powering relays via separate power - same master PSU to 2 separate PSUs is OK?

i have a project with Arduino Mega to control relays that activate 24VAC air-conditioning dampers.

i am currently powering the relays from the same power i am using for the Arduino, 240VAC to 12VDC adapter + 12VDC-5VDC converter (LM2596S ) (I use 12VDC in one part of the project). I hooked it up without the 24VAC parts in circuit, and all was well, but once i got the relays connected to the 24VAC parts, i am getting lots of disconnects (using W5100 Ethernet) and an unhappy situation all round!

i have these opto-isolated relay boards, but not currently using JDVcc - but think using this will assist reducing the issues?

so, question: can i have a 'master' ~8VDC power in from the LM2596S and 2 x AMS1117-5.0 eBay modules to create "separate" relay coil power and Arduino power?

or do i have to use a COMPLETELY separate 5V PSU for the coil and a separate 5V PSU for the Arduino?

Hi, It would be best to have a separate 5V "wall wart" or whatever to run the relay board itself.

Review how to actually isolate things HERE: and see the section on "Optical Isolation"..

Also review "Grounding".. You should have a "common ground point" which is then connected to the building ground. This typically would be the negative terminal on your main power supply and the Arduino ground and all the other device grounds would run separately to that common point. Also check: is it better with USB Disconnected from your programming computer? That's another path for Electromotive Interference.

Let us know what helps...

I wouldn't use that one - the pins are bent!

The fact is, you don't actually have to use a separate supply for the relay module, but you do have to pay special attention to how you connect the supply lines and provide decoupling with a couple of hefty capacitors, notably one where the supply connects to the Arduino.

It is not only the grounds that must be connected in a certain way, the supply lines must match and all wiring must run in pairs in ribbon or "figure 8" wire. This is second nature to experienced engineers, but a trifle difficult to explain in detail.

or "figure 8" wire.

Do you mean twisted pair ?

terryking228:
Hi, It would be best to have a separate 5V "wall wart" or whatever to run the relay board itself.

OK, done, improvement noted. it actually runs now, but still has drop-outs.

for the Arduino Mega PSU - should i use a >5V supply?

the one i am using is a 2A one, but could i use a 9V 2A one? it has to supply the Mega, 1 x W5100 Ethernet board and 5 x DHT22 sensors.

i have not added any electrolytic capacitors, but i have a 1000uF 25V one i can add at the Arduino? i also have some 0.1uF ceramic capacitors - could i add these in various places - like on the W5100 board power lines?

Review how to actually isolate things HERE: and see the section on "Optical Isolation"..

yes, that site was VERY useful.

my 6 relays are all opto-isolated now.

Also review "Grounding".. You should have a "common ground point" which is then connected to the building ground. This typically would be the negative terminal on your main power supply and the Arduino ground and all the other device grounds would run separately to that common point.

yes, i have 'star' grounding, but i don't have the Arduino back to the star (yet),

should i add that to the star and also add the W5100 back to the star (not the Arduino)

and should i ground the 5 x DHT22 sensors at the star too (not the Arduino)?

i am yet to add my mains wiring, but should i add the earth pin to the star too?

would an EMI filter be necessary (the 240VAC is for the inline 90W fan)

Also check: is it better with USB Disconnected from your programming computer? That's another path for Electromotive Interference.

yeah, USB not issue, only started with the 24VAC motor dampers (these i have noticed have relays inside that click when the damper reaches full open and full close)

Let us know what helps...

helping immensely!

cheers!

also should the ICSP wires between the Mega and the W5100 Ethernet board be 'twisted' too? i didn't think so - but wondering?

Paul__B:
all wiring must run in pairs in ribbon or "figure 8" wire.

can you explain the advantage of this non-twisted cable pairs versus actually twisted pairs for DC wiring?

Wareemba:
can you explain the advantage of this non-twisted cable pairs versus actually twisted pairs for DC wiring?

Yes, it's easier to connect if it is not twisted.

(Twisted pairs are used for signal wiring, such as audio or Ethernet. Pretty much irrelevant for supply wiring.)

