A little relay help

I'm presuming that you want constant voltage on the Tortoise switch input for each direction change.  Looks like programming the AIU for standard switches and using the Interlocking feature would do the trick.  You'd wire relay #1 to one side, relay #2 to the other side.  I think you can use a single switch channel on the AIU to trigger this, they just output a momentary signal, that's what it appears the Interlocking features requires to latch it's outputs.

milwrd posted:

...

when S1 S1 pressed the relay; When pressed S1 S2 disconnected, S2's relay. 2-way interlocking only way to turn, you can also add the...

I agree with GRJ that the Interlocking function is the key.  Did you mess with the module to see how the Interlocking mode works; I don't understand the words above in bold?

It seems you are trying to emulate the DPDT latching relay method (as suggested by MTH for use with an AIU to control Tortoise) by using 2 SPDT relays.  You'd want Interlocking to be: Press S1 to turn on Relay 1 and Relay 2.  Press S2 to turn off Relay 1 and Relay 2.  The AIU relay outputs close momentarily of exactly 0.5 sec when you press either the turnout or straight buttons on the DCS remote. 

Separately, two comments:

1. While the module offers latching behavior, this obviously applies only for as long as power is applied.  The relays will obviously all turn off when you remove power at the end of a session.  Unclear from description if the module has "non-volatile" memory and the relays return to the last state when power is restored (I tend to doubt it).  This may be a non-issue but it is different from how the genuine latching relay behaves. 

2. I see on eBay these "latching" relay modules go for just under $2 per SPDT relay...so, say, $3 for DPDT relay functionality.  You can buy genuine DPDT latching relays suitable for driving a Tortoise for about $2, though arguably tedious soldering/wiring would be involved to bring them out to screw-terminal blocks like on your eBay module.  Assembled latching DPDT relay modules with screw-terminals go for about $10 per relay.  The latching relay as suggested by MTH on their website runs about $35 and requires soldering/wiring.  Just confirming we're on the same page here...

You could just leave the 5V power on the relay pack if you wanted it to retain the settings, I doubt it pulls much current.  It does look like a convenient way to convert the AIU outputs to Tortoise motors at low cost with minimal soldering.

I had some time to do some more testing. With the as delivered board I applied 12V to the two left terminals of the 8 position screw pad on the lower left in the pic (DC+/DC-) and a LED lights up to indicate power is on. With all of the jumpers in the stock positions I can press the S1 button and the relay on the upper left closes the N/O relay and stays closed until you press the button again, the same applies for S2 thru S6 buttons. When I move the jumper to the upper right of the screw pad (middle of the board) from the top position (self-locking) to the middle (interlocking) position the S1 relay closes and stays closed until you push S2 which closes S2 and opens S1. This repeats that sequence for the rest of the relays. When the jumper is moved to the bottom position (trigger) when pressing the S1 button the relay ONLY stays closed for as long as you hold it down. The issue I was trying to figure out was how to incorporate my AIU into the circuit. When I was testing the voltage to the stock board on all of the channel positions (screw pad) they had 5V on them with the jumper to the far right (high/low trigger selection) set in the low voltage. I then moved my attention over to the jumpers on the left side of the board (VCC/GRD). I pulled both jumpers figuring that's what was needed to get my AIU into the circuit via the channel screw pad. I tried pulling the VCC first but still had 5 volts to CH1. I moved it from VCC jumper to the GND and bingo, no voltage on CH1. I hooked up the AIU using ground from my power supply (I'm using an old computer supply) and it's working. Hope you can make sense out of this.

The only caveat in this circuitry is the fact that I can turn the relay on and off with just one or both of the two switch buttons on the DCS remote. Not a big deal for me. As John mentioned, I was looking for a less expensive relay to accomplish this task and for $10 bucks delivered I can wire up three track switches (two relays for each switch) with this unit. If I wire these relays up so they default to the mains on the track when powered up that will work for me. As John stated, if I leave the the relays powered up they would retain there positions although I'd rather not do that.

One more question, where would 5.1/6.8 resistors come in to play? Did i miss something in the translation? LOL

milwrd posted:

One more question, where would 5.1/6.8 resistors come in to play? Did i miss something in the translation? LOL

How do you have the board wired to the AIU?  The resistors are to limit current if you use more than 5VDC to turn the relays on.  What do you use for a voltage source to run through the AIU relays to trigger this relay module?

