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Chris Savage
02-29-2012, 10:13 PM
Parallax has a new product coming out based on feedback and requests from our customers. If you ever hada need to control 1 or 2 devices where a relay was required, the Dual Relay Board Kit is just what you need. The kit comes complete with the hardware shown below. Soldering required, but all through hole parts are used.

90154

Once assembled the Dual Relay Board requires a 12V power supply for the relays and a signal and common ground to your BASIC Stamp Module, Propeller chip or other microcontroller output pin for each relay.

90155

12V power for the relays is provided via the terminal block on the top of the board in the above photo. The LEDs indicate a relay is active (ON). The 2x3 header on the left provides ground and signal access to trigger each relay and can accept a standard servo cable such as those commonly used with many of our other accessories. The terminal block at the bottom provides COM, NO and NC connections to each Omron relay, capable of switching 12A @ 250VAC.

The drivers for the relays are simple 2N3904 transistors and can be activated by 3.3V and 5V. Diodes protect the transistors from back-emf and the board includes mounting holes. The dual relay board can also be controlled directly from the output of many sensors, such as our PIR sensor (#910-28027) or (#555-28027). If you have any questions, please reply. These should be available in mid-March.

davejames
02-29-2012, 10:35 PM
Mr. Savage - is that 12A really switching current or is it carry current?

Chris Savage
02-29-2012, 10:44 PM
Dave,

The datasheet (http://www.parallax.com/Portals/0/Downloads/docs/prod/compshop/400-00052Datasheet.pdf) for the 12A Omron Relay (http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/relay/List/0/SortField/4/ProductID/656/Default.aspx) can be found on the product page on our website. See the section under contact ratings. Of course, when switching high-currect devices the power source should be fused before the relay board. =)

davejames
02-29-2012, 11:13 PM
...well, I'll be.

The spec sheet strongly implies that, under certain conditions, the relay can switch 12A. And it's not even a mercury-wetted type.

Impressive.

erco
02-29-2012, 11:30 PM
RELAYS?

Kinda old school,huh?

I'm diggin' it! :)

Ttailspin
02-29-2012, 11:52 PM
...The 2x3 header on the left provides ground and signal access to trigger each relay and can accept a standard servo cable such as those commonly used with many of our other accessories.

What happens if I plug this 2X3 header into the servo header on the Prop Proto board or the PPDB?.
What happens to the five volts? or V_ext if I have that hooked up?.


-Tommy

Ken Gracey
03-01-2012, 03:52 AM
Chris, excellent work. I've got one of these kits in hand and hope to build it this weekend. For many years customers have asked us for a simple solution so they can turn a light bulb on or off from their microcontroller. Instead of giving them what they want, we gave them all kinds of complex, expensive and sometimes co-processor solutions.

Finally, Chris delivers a simple DIY solution. Thank you Chris! If I had time I'd be replacing the darned Tekmar control system in my home's boiler.

Ken Gracey

Roy Eltham
03-01-2012, 04:03 AM
Nice little handy board.

ajward
03-01-2012, 10:14 AM
RELAYS?

Kinda old school,huh?

I'm diggin' it! :)

Erco... now =this= is old school!

90169

I've always wanted one of these for some project.
(Yeah... probably watched too many old time monster movies.)

PJ Allen
03-01-2012, 12:14 PM
I know that I've recommended similar kits/boards but such a thing was always just a bridge too far ("it costs too much", "I can't solder", "I need one, not two... I need two, not one... Those are spdt, I need spst..."

Martin_H
03-01-2012, 01:33 PM
Amanda, hook a servo up to that knife switch and you'll have something.

bill190
03-01-2012, 02:58 PM
I like mechanical relays for their ability to totally isolate electrical circuits.

For example all the wiring in a home or business for a security system can act as an antenna. Or a nearby lightning strike can induce a high voltage in that wiring. If you have a transistor on the end of that wiring, Zappp! But if you isolate the wiring from the transistor using a good old fashioned mechanical relay, it becomes a tough reliable system.

