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- Опубліковано 24 тра 2018
- Mains Opto Coupler
A SAFE way to detect mains from your microcontroller (eg Arduino, Raspberry Pi)
All this plus the sketch here:
github.com/RalphBacon/Main-Op...
As part of my Workshop Automation Project I need to detect mains voltages (why? watch the video!) and this little unit will ensure I don't fry my Raspberry Pi whilst doing so. Can you imagine? Bacon's fried his Pi!
I've included a link here to where I got this device (UK seller) but you can get it many places.
Mains opto-isolator for Arduino and Raspberry Pi (and others) from Moore-estates (UK)
www.ebay.co.uk/itm/3-Channel-...
I've also included a small sketch you can use to test it out but you really don't need the module (or mains) to test out the sketch!
And there was a moment of confusion as to what a PLC was (no, not a public limited company, but a Programmable Logic Controller) so this is the definition:
What is a PLC (Programmable Logic Controller)
www.amci.com/industrial-autom...
I've expressed my concern over mains electricity safety in my video a few times, as I can't afford to lose any viewers or subscribers - so don't take risks with this device. When it's connected to the mains you hands should be nowhere near it. It's all too easy to forget that it is at mains potential and just pick it up!
If you like this video please give it a thumbs up, share it and if you're not already subscribed please consider doing so :)
My channel and blog are here:
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/ ralphbacon
ralphbacon.blog
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I am very very very happy that finally someone got it to make a review on this thing!
Thanks a lot for sharing
Cheers!
Wow! I never expected that level of excitement over such a fairly mundane (but useful) item. Glad you liked it, Parth, and nice to hear from you.
Just checking back through my eBay purchase history and I noticed I bought the L298N Dual H Bridge Motor Controller module that is on my Robot Buggy from moores_estates (the name seemed familiar when you mentioned it.) I think it cost me about £1 more than it would from China but with no long wait for delivery, I really wanted to be getting on with my project and not waiting for post. Sometimes it is better to pay a little more (pardon the pun) for an item for the benefit of waiting a little less. Actually, purchases from China account for a tiny proportion of my eBay activity over the last four years as I do prefer to deal with sellers based here as much as possible. One of my many flaws is I am not a person blessed with a great deal of patience and I especially hate being kept waiting.
Glad to see you back Ralph.
Funnily enough, Nick, just lately I've ordered quite a bit from the UK stores, partly because I want the stuff _now_ and partly because Pi-related items are not necessarily cheaper from the Far East (not kosher items, anyway). It's different for Open Source items for the Arduino (clones).
If my channel ever takes off, financially, I would much prefer to support my local (smaller) outlets anyway. Fingers crossed that over the next year, as I devote more time to this channel, that this happens. Thanks for posting, good to hear from you as always.
Thank you for the video, wasn't entirely sure if this board is good for my project. Pulling it to ground when there is Voltage has the great benefit to say "there is a Voltage" even when the connection between the Board and the Microcontroller is broken. Better say it's on when it isn't than the other way
You could change the logic of the board by using a transistor so that only the presence of mains will extinguish the LED on your own board? I guess a belt and braces solution is safer, you make a good point, Bastian, thanks for posting.
Hi Ralph and thanks for posting this very useful circuit. I have build a pellet burner for my heating system, i used a relay as a switch to detect whether the room thermostat was on or off, i think i might replace the relay with this circuit.
Greetings from Greece
Vasilis K
Good luck with your project, Vasilis Karastergios, take care with the live parts of the board, and thanks for posting.
Love the video....and I approve this message! From: Robert W. Bacon Jr.
Florida, USA.
Right on! We Bacons must stick together! I always thought that "Bacon" would be pretty rare, and that Ralph Bacon would be rarer still (Ralph is not a common first name in the UK). No so! Many, many Ralph Bacon albeit mostly in the States. Oh well...
Thanks for sharing 😀👍
Well done 👍
Sounds is good
Thanks for your post, Asger Vestbjerg, good to hear from you again.
Great Explanation thank you Ralph
Thanks for that, Rabih Brahim, nice to hear from you.
I've building my own home automation project that requires that I detect mains voltage. In my specific application I've got some existing ceiling mounted PIR sensors that provide a switched 240V output. I'm wanting to detect this on my raspberry Pi, and this module caught my attention. Buying this was cheaper than replacing my (rather expensive) Danlers ceiling mounted PIR sensors with ones that have dry contacts.
One surprising thing about it is how there are very few alternative examples on the market. I've found nothing on RS Components or CPC Farnell catalogues like this. You have the optocoupler chips themselves, but nothing I've found that's built up as a module like this. I would have thought there would be a great requirement for sensing a 240V live circuit on a 3/5V input.
Your comments about the exposed live components are well noted, and my personal preference would be to find a module that has all components enclosed in an earthed metal mesh box (similar to ones found in embedded switched mode power supplies). However since this is going to be mounted inside an IP 20 rated box in it's own right, this is of secondary importance.
Don't forget to also check out video #114 where no contact with the actual mains is required at all! Thanks for posting, Anthony, nice to hear from you.