Trigger voltage: LOW is 0-2.5V, high defaults to 3.5-5V (If 12V voltage trigger, you need series connection a 5.1-6.8K resistor; 24V voltage trigger, you need series connection a 15-22K resistor, otherwise it will burn the chip)

That's what they're trying to tell you with the above statement.

Hey John, as I mentioned in my post I'm using a computer supply for the power source. It's your basic 12v/5v/3v supply. The only power I'm currently using is the 12 volts as required to the screw pad (left two positions V+/V-). As far a triggering the relay I took one of the ground wires from the supply and hooked it up the "IN" terminal on the AIU. Then that comes out of the #1 position (AIU again) and goes to relay channel #1. Every time I press the straight button on the remote it turns the relay on or off.

DON'T run 12V directly into that relay board's inputs, you'll cook the input circuit.  That's what the 5.1K to 6.8K resistor is for, to limit the current!  Put the resistor in series with the input lead.  Alternatively, you can simply use the 5V leg of that supply to go to the AIU and the inputs, that won't require any limiting.

I guess I'm a little confused here. The description indicates a 12v supply to feed the board:

Module interfaces:

1.DC +: Module power supply, 12V DC+;

2.DC-: Module power supply , 12V DC- ;

Powering the board and putting signals into the input are to different things!  You power your train transformer with 120 volts, you wouldn't put that on the tracks!

The signal inputs to that board are 0 to 2.5 volts is a low, and 3.5 to 5.0 volts is a high.  NOTHING MORE THAN 5VDC SHOULD GO INTO THE INPUT SIGNAL PINS!

I can't state it any clearer than they did in the description you pasted into the first post.

Trigger voltage: LOW is 0-2.5V, high defaults to 3.5-5V (If 12V voltage trigger, you need series connection a 5.1-6.8K resistor; 24V voltage trigger, you need series connection a 15-22K resistor, otherwise it will burn the chip)

Being the Curious George that I am I picked up a 12V latching relay with the idea that I could use it to operate my Tortoise switch machines via my AIU. The problem I'm having is the lack of instructions. I am able to trigger them manually by pushing to button associated with the corresponding relay. I know that I'll need two relays to operate each switch machine. However, I am having an issue with figuring out how to connect them to my AIU. Anyone have any experience with these?

Here is a pic of the relay and what instructions/description I have. Any help would be appreciated. 

Thanks for your time

Milwrd

Please check the web-site below.

It should help you out. suggested by MTH on their website

Good Luck, John 

John, as I mentioned in my post above in the factory configuration and 12 volts plugged in to power the board I took some voltage readings. On the channels (1 thru 6) inputs I got 5 volts. This is with the high/low jumper on the right side on the board in the low position. When I move the jumper the the high position I have 10 volts. Now, if I pull both jumpers on the left side of the board VCC/GRD there is zero voltage at all six channels. I currently have it configured with the VCC jumpered, low voltage jumpered (5v) and using the power supply ground to the AIU going to channel #1 and it works.

So if I reinterpret the description I should pull the high/low jumper, pull the VCC jumper, plugin the GRD jumper and supply 5v to channel #1from the AIU. Good thing I don't have to make a living doing this stuff.

gunrunnerjohn posted:

DON'T run 12V directly into that relay board's inputs, you'll cook the input circuit.  That's what the 5.1K to 6.8K resistor is for, to limit the current!  Put the resistor in series with the input lead.  Alternatively, you can simply use the 5V leg of that supply to go to the AIU and the inputs, that won't require any limiting.

John has forgot more about electronics than I will ever know!!  John is correct!! That being said, I think this post may be misleading to some people.. The added resistors decrease the available voltage, therefore, as John states "limits the current"(amperage).. Basic electricity: V= I / R.. V=voltage, I = amps (current), R=resistance .. John please don't beat me up on this, it's just the 'old teacher' coming out... If I am incorrect, or out of order, please let me know.. I will delete my post..

If interlocking behaves as you described, I'd try the following.  If you set the module to "LOW" level triggering, you apply DC- to trigger.  Then just have the AIU apply DC-.  So each AIU SW channel drives two trigger channels set to interlock.  The two paired interlocking relays are always in opposition (one is ON when the other is OFF); thus by connecting NC to NC and NO to NO for the paired relays, this implements the criss-cross polarity-reversal wiring of a DPDT relay.