The most "cool" relay I have ever seen is a stepper relay...

90171

Chris Savage
03-01-2012, 03:13 PM
What happens if I plug this 2X3 header into the servo header on the Prop Proto board or the PPDB?.
What happens to the five volts? or V_ext if I have that hooked up?.
-Tommy

Tommy,

Since the relays require 12V to power them and that comes from the terminal block, the center pin on the servo headers is not connected. This frees you to connect the board to a BoE, PDB, PPDB, or any board that has a servo header and connects the ground and signal. This is the same way our HB-25 works, not connecting the servo voltage pin, since it isn't needed by the host controller.

The 12V relays do work with a little less voltage (see the datasheet on our website), and in a demo here on my bench I have provided power from the BoE VIN to the terminal block on the Relay Board. I also connected two servo conection cables from the BoE servo headers to the headers on the relay board (see red arrows in picture). You might notice I didn't connected the ground wire for power in this case since it is common with the BoE and the servo cables are already connecting ground.

90172

The resistor chosen on the input of the driver transistors was chosen to provide enough base drive current from 3.3V or 5V systems based on the gain of the transistor and the current required to engage the relay. As Ken said, this is an easy solution to turn on a 120VAC lamp, motor, pump, etc. And of course you have two relays, so you can control two different devices while providing isolation. I hope this helps.

Chris Savage
03-01-2012, 03:15 PM
I know that I've recommended similar kits/boards but such a thing was always just a bridge too far ("it costs too much", "I can't solder", "I need one, not two... I need two, not one... Those are spdt, I need spst..."

As a kit we'll keep the cost on this as low as we can.

Ttailspin
03-01-2012, 04:13 PM
Since the relays require 12V to power them and that comes from the terminal block, the center pin on the servo headers is not connected. This frees you to connect the board to a BoE, PDB, PPDB, or any board that has a servo header and connects the ground and signal. This is the same way our HB-25 works, not connecting the servo voltage pin, since it isn't needed by the host controller.

I figured it was as simple as that, but I just wanted to be sure,
I almost had some trouble with the QTI sensor wiring harness. Good thing I double check my wiring...:)


-Tommy

Chris Savage
03-01-2012, 04:26 PM
Tommy,

Everyone should always feel free to ask question on products, especially when, as in this situation, the only information is available right here in the thread about the coming product. We will sometimes use feedback given at this stage to make minor changes to a product, however in this case I have sent a few samples out for direct feedback because it is such a simple product. All questions and feedback are appreciated.

Shawn Lowe
03-01-2012, 05:46 PM
Looks good! Gonna have to get me one or two!

PJ Allen
03-01-2012, 05:47 PM
The picture in #13 puts it in perspective - it's a big ol' honker.

PV Jr. - I love mine, indispensable. Definitely get a base mount (a 308 or 312) for it.

davejames
03-01-2012, 07:00 PM
The picture in #13 puts it in perspective - it's a big ol' honker.

Holy moly!!! I didn't read through the dimension info and missed the physical size.

Now I get why it's spec'ed for mulitple amps switching current...

jlumens
03-01-2012, 09:34 PM
This might be a dumb question because I am really new to all this. Also, I have never posted to the forums before so forgive me if this question is inappropriate.
How will this compare to the EFX-TEK RC-4 Relay Control Board?

