D%90%A8%F0%9D%90%A7%E3%80%91-Flip-Flop-Self-Locking-Bistable/dp/B08LCTTR4Z/ref=sr_1_6?crid=1X3LJ40EW31PS&dib=eyJ2IjoiMSJ9.RT0p7Xw5aJ0Swdoibedry1USbeWgVfw825dY065GrU69oETh7LUKVWnWUjyVpSszgw3nD-k3IJb0JqTj4_dub2sNKoCG5RiD66Y0AXX_2FUXHDzt-3kELJdgbFjrV-fEzfWkFsXFRRZC4yqrRIh2DzCvMEDlqaV1C66gP9H9OtABUWO3miMmsfqPY2OvxIz4ORJ-gEzJ81GrtiW30IbGrE9nNDx5D6MQ_hjlXLgsBaq1iAptiO6lvwn31IMh4vJXsSVS3a7ckkG1MO4Z6DWTI1Og3Tw5QgXRDR7L9c07Uk7Mtd0mccGx33TGtHFf0Q7I_ojHzk-TeNSON2usCmhqoBpo3qK7DbckUoRsRbuv2TLMwKsO_4fpMxQxZk8ba4n19QVDlRdXVJedgWzL5ye6aH0bLnlc5tk1Bk9IsieO-wIIDOqHja6LmsdPjwi52Ltq.uR8nBzN6Nf-BBzOjkOcmfdgfxpIuRN1Ed4Spc0VtRUA&dib_tag=se&keywords=5v+dpdt+latching+relay&qid=1739195865&sprefix=%2Caps%2C72&sr=8-6>
 
(No, I'd not pay that sort of price :-) )
 

 
In that case, the only reliable way to proceed is to provide a way to sense
the current state of the relay so that the desired state can be selected.

Such as an extra pole that you could connect to a sense input to poll
and check the relay state.