Until the first "trigger" to a pair of relays, they will both be OFF the first time power is applied. So leave power on forever to remember the latched positions, or perhaps use the DCS "Route" function to automatically set each pair of relays to the desired default direction at the beginning of each operating session.

Using low level triggering should eliminate the issue of dropping resistors on the trigger inputs.

Good point Stan, that will eliminate the need for the resistor.   Zero volts is one permissible input voltage within the input ratings.

With Stan's diagram in hand I gave this R&D project another try and think if this was a 2 channel relay it would work. Unfortunately the interlock design works like this: turn relay #1 on and it's latched. Turning relay #2 on or for that matter any of the remaining four remaining relays and #1 turns off. I also tried a different method of using a jumper between ch #1 and ch #2 in the the hope that I could turn both on at the same time using the diagram below (output only) for switch motor hookup. Only problem with this was they wouldn't both turn on or off together. My search continues.

Thanks for all the the help guys.

milwrd posted:

... Unfortunately the interlock design works like this: turn relay #1 on and it's latched. Turning relay #2 on or for that matter any of the remaining four remaining relays and #1 turns off...

So for the record, for this particular "latching" relay module, the interlock mode turns on relay #N and turns off all other relays...so only one relay is ever on at a time.  Activating relay 1 turns off 2,3,4,5,6.  Activating relay 2 turns off 1,3,4,5,6.  Activating relay 3 turns off 1,2,4,5,6.  And so on.  Do I have this right?

As you say, you can use just 2 of the 6 relays to make a one-channel Tortoise controller.  If you're paying only $10 for the module, that might be less than what you'd pay for a ready-to-go single DPDT latching relay module with screw-terminal connections!

Good point Stan. I bit bulky but doable. Thanks

In the lemon-lemonade category, see if this makes sense. 

Wire up 3 Tortoises to the 6 relays using the paired-relay hookup.  So relays 1&2 to the first Tortoise, relays 3&4 to the 2nd Tortoise, relays 5&6 to the 3rd Tortoise.  The key is to note that if both relays of a pair of OFF, then there is no drive to that Tortoise motor.  But that's OK since that turnout should already be at its desired position so no active motor drive is required!

Fine print.  You can't use the method of inserting red/green LEDs in series with the motor wires to indicate turnout position.  Instead hook up the LEDs to the internal Tortoise SPDT contacts (pins 2-6).

Fine print.  Since only one of the 6 relays can be on at a time with interlock mode, that means only 1 of the 3 Tortoises hooked to a module can be actively changing turnout position at any given time.  So if, for example, you are using the DCS Route function to automatically set the turnouts to a large number of Tortoises, you must insert a delay between turnout commands to Tortoises hooked up to one 6-relay module.

I wonder how hard it would be to separate the latching logic on that board so it worked in groups of two?  One might think that there would be some connection that might be severed to solve this problem neatly, maybe not?

gunrunnerjohn posted:

I wonder how hard it would be to separate the latching logic on that board so it worked in groups of two?  One might think that there would be some connection that might be severed to solve this problem neatly, maybe not?

That's an interesting idea.  If milwrd would read off the lettering/markings on the part below that might help answer feasibility.  If it turns out to be a $1 microcontroller chip, it ought to be re-programmable to re-define the interlock function to work in pairs rather than across all 6 relays.  In which case just replace/reprogram the chip without modifying the board wiring. OTOH, I can't imagine anyone going thru the effort.

IMO, if one must cut traces, patch wires onto small surface-mount parts, buy and solder tiny component(s), whatever, perhaps just a well to buy a genuine latching DPDT relay for $2 each and just wire up your own module.

Actually, this would be a candidate for an OSH Park board which would get the parts-only cost (DPDT latching relay, screw terminals, raw circuit board) to about $3-4 per Tortoise...but then we're back to procuring parts from different sellers, soldering, etc..  "Nothing is so easy as..."

I was thinking that if there was just a line between them...  I have no idea how the board works as I don't have one to look at.   I was not thinking of actually soldering on parts, etc. more along the lines of just hacking a trace on the board.

Well after a little more R&D per Stan's suggestion regarding the lemon-lemonade category. I hooked all three paired relays to switch machines and it worked great. Also as Stan pointed out if you're planning to incorporate the route function a delay will definitely be needed. On my last layout (the new one is under construction) I had a small yard and had the remote setup to throw two or three switches simultaneously, that would be a no go with one of these relays. However, if you had a bunch of them I believe you could make it work. So for about $3.50 per switch I think I'll get me a bunch.