Chris Savage
03-01-2012, 10:28 PM
Julia,

Your question is completely welcome and valid. The RC-4 uses Solid State Relays, whereas the Dual Relay Board Kit uses mechanical relays. Solid State Relays are great for switching AC loads especially when you want to minimize noise in the system. Some SSRs such as the Crydom relays used with the RC-4 have zero-crossing detectors to make this possible. However SSR relays are either AC or DC in their configuration and cannot switch both AC/DC circuits whereas a mechanical relay can. I'm not sure if there are SSRs for the RC-4 which can handle DC, but I doubt it. I believe the SSR current rating is also lower than the mechanical relays used on the Dual Relay Board Kit. If you have any additional questions, feel free to ask.

xanadu
03-01-2012, 10:39 PM
Mechanical relays are irreplaceable. I have been scouting premade relay boards and this one looks great put me down for three.

xanadu
03-01-2012, 10:44 PM
Could you tell me the mounting hole dimensions for the board?

doggiedoc
03-01-2012, 11:23 PM
@Chris - very nice. Did I over look the release date or was it not mentioned? I'm going to need a few of those.

P

jlumens
03-01-2012, 11:50 PM
9018490185I went to the EFX-TEK web site and downloaded cut sheets for both the AC and the DC relays that they recommend. The AC relays are rated at 240 VAC at 3A and the DC relays are rated at 60 VDC at 3A. If I can figure out how to attach the cut sheets to this response I will. I marked the specific model of each that is recommended.

Chris Savage
03-02-2012, 12:04 AM
Could you tell me the mounting hole dimensions for the board?

The mounting hole centers are 1.5" x 2.0"

Circuitsoft
03-02-2012, 12:06 AM
For people who want a smaller automotive-environment version, is there any chance of making a relay board with a Panasonic CT512 relay?

Chris Savage
03-02-2012, 12:06 AM
@Chris - very nice. Did I over look the release date or was it not mentioned? I'm going to need a few of those.

P

Doc, very first post. Should be middle to end of this month. I think it mainly depends on how long to get the boards.

john_s
03-02-2012, 03:26 AM
I hope there's some space left to consider rev.b with some smart interfacing as in Communication Module (http://www.youtube.com/watch?v=zOLoL7W5F_M&NR=1&feature=endscreen)

Chris Savage
03-02-2012, 07:09 AM
PV Jr. - I love mine, indispensable. Definitely get a base mount (a 308 or 312) for it.

PJ,

I do have a base for it...sort of...I have the 335 Magnetic Base which I was going to use to attach it to my metal bench in the garage, but this unit is so handy for smaller, lighter work that I prefer to keep it inside, so I haven't even taken the 335 out of the packaging. And the PV Jr. hasn't yet needed a base for what I use it for.

90194

When I need something bigger I use the Model 315 PCB Holder (http://www.savagecircuits.com/forums/content.php?283-PanaViseŽ-Model-315-PCB-Holder), equipped with a custom base by Matt Gilliland (http://www.flickr.com/photos/savagecircuits/6242110919/).

And speaking of the PV Jr. Ken Gracey has assembled 18 soldering stations for the Parallax Expo (http://www.parallax.com/expo). Each station includes a PV Jr. I'll leave it to Ken to post the pictures of the kits since I do not have them. =)

UPDATE: Ken sent me the pictures of the PV Jr./Hakko Soldering Stations that will be set up for use at the Parallax Expo.
9021090211

xanadu
03-03-2012, 06:13 PM
Thanks for that info, I have a project using relays that will be done around the same time so I hope to use yours.

Is there going to be an optocoupler board?

John R.
03-04-2012, 04:21 PM
I was fortunate enough to be sent an evaluation kit on the Dual Relay Board Kit. The documentation was very clear on assembly instruction, and included a good description on the theory of operation, and how to calculate the resistor values for the transistor.

The board is very compact, and if the suggested order of assembly is not followed, it will be a challenge to place the smaller components.

I will be putting the relay board inside an outlet box, and using to control a heater and pump for an aquarium, or using it to turn on a shop vac, either via I/R or R/F control (and/or current draw of a sander).

Very nice kit!

doggiedoc
03-20-2012, 11:20 AM
John - I too was fortunate enough to receive an evaluation sample of the kit. I will assemble it as soon as time allows, but I can see that the board is well made and and the components are top quality. I have several uses in mind - and will report back on my progress after assembly!