@Paul,
That's meter lead wire (AKA high strand count/small strand/flexible insulation)

It is very similar to battery lead wire used in the RC hobby industry (same criteria only much higher current rating due to more small strands)

Let us know what helps...

helping immensely!

I think I am speaking for Terryking228 when I say:

You seem to have misunderstood the question. The question was not a request for recognition of help.
The question was a request for information regarding WHICH of the suggestions submitted by members in their replies was of help resolving the issue. The way we work here is by answering questions and making suggestions. We have no way of knowing WHICH suggestion has been beneficial without feedback from the OP, hence the request:

Let us know what helps...

It was not intended to mean :

"Are we being helpful ?"

We would NEVER ask such question because we know we are trying to be helpful and we don't need to ask you for acknowledgement of our intent to help. We need you to give us specific feedback so we can zero in on the solution.

helping immensely!

is not very helpful in that respect (no pun intended)

What we would ask is:

"Which of the suggestions submitted has addressed your issue ?"

or

"Have you tried any of the submitted suggestions ?"

or

"Have any of the suggestions "Worked" ?

Whether meter lead or power wire, that is the form of cable commonly called "figure 8".

raschemmel:
What we would ask is:

"Which of the suggestions submitted has addressed your issue ?"

or

"Have you tried any of the submitted suggestions ?"

or

"Have any of the suggestions "Worked" ?

so you ignored/missed/did not read the first & sixth lines of my reply to Terry, skipped a whole bunch of new questions arising from the information provided by Terry and based on the last line of my response, went deeply into a whole post dedicated to semantics? not schematics?

is this the norm around here?

Paul__B:
Yes, it's easier to connect if it is not twisted.

(Twisted pairs are used for signal wiring, such as audio or Ethernet. Pretty much irrelevant for supply wiring.)

OK, thanks!

I do note that I have found my twisted wires neater as they seem to be easier to manipulate inside the confines of a box.

so you ignored/missed/did not read the first & sixth lines of my reply to Terry, skipped a whole bunch of new questions arising from the information provided by Terry and based on the last line of my response, went deeply into a whole post dedicated to semantics? not schematics?

is this the norm around here?

Actually, no. Once in while people skim or don't read all the replies.
I guess I'm the one who misunderstood the post . My bad. Glad Terry was able to help.

I do note that I have found my twisted wires neater as they seem to be easier to manipulate inside the confines of a box.

For what it's worth. Professional techs use a drill to twist the "twisted pair". Tie one end somewhere , step back and pull the trigger.

raschemmel:
What we would ask is:

"Which of the suggestions submitted has addressed your issue ?"

or

"Have you tried any of the submitted suggestions ?"

or

"Have any of the suggestions "Worked" ?

here we go, updated my previous post to comply. see bold text:

terryking228:
Hi, It would be best to have a separate 5V "wall wart" or whatever to run the relay board itself.

this helped.
I added separate power supply..

OK, done, improvement noted. it actually runs now, but still has drop-outs.

for the Arduino Mega PSU - should i use a >5V supply?

the one i now am using is a 2A one, but could i use a 9V 2A one? it has to supply the Mega, 1 x W5100 Ethernet board and 5 x DHT22 sensors.

i have not added any electrolytic capacitors, but i have a 1000uF 25V one i can add at the Arduino? i also have some 0.1uF ceramic capacitors - could i add these in various places - like on the W5100 board power lines?

Review how to actually isolate things HERE: and see the section on "Optical Isolation"..

yes, that site was VERY useful.

the suggestion to read that webpage helped.
based on that information I disconnected the 5V lines between my Arduino and the relay boards, removed the Vcc-JDVcc jumper and ran 5V lines from my Arduino to the Vcc connection next to the In1 & In2 of the relay boards, but no ground from the Arduino to the relay boards.

my 6 relays are all opto-isolated now.

Also review "Grounding".. You should have a "common ground point" which is then connected to the building ground. This typically would be the negative terminal on your main power supply and the Arduino ground and all the other device grounds would run separately to that common point.

