Dual latch Relay Circuit Setup

[DrDiettrich]

Continue with the 330R. Current is only drawn as long as the relays are triggered.

It may be possible to drive the relays from the Arduino 5V, but only with big caps (>=1000µF) added, or you risk controller resets or other malfunction. But if you already have a 5V supply, you can power both the Arduino and relays from that supply.

[Mikie_lomas]

each coil uses 150mA
if you use the Arduino power, you may have a dip in voltage.
however, there is a away to trickle charge a cap to use that for the power dump to the coil.
you cannot change state before it charges, and you cannot energize two at the same time  unless you size the caps properly.

Thanks for the reply. But I am not exactly sure what you mean.

The option is to have latching relays all around my house, which is powered through cabling in the wall.

I had a thought that I could have a main 15v 3-4A power supply fed throughout the house via phone cabling (to account for voltage drop), it should drop down to an acceptable 6-12 V by the time it hits the arduinos. I would then use the regulated 5v supply to latch the relays. If I cant power from the nanos, i basically have two options.

Option 1: Input wall cavity power sockets and then use AC - DC 5v 1A USB sockets which I plug into the nanos and then a separate 5v supply for the relays

or

Option 2: Send a higher voltage through the phone cabling all around the house and then attempt to regulate the voltage down to 5v at the end for the relay...Not sure on that one.

Any guidance would be very much appreciated. thank you in advance

Continue with the 330R. Current is only drawn as long as the relays are triggered.

It may be possible to drive the relays from the Arduino 5V, but only with big caps (>=1000µF) added, or you risk controller resets or other malfunction. But if you already have a 5V supply, you can power both the Arduino and relays from that supply.

Does this mean I can do either the main external power supply for everything through phone cabling or a single 5v in each wall as said above and then I activate a plus and a negative on a board such as this:

http://www.ebay.com.au/itm/Protoboard-Plus-Tiny-Premium-DIY-Protoboard-Perfboard-for-Arduino-AVR-PIC-/331627685381?hash=item4d368ce605:g:m5YAAOSwT6pVzF6S

and this would be an acceptable method of powering both units?

Thankyou for your time

[Mikie_lomas]

I just looked up voltage drops and although 15v 3-4A is quite considerable...

5v at 20ma is very minimal indeed. Maybe it would be better to have a main controlling arduino that sends signals through cat 6.

If I were to feed the main arduino 7-12 volts, but then send the reset and set , arduino 5v and power supply ground out on 4 different cat 6 inner cables. Would this work by any chance?

[dlloyd]

I just followed the code you provided originally and there was a 40 - 1000 ms delay change. So i assumed this was what you meant.

The 40ms is the pulse duration. The 1000ms is the timing between Set and Reset. When looking at the LEDs in the test circuit, the Set LED will give a very quick blink, then 1 second later the Reset LED will quickly blink, then this repeats forever.

So basically, the control signal (quick pulse) toggles back and forth from the Set pin to the Reset pin. The relay contacts do not pulse. They will close continuously for about 1 second, then open continuously for 1 second, and repeat like this forever.

I have removed the revised circuit from within the area entitled test relay circuit and replace that with the relay. This allow me to latch the relay either way, it kept its state after power off!!!

Yep. That's why its called a "latching relay". It has memory. This is the main advantage of this type of relay ... it only takes minimum 30ms of power to the coil to change the status of the contacts. In the test code, the relay coil draws no power whatsoever 96% of the time.

each coil uses 150mA
if you use the Arduino power, you may have a dip in voltage.

Note that Set and Reset are never activated at the same time. So 150mA is the peak current, but only for the pulse duration (30ms minimum). Most of the time the coil is disconnected. A capacitor could help if the supply can't handle a 150mA impulse, but I doubt this would be a problem.

[dlloyd]

The option is to have latching relays all around my house, which is powered through cabling in the wall.

How many relays? Note that you'll need 2 digital outputs per relay.

Can the relays be Set or Reset sequentially? If so, all that's needed is 150mA. If you have 25 relays and your impulse is 40ms, then it will only take 1 second to update all 25 relays with only 150mA of current.

[Mikie_lomas]

Can the relays be Set or Reset sequentially? If so, all that's needed is 150mA. If you have 25 relays and your impulse is 40ms, then it will only take 1 second to update all 25 relays with only 150mA of current.

If I am understanding what you mean is current then this is amazing news!

I looked up voltage drop for phone line (i think: 22-24 gauge). With .15 A and 5v there is only a very small voltage drop.

From this, I feel the best way to control it is:

From one main arduino Mega in a central location that sends pulses via cat6 into the roof, into the wall cavities housing the relay circuit?

Does this sound like it would work? That way I could also have a 5v power supply at the main source which I can send out with the cat 6 through the cables.

Thank you for your time.

[Mikie_lomas]

Hi thre guys,

Just a side note question:

Hypothetically, if i did go down the supplying 5v current through cat 6 around my house, could I use the module featured in the below link to:

Receive voltage which would have dropped from 5v-(4.9 - 4.6) depending on the distance sent (between 5-25 metres). Then regulate it up to 5v at 500ma.

What are your thoughts guys?

Step Up Module - Ebay

[dlloyd]

From this, I feel the best way to control it is:
From one main arduino Mega in a central location that sends pulses via cat6 into the roof, into the wall cavities housing the relay circuit?
Does this sound like it would work?

Yes, this could work.

That way I could also have a 5v power supply at the main source which I can send out with the cat 6 through the cables.

Something to consider:
I'm quite sure it's possible to use just one supply for everything. I would consider using a 7.5V (regulated) DC supply that can be used to power the Arduino through Vin and also provide power to all the relays. For relay power, just use one 1N4004 or 1N4007 diode in series with the 7.5V. This essentially creates a separate 6.8V supply for the relays.