Paul

tonyp12
03-21-2012, 05:33 AM
I'm more in to solid state.
Would there be a demand for this $9 (populated) board?
Dual 8Amp continues.

With a rather low Vds-max of 20V would be good for automotive mostly or other 12v systems.

Vgs is extremely low and mosfet will be fully on at 3v for direct Prop pin drive.
But don't need a MCU to work, you can use the pull up/down pads for phototransistor etc.

bsnut
03-21-2012, 07:43 AM
Welcome to the forums Julia.

That's ok. The difference between EFX-TEK's RC-4 and the Parallax relay kit is, that the RC-4 is controlled by serial commands from the host controller and the relay kit isn't. Another difference with the RC-4 is, that it uses 4 Crydom Solidstate relays and the Parallax kit uses two mechanical relays that have Normally Open and Normally Close contacts to connect to and are controlled by High or Low (PBasic) commands from your controller.

BTW, the RC-4 used to be a product that was sold by Parallax about 6yrs ago and now is sold by EFX-TEK.

Chris Savage
03-21-2012, 04:28 PM
We have not ruled out releasing a Dual SSR Relay Board, however the focus is currently on the mechanical unit as it serves an educational role and is generally more flexible in application.

Loopy Byteloose
03-21-2012, 04:55 PM
After going back and forth, I have come to prefer the mechanical relays over solid-state. The primary advantage of solid-state is that they may offer direct connection from 3v or more - where as mechanical relays often require a boost to 12VDC in order to work.

That boost implies a more complex power supply for mechanical, but there are a lot of dual switcher power supplies available with +5 and +12. And many of the Propeller Boards with accept a +12VDC as raw power, then step it down as required.

There are great advantages in the mechanical relay in terms of adaptiblity. Both AC and DC can be used. And most relays are DPDT; whereas solid-state are often SPST.

Eventually, one has to become knowledgible of both - but the mechanical is a better item for the rank beginner as a first buy.

BTW, it used to be that the solid-state relays actually took up more space than the mechanical and often ran hotter - but they were silent. Currently, everything is changing - so it is hard to generalize. I still have several 'hockey puck' solid-state relay, but there is NO REASON that you much buy such big clunkers if space is short.

Furthermore, I generally run 12amp relays eventhough I might be using only 3 or 4 amps. That headroom just means that the relays last longer and less problems arrise.

erco
03-21-2012, 09:52 PM
the focus is currently on the mechanical unit as it serves an educational role and is generally more flexible in application.

+1, my relay brother!

Chris Savage
03-22-2012, 05:31 PM
Appeciated. If it weren't for the educational theme I would have used a FET and SMD components to switch the relay.

tonyp12
03-22-2012, 05:56 PM
Relays with DPDT,high-side, A/C etc. a good thing.
But not being able to do PWM to dim a light etc., only a mosfet can do that.

Chris Savage
03-23-2012, 03:33 PM
Relays with DPDT,high-side, A/C etc. a good thing.
But not being able to do PWM to dim a light etc., only a mosfet can do that.

A MOSFET will only work on a DC light. For AC you would need a TRIAC-based circuit with a delay and zero-crossing detection. Still, compared with simply turning high-power devices on/off, PWM control of such devices is less common.

tonyp12
03-23-2012, 05:25 PM
Two MOSFETs with their source pins connected together as in the Phidgets SSR module with the NEC/CEL SSR IC will also drive AC loads
This works since all MOSFETs have a substrate diode that always conducts current in the reverse direction
And that is what I will do with the second version of my relay board.

mojorizing
03-28-2012, 11:49 AM
Hello Chris,

Will the Dual Relay Board Kits be available for purchase soon?

Thanks,
Kevin

Chris Savage
03-28-2012, 11:09 PM
They should be available some time in April.

doggiedoc
04-05-2012, 10:21 PM
Chris -
Thanks for letting me evaluate a kit. I've just finished assembling the kit and it was a very strait forward process. The silkscreening on the board is very clear and I had no trouble with parts placement at all. Soldering skill is above beginner but I would think the most could handle it fine. Board quality is fantastic. Exactly what I've come to expect from Parallax.