Here is the info I got off the chip STC15W201S, below that 351-SOP16G. I had to use my cell phone camera as I couldn't find magnifier. Dang that was some small stuff.

A Big Thank You Stan!

So subject to some fine-print, you can control a Tortoise from an AIU SW port for about $3.50...no soldering required.  Nice!

Yes, thanks for identifying the mystery part.  That is indeed a programmable microcontroller chip made by STC Micro.  So I suppose the chip could be reprogrammed to change the Interlock mode to allow simultaneous, always active 3 Tortoise operation...but I can't see anyone going thru the bother!

I use a 24 volt Schrock model of this relay. Other than the latching mechanism and 2 coils it is quite ordinary as far as coil resistance and durability.  I run them stand alone an use them for block systems using a reed switch,an ordinary relay  and capacitor discharge."""Evev applying continous power to both coils I  could not burn them out     >>>Tthere is a little of the block system described in this thread for super streets            

https://ogrforum.com/t...-for-lemax-accessory

Dale H  

OK I know this is old but I was wondering why you need it to Lock if the AIU is dictating if it is to be on or not? If it needs to be a keep the switch in place (a memory thing) and or a power thing. You would be better off ordering a bunch of bistable relays and diodes. Making your own board Like this one, but with multiple relays.

However since you already have the board I suggest you NOT use interlock and USE the TR (Trigger). Keep in mind I am not a railroad guy and I don't know how that AIU works but I gather it is just a Single Pole Double Throw relay that is being used for each switches, with 1 (No or NC), 2 (No or NC), and IN (Common). In the Diagram below I am using a SPDT switch (The picture is a center off but you get the point?).  I can post a video of how you can use just two of the relays and still have use of the rest of the relays.

I know this is very late and I hope you already did this but I decided to post just in case you still want to use this board or if others need it.

Uhh... this is a four year old thread, I sure hope he solved the problem by now!

@gunrunnerjohn posted:

Uhh... this is a four year old thread, I sure hope he solved the problem by now!

Yeah that's why I said " I know this is very late and I hope you already did this but I decided to post just in case you still want to use this board or if others need it."

I also noticed that the OP Said the search continues" at one point. Was wondering what the final solution was.

And just out of curiosity was wondering wanting to find out if the AIU 1,2,and in are basically a SPDT relay?

@Mr. Mouthpear posted:

... I don't know how that AIU works but I gather it is just a Single Pole Double Throw relay that is being used for each switches, with 1 (No or NC), 2 (No or NC), and IN (Common).

Each AIU switch output indeed has 3 terminals.  However, internally there is a pair of relays for each switch output which implements momentary SPDT center-off functionality: (ON)-OFF-(ON).  The momentary time is exactly 0.5 seconds for each side.  This is why an external latching relay is needed for use with a Tortoise.

As you suggested, you can indeed buy a latching relay module rather than messing with an Interlock type relay module as the OP did.  But I think that was a lemon-lemonade situation where he already had the module in hand and was pondering how to put it to good use.

In addition to your AliExpress link (shown at right below), Azatrax has a variety of ready-to-go relay modules (example shown at left).   The nice thing about Azatrax is they make stuff for the train market so their instructions and application examples are spot on.

From what I can tell, most OGR guys want plug-and-play, no soldering, etc. ... and $10-$20 for a DPDT latching relay module with screw-terminals is not an issue.  But to your point, a DIY'er can indeed save a few bucks rolling their own.  As shown above you can get a DPDT latching relay for about $2 - only 2 Amps instead of 8 Amps but that's plenty for a Tortoise.  Then design/fabricate a bare circuit board to mount the relay, add some screw-terminal blocks, and you're off to the races!

I'm a bit surprised too to see this thread pop up after all this time. I am happy to report though with Stan's help it all works like a charm. As Stan points out, the AIU switch ports are all momentary delays and revert back to a neutral position after activation in either direction. The only issue I was initially concerned about was if the switch would stay in it's position when power was turned off. That however isn't a problem at all. When I installed the Tortoise machines I replaced the spring wires with thicker .040 wire (thank you Hot Water) so when power is cut there is more than enough tension left in the spring to keep the switch set in either position it was left in. Thanks again Stan.

@stan2004 posted:

Each AIU switch output indeed has 3 terminals.  However, internally there is a pair of relays for each switch output which implements momentary SPDT center-off functionality: (ON)-OFF-(ON).  The momentary time is exactly 0.5 seconds for each side.  This is why an external latching relay is needed for use with a Tortoise.