This will not be a problem because of the voltage drop across the transistor (0.3V) and the voltage drop through the wiring which would leave something less than 6.5V. Note that the rated voltage of the relay coil is 130% max = 6.5V.

[Mikie_lomas]

I'm quite sure it's possible to use just one supply for everything. I would consider using a 7.5V (regulated) DC supply that can be used to power the Arduino through Vin and also provide power to all the relays. For relay power, just use one 1N4004 or 1N4007 diode in series with the 7.5V. This essentially creates a separate 6.8V supply for the relays.

I have an adapter split and a screw terminal end, so I could power the arduino through the jack as normal, then have it split off into screw terminal, then into ground and then hot to diode and then a common hot line?

Is it perhaps better to have the diode at each of the cat 6 end points or would that make the voltage too unreliable on account of voltage drop in different distances of cabling?

I am starting to get excited about all of this.

Will it limit the longevity of the relays possibly putting them at the end of their tethers for the entire life at 6.5v or is it more like to be less and within the range is within the range?

Would a main arduino and a common 5v power supply , which I step up to a solid 5v -> 500ma at the end of the circuit be better for the life of my project or is there issues with using cheap chinese step up modules.

Should I employ an opto-isolator?

Sorry about all the questions, thank you so much for your responses. i am learning alot

[dlloyd]

I have an adapter split and a screw terminal end, so I could power the arduino through the jack as normal, then have it split off into screw terminal, then into ground and then hot to diode and then a common hot line?

If the adapter is 7 to 7.5V, then yes. At the screw terminal with 7.5V connect the anode of the diode. Then use the other end of the diode (stripe end) for your 6.8V supply.

Is it perhaps better to have the diode at each of the cat 6 end points or would that make the voltage too unreliable on account of voltage drop in different distances of cabling?

No advantage ... only one diode required at the main power supply point.

Will it limit the longevity of the relays possibly putting them at the end of their tethers for the entire life at 6.5v or is it more like to be less and within the range is within the range?

No ... its within specifications. The main thing that would shorten life span is having the pulse duration too long. This overheats the coil.

Would a main arduino and a common 5v power supply , which I step up to a solid 5v -> 500ma at the end of the circuit be better for the life of my project or is there issues with using cheap chinese step up modules.

The main problem here is that you would need a separate module for each relay if the relays are at different locations. Also, more components, more chances of component failure.

Should I employ an opto-isolator?

Good question. There are definitely advantages with this. Note that it would make the circuit somewhat more complex. You'll probably need to design your own relay module for this.

EDIT: This darlington photocoupler could directly drive the relay coil (no extra transistor required).

[Mikie_lomas]

Thank you so much for your time. It is beyond appreciated.

Good question. There are definitely advantages with this. Note that it would make the circuit somewhat more complex. You'll probably need to design your own relay module for this

Yes, I am a bit confused as to how they work..or send a signal. But I do know they can and maybe should be used to isolted relay circuits from microcontrollers?

If it has 4 pins, surely that means two inputs and two outputs. Could a whole bunch of 4 pin opto-isolators be used to send the set and reset message, perhaps I am mistunderstanding how they work.

Basically, yeah I plan to mount this on a perfboard. The only factor stopping me current is that although the 6 - > NC, C and NO fit on a normal spacing, the 3 input pins do not fit on anything unless diagonal, which really does not work.. Not sure what the best method to deal with that conundrum is

No ... its within specifications. The main thing that would shorten life span is having the pulse duration too long. This overheats the coil.

I just looked at voltage drop from 24 gauge with a load of .125, the cable needs to be atleast 14 metres long. Otherwise it will be over 6.5v. Will there be other ways in the transport process that voltage will be lost or should I employ a power supply that is less than 7v?

Thank you for your time.

[dlloyd]

Don't forget that the transistor drops 0.3V. So, directly connected we have 7.5 - 0.7 - 0.3 = 6.5V. This is within specifications. In a different application, I have many 12V latching relays that use an 18V pulse (150%) and have been in service without any failures for about 15 years.

EDIT: Could use 2 diodes in series if you're concerned (5.8V).

[Mikie_lomas]

Don't forget that the transistor drops 0.3V. So, directly connected we have 7.5 - 0.7 - 0.3 = 6.5V. This is within specifications. In a different application, I have many 12V latching relays that use an 18V pulse (150%) and have been in service without any failures for about 15 years.

Awesome news, this will be a much better option than running a whole bunch of arduino nanos!

I have ordered some of these:

Optocoupler

Hopefully they shouldnt be too difficult to figure out once they arrive and they are sufficient.

Thank you for your help my friend.

[DrDiettrich]

I'm not happy with your installation plans. What looks good for a breadboard model, is not normally applicable in a larger area.

Inside a car (5m) 12V are used, for longer distances 24V. These higher voltages will reduce currents, and consequently power consumption and losses. Consider to use such voltages with a central power supply, and break the voltage down in every node of your home automation network. Don't forget fuses, or you risk failure of your entire installation on a local problem.

How do you intend to control the many relays? Individual lines to every relay will sum up into a huge number of wires. Better were a bus system with addressable nodes (I2C, CAN, Ethernet...), that also can be extended at any time. Line drivers are almost required, for secure signal transmission, so that I2C can not be used across a house.

I'd not try to build a cheap and unreliable home automation system, unless I want to make my living from service and repair.

[dlloyd]

Using an opto would provide high reliability and could handle long cable runs. However, you'll need a separate power supply. Yeah, there'll be a practical limit to how many relays you would want to control like this due to the increased wiring and digital outputs required.



EDIT: The relay coil voltage (not counting voltage drop through cable) when pulsed would be about:
7.5V - 0.7V (diode) - 1.5V (Vce) = 5.3V