I look forward to hooking it up and testing it now. More comments will follow.

Paul

vanmunch
04-20-2012, 07:28 PM
Keeping my eye out for these to be on the new products page...

Chris Savage
04-20-2012, 09:19 PM
We should have these on our website Monday or Tuesday.

RS_Jim
04-24-2012, 01:22 PM
Chris,
Did they make it up to .com yet? I could not find it this am. Would like to pair this with a spinnernet to provide remote power control for a pair of wireless printers.
Jim

Chris Savage
04-25-2012, 04:49 PM
Jim,

Had to retake the photos for the documentation. I am sending everything in today (again). I have the same camera (Nikon D80) but fail to take the same level of quality pictures, so yesterday while in the office I decided to get a crash course in D80 product photography. Once I send everthing in it should be up in a day or so. Sorry for failing to deliver on my original date. I took pictures with two different cameras and they were too dark and grainy.

Leon
04-25-2012, 04:56 PM
I have a Nikon D80, as well. I'm ashamed of some of the photos I take with it, mainly because I can't be bothered to set up the tripod and get the lighting correct.

Chris Savage
04-25-2012, 05:12 PM
Well I never got good photos from my Cell Phone camera. But it is a little embarassing when pictures from my Sony Hanycam HD Video Camera come out better than the Nikon D80, which cost three times as much. It seems I was not properly setting up several settings and of course, Auto Mode can't fix everything. Oh, and I have a Tripod, but I still have to use a remote because it is not real high quality, so pushing the button causes it to shake too long for the picture to come out. Maybe sharing this information will help others in this situation. I sought help from someone who did know what they were doing.

Leon
04-25-2012, 06:02 PM
What I really need for photographing my electronic creations is a light tent (cheap) and a couple of suitable lamps (quite expensive). I have a home-made IR remote using a little PIC, but I usually use the self-timer if I have the camera on a tripod, to avoid camera shake. My tripod is a very good Manfrotto one, anyway.

RobotWorkshop
04-25-2012, 06:16 PM
Trying to get the lighting just right can be a pain. If the item is small you can get great results by using something like this:

http://www.ebay.com/itm/Elmo-EV-400AF-Color-Video-Presenter-Document-Camera-/200749958487

You can often pickup used units pretty cheap. I don't use the built-in camera but have found that it is often worth using just for the controlled lighting. This model also can light from underneath as well.

Chris Savage
04-25-2012, 10:19 PM
I definitely need something like that. I also saw a kind of product tent camera setup at ThinkGeek.com. Anyway, the new photos are done and I have sent the docs to our Tech Support Dept. for review. As soon as they approve them they go to our editor and we can then put them up on the web with the product. Trying for Friday on this. I will keep you updated. Thanks for the feedback everyone (and the patience)!

RS_Jim
05-02-2012, 03:21 PM
Any word on when this will hit?

Chris Savage
05-02-2012, 07:25 PM
Jim,

I was in Rocklin yesterday and talked to out Tech Support Dept. who still has the product in review. As soon as they're done we'll be about 2 days from selling them. I apologize for the delay.

RS_Jim
05-02-2012, 08:23 PM
Thanks Chris.
Jim

Chris Savage
05-10-2012, 07:57 PM
Okay, the kit has been through all the hoops and should be online for sale by this afternoon or tomorrow morning at the latest. Our WebDev team is getting things up as quickly as possible. As for the previous delays, we're working on improving our process to avoid hang-ups in the future.

Vern
05-10-2012, 09:38 PM
Thanks! As soon as they hit I'll be ordering one.