As you suggested, you can indeed buy a latching relay module rather than messing with an Interlock type relay module as the OP did.  But I think that was a lemon-lemonade situation where he already had the module in hand and was pondering how to put it to good use.

In addition to your AliExpress link (shown at right below), Azatrax has a variety of ready-to-go relay modules (example shown at left).   The nice thing about Azatrax is they make stuff for the train market so their instructions and application examples are spot on.

From what I can tell, most OGR guys want plug-and-play, no soldering, etc. ... and $10-$20 for a DPDT latching relay module with screw-terminals is not an issue.  But to your point, a DIY'er can indeed save a few bucks rolling their own.  As shown above you can get a DPDT latching relay for about $2 - only 2 Amps instead of 8 Amps but that's plenty for a Tortoise.  Then design/fabricate a bare circuit board to mount the relay, add some screw-terminal blocks, and you're off to the races!

See now it all makes more sense. I like the smaller  Azatrax board you linked. Very nice. I saw those a while back when I purchased the ones from Aliexpress. I went with that one because I like that it can be mounted easily on din rail.  I have yet to see a railroad setup that has din rail for it mounting components LOL. I did order 20 of the relays themselves to make my own. Came out way cheaper. Only spent $15 including shipping.

@Mr. Mouthpear posted:

...I did order 20 of the relays themselves to make my own. Came out way cheaper. Only spent $15 including shipping.

So did you design/fabricate a bare PCB?  If so did you do this thru OshPark and/or prepare the Gerbers in a way that can be shared for easier ordering by others here on OGR that might be interested?  This DPDT latching relay topic pops up every so often.

Separately, and speaking of mounting, what I really like are your Wago-like splitters with DUAL conductors...and color coded at that!   I know Wago has DIN rail adapters for the ubiquitous orange-lever style but they are bulky and cost a fortune.  Instead, it seems most guys just resort to hanging them in mid-air, trying to glue them under the layout, etc..  Do you (or anyone for that matter) know the "story" behind what appears to be a knock-off of the Wago design?  I like the two screw mounting holes.  I would have thought Wago would have a patent and/or introduced the dual conductor version first... or maybe I just missed it.

Found some:Ebay #

@stan2004 posted:

So did you design/fabricate a bare PCB?  If so did you do this thru OshPark and/or prepare the Gerbers in a way that can be shared for easier ordering by others here on OGR that might be interested?  This DPDT latching relay topic pops up every so often.

Separately, and speaking of mounting, what I really like are your Wago-like splitters with DUAL conductors...and color coded at that!   I know Wago has DIN rail adapters for the ubiquitous orange-lever style but they are bulky and cost a fortune.  Instead, it seems most guys just resort to hanging them in mid-air, trying to glue them under the layout, etc..  Do you (or anyone for that matter) know the "story" behind what appears to be a knock-off of the Wago design?  I like the two screw mounting holes.  I would have thought Wago would have a patent and/or introduced the dual conductor version first... or maybe I just missed it.

@John H posted:

Found some:Ebay #

124219900801

About $17 for ten.

Do NOT get those! I repeat do NOT get those! They are not good. They split in the center when you lift more than one. It might be ok if you have single wire or don't mind splitting the red and black paired wire. I do mind.  When it spreads open you can't put the wires in. If you want to quickly take out all the wires, you can't.

The screw hole is way too small and does not go flush to the bottom and can break off, if accidentally applied too much pressure, which isn't much.

Get these. They don't split.

The mounting holes are attached on two sides and go all the way down flush to the bottom.  Much more beefy.

They are uniform. Meaning the 2 IN 4 OUT holes line up with the holes on the 2 IN 6 OUT. So if you wanted to screw two of them together, back to back, you can. (Even if you got two of the junk ones that are the same you can't. The backs are not flat.) I screwed the 2 way connector to a 2 IN 6 OUT, back to back.

Here I have a bunch of then and one of the crappy ones, all setup on my latching relay demo for my safety door return up then back down circuits for chicken coops. Left to right. 3PDT relay very easy to make latching. Center is the Bistable one I ordered and mentioned before. Right is a regular ole DPDT relay using a diode you can make it latch. I am looking into adapting that last one for this thread, using the board mentioned here and the same board in the background in the pictures. The gears in my head, are grinding.