I don't know if this helped.
as I already had a star grounding layout to my main 5V PSU. I DID have the Arduino connected to this GND, but disconnected it as in Terry's page it said:

The ONLY connection to Arduino would be
•Relay board VCC to Arduino +5V
•(signal pins to In0, IN1 etc)

yes, i have 'star' grounding, for my relay boards but i don't have the Arduino back to the star (yet - but I am considering trying this as well),

should i add that to the star and also add the W5100 back to the star (not the Arduino)

and should i ground the 5 x DHT22 sensors at the star too (not the Arduino)?

i am yet to add my mains wiring, but should i add the earth pin to the star too?

would an EMI filter be necessary (the 240VAC is for the inline 90W fan)

Also check: is it better with USB Disconnected from your programming computer? That's another path for Electromotive Interference.

this did not help.

yeah, USB not issue, only started with the 24VAC motor dampers (these i have noticed have relays inside that click when the damper reaches full open and full close)

Let us know what helps...

all of you typed out words are helping immensely!

cheers!

also should the ICSP wires between the Mega and the W5100 Ethernet board be 'twisted' too? i didn't think so - but wondering?

raschemmel:
Actually, no. Once in while people skim or don't read all the replies.
I guess I'm the one who misunderstood the post . My bad. Glad Terry was able to help.

OK, cool, sorry if I am not quite fitting in around here... I will try to be more specific in future...

For what it's worth. Professional techs use a drill to twist the "twisted pair". Tie one end somewhere , step back and pull the trigger.

YAY!! so does that make me a 'professional tech'

I use my bench vice at one end and my Makita at the other...

but I also just use Ethernet cable that I cut open and use the already twisted pairs for my 5V lines and signal lines...

terryking228:
Review how to actually isolate things HERE: and see the section on "Optical Isolation"..

hi, on that page, the some text says:

Powering Arduino Itself: (Different Subject!)

but it goes to a page that just talks about the chip? not powering the boards? or am I missing something?

I had made this diagram a while ago but never needed to post it. It shows how to make connections for opto-isolation.

dlloyd:
I had made this diagram a while ago but never needed to post it. It shows how to make connections for opto-isolation.

thank you, yes, i have my relay boards wired like that.

but i am confused as to whether to add a link between the Arduino and the 'star' earth.

the http://arduino-info.wikispaces.com/RelayIsolation guidelines state:

•Pay special attention to Grounding: Create a single common ground point in the power section. Connect the Computer/Electronics ground to it at only that one point.

but the https://arduino-info.wikispaces.com/ArduinoPower states:

The ONLY connection to Arduino would be
•Relay board VCC to Arduino +5V
•(signal pins to In0, IN1 etc)

so do I ground the Arduino at the "star ground" where all the relay's go back to as suggested by guideline 1 or do I not ground it at the star as suggested by guideline 2?

and i also found your posts from December last year, and also could not find clarity on the GND from the Arduino...

so because I have two 'power sections' I don't need to connect them?

i have all my Arduino side elements (5 x DHT22,s 1 x W5100 module, 1 x OMRON SSR) connected at the one GND pin on the Mega board.

and all the relays are connected to the one point on the 5V relay PSU.

and just because i need to be 100% sure, it is OK to connect the Arduino 5V to this SSR, it is isolated isn't it?

1000×1000 124 KB

it doesn't work if it is connected to the relay PSU.

and i also found your posts from December last year, and also could not find clarity on the GND from the Arduino...
so because I have two 'power sections' I don't need to connect them?

Correct. From that link, the diagram shows an "X" on the GND terminal which means no connection. It also shows star grounding for items connected to the Arduino. Make no ground connection from the Arduino GND or star GND to the Relay board's power supply ground or opto-isolation will be lost.

and just because i need to be 100% sure, it is OK to connect the Arduino 5V to this SSR, it is isolated isn't it?

Yes, it has internal opto-isolation. The SSR's 5V input (on the other side of that image, labelled 3+ on the image) would go directly to an Arduino output. The GND terminal (on the other side of that image, labelled 4- on the image) needs to be connected to Arduino GND.

OK thanks, I will tidy it up tonight and add a 1000uF capacitor to the Arduino supply lines, and see how it goes...

I should run it with the 240V mains connected before I get too advanced in EMI work, so will get that in too...