Chris Savage
05-11-2012, 06:12 PM
And...they're up! :thumb:

Get yours now...the Dual Relay Board Kit (http://www.parallax.com/tabid/768/ProductID/843/Default.aspx)for $19.99! Woot!

henny
09-12-2013, 02:57 PM
Hi! I've just bought one of this kits from RS Components and have been very impressed with it... However, I need to modify it so that it's switched by grounding an input, rather than adding 3.3 -> 5V onto a pin, as that's the only signal that the kit I've got which will be triggering it can give...

I've modified the circuit diagram (in paint, please forgive me!) to use a PNP transistor instead of an NPN (a pair of 2N3906) and reversed the + and - inputs and the polarity of both the LEDs and the Diodes... (attached to this post)

I know that this will also make pins 5 and 6 (and the mounting points!) be 12V instead of ground, but as long as I don't mind that (it'll be mounted in a box, suspended on plastic mounts) and as long as I connect the return from my switching device straight back to the ground of the power supply, I think I should be OK...

In your opinion, will this work, or am I missing something? (it's been a long while since I did any electronics!)

Anyway, this is a brilliant kit that I just keep coming up with uses for since I bought one... :)

Bean
09-12-2013, 03:10 PM
Just be aware that the relay will be on if the inputs are below +12V. Not just when the input is ground.
In other words, if the input goes from +5 to ground, then the relay will be on all the time.


P.S. Welcome to the forums

Bean

henny
09-12-2013, 04:42 PM
Just be aware that the relay will be on if the inputs are below +12V. Not just when the input is ground.
In other words, if the input goes from +5 to ground, then the relay will be on all the time.


P.S. Welcome to the forums

Bean

Thanks Bean, sounds like that's probably not a good solution then...

So, if you were going to do it, how would you do it?

Cheers!

Ian...

Chris Savage
09-12-2013, 05:21 PM
Welcome to the forums. It would help to know what your control signal is that you need to drive the relays. You said it needed to be low instead of high, but what is the voltage range of this control signal? Is it open-collector?

henny
09-12-2013, 05:37 PM
Welcome to the forums. It would help to know what your control signal is that you need to drive the relays. You said it needed to be low instead of high, but what is the voltage range of this control signal? Is it open-collector?

D'Oh! Yeah, it's an open collector, sorry, should have put that initially! :innocent:

Thanks for the welcomes... :cool:

Bean
09-12-2013, 05:56 PM
If it is open collector, then it should work as you have it...

Bean

Chris Savage
09-12-2013, 06:01 PM
If it is open collector, then it should work as you have it...

Bean

Not as the board comes, because the signal line has to go high to turn the relay on. Since he has an open-collector output I was thinking that if it can handle the current, it could switch the relay in place of the on-board transistor, but I don't know the nature of this open-collector signal.

To the OP, what is the driver of this signal? Is it a FET and if so, how much current can it sink? What is the device that you're using to drive the relay board?

skylight
09-12-2013, 08:45 PM
Could you use an inverter on the input?

Loopy Byteloose
09-13-2013, 08:31 AM
I suppose you could put an inverter, such as a 74HC04 chip on the input to reverse a relay's behavior. But you can do this inversion in code in the Propeller or BasicStamp by just swapping High and Low output in code. Using such a chip requires a power source to it.. that can be a problem.

There are safety issues with reversing the signal from High equal to coil on, to Low equals coil on. What happens when you first power up the whole system including the relay board? This needs to be looked at as signals may default in a way that something is running that is unexpected.

It would be odd to have a microcontroller provide an open-collector output. That role is is regularly a buffer chip or a driver chip of some sort.

There are open-collector buffer chips, such as the 74HC07 that do this AND the open-collector side will accept a much higher voltage (like a +12 relay) and connect it to ground. So you can jump from a 3.3 volt output to activating a +12 relay in one-step.

Open-collectors are a good thing for robotics. It pays to learn to use them, not just with relays.. but with other devices that desire a voltage jump.

http://en.wikipedia.org/wiki/Open_collector

henny
09-13-2013, 10:43 AM
Hi!

