Hi all. I think a latching relay is the way to go for a pico-based job II am using the HFD2/005-S-L2-D dual coil relays. They work for my purpose....
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.
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 II am using the HFD2/005-S-L2-D dual coil relays. They work for my purpose....
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.
See: https://source.hongfa.com//Api/DownloadPdf/323
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 aI am using the HFD2/005-S-L2-D dual coil relays. They work for my purpose....
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.
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-
(No, I'd not pay that sort of price :-) )
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.
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.
Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:Bistable/dp/B08LCTTR4Z/ref=sr_1_6?crid=1X3LJ40EW31PS&dib=eyJ2IjoiMSJ9.RT0p7Xw5aJ0Swdoibedry1USbeWgVfw825dY065GrU69oETh7LUKVWnWUjyVpSszgw3nD-k3IJb0JqTj4_dub2sNKoCG5RiD66Y0AXX_2FUXHDzt-3kELJdgbFjrV-
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.I am using the HFD2/005-S-L2-D dual coil relays. They work for my purpose....
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.
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-
(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.
On 2025-02-10, Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:
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/dp/B08LCTTR4Z/ ]
Those are not conventional latching relays but standard one with
an external latching circuit. The semantics oare defiferent.
latching relays use two coildand don't need power to maintain their
state. The page tells you all you need to know, namely the relay
is not energised when power is first applied, so conductivity is
between NCx and COMx, switching to NOx and COMx on the first pulse.
Lack of proper data sheets is one of the reasons I'm not generally
a fan of commercial building block modules like this.
OK, I get it. I'm after something that'll retain the same setting for extended periods, hence the desire for a latching relay to keep power dissipation down. Indeed, it does look as though what I've been looking at is a normal relay plus a flip-flop - not what I want, and I think you've saved me from a bad mistake.
Not wanting to mess with relay driver circuitry, I've found something
that's definitely latching at PiHut (I hope!!). Pricey, but complete
modules don't seem available otherwise.
Thanks to all for commenting.
In message <vofpqt$1qm8g$1@dont-email.me>The one thing: You HAVE to prevent your control circuit (like Arduino) from sending spurious signals to the relay on power-up to
Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:
OK, I get it. I'm after something that'll retain the same setting for
extended periods, hence the desire for a latching relay to keep power
dissipation down. Indeed, it does look as though what I've been looking at >> is a normal relay plus a flip-flop - not what I want, and I think you've
saved me from a bad mistake.
Not wanting to mess with relay driver circuitry, I've found something
that's definitely latching at PiHut (I hope!!). Pricey, but complete
modules don't seem available otherwise.
Thanks to all for commenting.
Look at the Hongfa HFD2 data sheet. The range includes single side
stable (i.e. an "ordinary" relay), 1 coil latching, and 2 coils
laching, and shows how to connect and how to energise to get latching
relays of either type into the state you want.
The latching relays are the real thing; they retain state indefinitely, >without power, after being set to either state.
David
In message <vocfu0$14uka$1@dont-email.me>Yes they remain their state BUT sometimes Arduino likes (from experience) & probably Raspi's give of spurious pulses on startup
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.
It has always been my understanding that they retain their current state >indefinitely, until the next pulse. So there is no such thing as a
reset state.
David
Yes they remain their state BUT sometimes Arduino likes (from experience) & probably Raspi's give of spurious pulses on startup which can be/needs to
be prevented:
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