As for the making of the relay board. Nope, no schematics or PCB layout. I just slapped them on a perfboard and started soldering. Made sure the diodes were correct on the first one and pressed on. I wanted to take pix but can't find then. They are in a safe place for when I need them. Just can't remember where that safe place is. LOL.

I set them aside when I figured out how to make a latching relay with just a diode. Like I said I want to try and figure a way to make it unlatch so it can be used for this. The latching part is easy (I think, haven't tested yet), it's the unlatching that I haven't figured out yet. I'll post if and when I got it figured out.

What good is it if I didn't post where to get the better ones. LOL.

@stan2004 posted:

So did you design/fabricate a bare PCB?  If so did you do this thru OshPark and/or prepare the Gerbers in a way that can be shared for easier ordering by others here on OGR that might be interested?  This DPDT latching relay topic pops up every so often.

Separately, and speaking of mounting, what I really like are your Wago-like splitters with DUAL conductors...and color coded at that!   I know Wago has DIN rail adapters for the ubiquitous orange-lever style but they are bulky and cost a fortune.  Instead, it seems most guys just resort to hanging them in mid-air, trying to glue them under the layout, etc..  Do you (or anyone for that matter) know the "story" behind what appears to be a knock-off of the Wago design?  I like the two screw mounting holes.  I would have thought Wago would have a patent and/or introduced the dual conductor version first... or maybe I just missed it.

How to mount? They sell little orange mounting clips for the Wago style 2,3,4,5,6,.... snap connectors. You can see them in this video I made to show two Photocell relay modules used to operate a linear actuator. They tend to pop off with slight pressure, so I super glued them. Now I can screw them down AND pry open the levers without it popping off.

https://youtu.be/gNbgvKYlEBc

Talk about night and day with respect to the mounting holes!  I know which ones I'll be getting.   I also see that the left style has voltmeter probe access holes which can be handy.

Separately do you have a link to the "little orange mounting clips" for the Wago style connectors?  I see them in your video but nothing useful came up when I searched on that terminology!

Anyway, I didn't mean to derail the conversation from the topic at hand (latching relays).  I am making reference to this side discussion in a contemporaneous Wago connector thread where perhaps we should migrate.

Getting back to the topic of relays.  As I stated earlier, most guys would rather buy an assembled and tested DPDT latching relay module vs. save a few bucks with a DIY soldering extravaganza.  But this being a discussion forum, there's an OGR thread somewhere showing how to wire up the equivalent of a DPDT latching dual-coil relay using multi-SPDT $1/relay modules.  IIRC it took 3 SPDT relays... and of course unlike a genuine latching relay it returns to the "reset" position when power is removed.  So maybe it's an audience of one but I'd like to see what you have in mind using a diode to "make" a dual-coil DPDT latching relay.

@stan2004 posted:

Separately do you have a link to the "little orange mounting clips" for the Wago style connectors?  I see them in your video but nothing useful came up when I searched on that terminology!

Anyway, I didn't mean to derail the conversation from the topic at hand (latching relays).  I am making reference to this side discussion in a contemporaneous Wago connector thread where perhaps we should migrate.

Getting back to the topic of relays.  As I stated earlier, most guys would rather buy an assembled and tested DPDT latching relay module vs. save a few bucks with a DIY soldering extravaganza.  But this being a discussion forum, there's an OGR thread somewhere showing how to wire up the equivalent of a DPDT latching dual-coil relay using multi-SPDT $1/relay modules.  IIRC it took 3 SPDT relays... and of course unlike a genuine latching relay it returns to the "reset" position when power is removed.  So maybe it's an audience of one but I'd like to see what you have in mind using a diode to "make" a dual-coil DPDT latching relay.

I posted in the other tread but just to follow up here. The Mounting clips.

@stan2004 posted:

Getting back to the topic of relays.  As I stated earlier, most guys would rather buy an assembled and tested DPDT latching relay module vs. save a few bucks with a DIY soldering extravaganza.  But this being a discussion forum, there's an OGR thread somewhere showing how to wire up the equivalent of a DPDT latching dual-coil relay using multi-SPDT $1/relay modules.  IIRC it took 3 SPDT relays... and of course unlike a genuine latching relay it returns to the "reset" position when power is removed.  So maybe it's an audience of one but I'd like to see what you have in mind using a diode to "make" a dual-coil DPDT latching relay.

There are several ways to do a latching relay with a single button press. These are just two.