I have a slight issue in that the open collector is within a mixing desk, (not a microprocessor - so I can't alter the code!) and I don't have the exact spec for it! I'm pretty sure that trying to use it to drive the relay directly would be a very bad thing to do, hence trying to modify this circuit to use a PNP transistor switched to ground, rather than an NPN which needs the signal to go high... :smile:

Bean? Did you mean that it should work with the modifications I posted a diagram of?

Thanks all for your help, it's appreciated... :)

Bean
09-13-2013, 11:37 AM
Hi!
Bean? Did you mean that it should work with the modifications I posted a diagram of?


Yes, I would think it would work WITH your modifications. As long as the open-collector input does not sink any current when it is off.

But it would have been much easier to just use the original circuit and add a pull-up resistor to the input.
This would turn the relay on when there is no input, and the relay would be off when the input is active. But since the relay has both NC and NO connection, just simply reverse them.

Bean

Loopy Byteloose
09-13-2013, 12:08 PM
Bean's suggestion of a pull-up resistor is the best of all.

But for what it is worth....

The primary issues with an unknown specification open-collector are the usual -- volt limit and current tolerance.

Generally, the open-collector is just a transistor (or it would be called an open-drain if it was a MOSfet). It is nearly impossible to build a transistor that won't tolerate 25 volts or less in open-collector switching.

The issue of maximum acceptable current is much more critical.

Does one dare to guess?

I suspect 20ma is no problem and limits might be approached at 40ma if it is an IC. (Take a look at the specs for the 74LS07 for comparison http://www.ti.com/lit/ds/symlink/sn74ls07.pdf). Since driving a 12amp relay needs a bit of speed to engage, I suspect that 60ma is barelly enough to properly do the job. Many 12amp relays need more than that at 12 voil coils, a lot more.

What to do? Consider a Darlington transistor configuration (or its compliment) to do the inversion and to handle the extra current. I suspect the open collector in place can provide the first stage and if you need an NPN second stage a 2N2222 will handle 500ma easily. (For NPN, use its compliment the wN2907). Amplification would be a lot higher. The trade off is Darlingtons operate with a bit of heat.

henny
09-13-2013, 05:36 PM
Well, I did it, (as per the diagram I posted) and can confirm that it does work... :)

Thanks to all who have answered, it's been much appreciated... :) (and I'll definately be buying more of these kits, as the build quality is top notch...)

Loopy Byteloose
09-14-2013, 10:36 AM
I suspect it is best to use the board unmodified and apply Bean's solution of a pull-up resistor if at all possible.

Modified boards may migrate into the hands of users that think they are unmodified and that the documentation is enough to work with them. Confusion and likely destruction of something might follow.

Chris Savage
09-16-2013, 03:30 PM
Yes, I would think it would work WITH your modifications. As long as the open-collector input does not sink any current when it is off. But it would have been much easier to just use the original circuit and add a pull-up resistor to the input.
This would turn the relay on when there is no input, and the relay would be off when the input is active. But since the relay has both NC and NO connection, just simply reverse them.

Bean

I just wanted to point out, in case the OP wasn't aware, that in doing so the relay will be energized when inactive and only de-energized when you activate it. So when the circuit being switched is off you'll be drawing ~80 mA of current. This should only matter if the circuit is battery powered or depending on duty cycle of the switching.

Loopy Byteloose
09-17-2013, 11:30 AM
While relays are absolutely brilliant devices for isolation and jumps to higher voltages and to and from DC to/from AC....
Latcing relays can resolve that remaining bugaboo of needing a coil to be consistently powered in one position.

In nearly all cases, the latching relay is the low power cousin to the conventional relay.... very very environmentally friendly.

But there are some things to notice.
A. they require pulses.
B. the more powerful ones require two input lines -- one for each state. (This is actually a good thing as you don't need to have feedback confirm which state you are in.)