Ralph S Bacon Many thanks for the reference to the contact free method. However I bit the bullet and ordered one of these. My biggest concern was the heat emitted from the 150k ohm resistors on these boards. The last thing I want is a fire caused by underrated resistors. 0.4 watts per resistor each seemed a bit much heat emitted from a small surface area. However I checked data sheets for comparable resistors on RS components and it seems like resistors are power rated according to casing size. These look like either 1 or 2w rated resistors (CFR 100/200 carbon film), which have a max operating temperature of 155 degrees Celsius.
That makes me happier using this unit. However I wish I saw the contact free voltage sensor first. That does look like a safer option.
For me, it is best to have the habit of ALWAYS checking that a mains level device/circuit is UNPLUGGED before handling. (When I unplug I put the plug beside the DUT) Only use one hand.
Using only one hand with mains electricity is a rule to live by (literally) for most electricians. I've made mistakes, like unplugging the wrong plug and then getting a shock. Silly mistakes that could cost me dearly. I like your way of working here, Kenn, safety first.
Hi Ralph. Thanks for the informative video. Interesting little idea. On the subject of the wire, as someone already mentioned below, it's more than likely to be CCA wire (Copper Clad Aluminium) hence the refusal to solder properly. A simple test is to strip a small length of the insulation back & hold the strands over a naked flame. If it's CCA it will burn like cinders. If it's pure copper it won't (just discolour slightly). When buying, a quick check is to see what the weight is compared to another seller of the same item/length. Obviously pure copper will be heavier than CCA. As usual it all comes down to cost. CCA is cheaper to produce than copper so bigger profits! CCA is very prolific in cat5/cat6 cables as a cheaper alternative.
Undoubtedly the case, NIck, but I've packed it all up for fellow Arduinite Gary to take possession of, so I can't actually do the flame test. Of course, he might want to if he reads this!
Funnily enough, when I bought my long, external, UV-protected ethernet cable for the workshop I had to be very careful that it was 100% copper and not like you say, copper clad aluminium. I guess that's why the cable I ended up with (UK supplier) was three times the price of "cheapie" ones on Amazon (from the Far East) and the like. But I'm getting as good as (perhaps better than) my old "office", around 65Mb/s down and 18-19Mb upload so I consider it money well invested, given that I have huge HD UA-cam videos to upload. Possibly overkill for "general" use, though!
I never considered that this might also be used for general wiring cable, though. If it looks too good to be true... Caveat Emptor!
Caveat Emptor indeed. On a different note i'm intrigued how you are planning to connect the "live"( or should i say "hot" for our transatlantic fellows) to each respective mains load (e.g. Heater, Light and/or other) mainly as you will be dealing with sources fused at markedly different ratings (e.g.Heater 13A, Light 6A etc.). Are you going to fit & install a separate fuse holder with a low (500mA say) protection fuse at the supply source for added protection?. Also maybe a triple pole isolating switch (as is used to isolate a bathroom extractor fan) as this would provide complete isolation from the live wires coming into the opto board. just some food for thought!
My design plans haven't extended that far yet, Nick.
In general terms, I was thinking of taking a feed from the respective appliances back to this board, given that they are all in fairly close proximity, mostly near the consumer unit. I'm not sure that a further level of isolation is required (given that we have optocouplers on board).
In-line fuses might be an option, although I would have thought the lowest level fuse I could get would be appropriate (I can find 100mA fuses for 250V AC, but no lower ones). I need to think about how I am going to do this a bit more first.
Nice little board.
Yes, it is, Javier, and might save my Arduino or Pi or whatever I have plugged into it as my Workshop Automation project goes forward. Thanks for posting.
Nice little device as well as the video.
Thanks for that, Pekka Grönfors, nice to hear from you.
All Big Clive fans recognise "this safety thingie" as a Cliff Quick Test. ;)
You got that right!
Hi Ralph
Thankyou for a very well explained topic. I have one question, can these opto coupler devices detect current? To detect if a device is ON, should the opto detect mains current or mains voltage.
Thankyou
John
Not really. The intent here with these particular modules is that the microcontroller can switch on a high voltage (eg mains 240v) without actually getting involved with the high voltage itself.
The μC turns on the optoisolator LED which, in turn, turns on a Triac which allows the mains current to flow into whatever is plugged into it.
It's not designed to _read_ whether there is mains voltage present (which is what you want). You CAN do that with an optocoupler by wiring the optocoupler with a high value (eg 300KΩ) resistor to the main bit of the circuit and then detecting that.
Hang on... here's a link: bit.ly/402Itdg
@@RalphBacon Thankyou for your reply, your videos are very well made and a nice voice to listen
Can I give input voltage 440v ? (i.e two phase from 3 phase)
No, absolutely not!!! This is designed for 240 volts only! Please don't do anything dangerous, Kevin, I wouldn't want to lose you as a viewer!
Hi Ralph, is secondary supply comming from raspberry pi GPIO pins at 3,3V ?
Would that be OK if wired like that or a another secondary source at 3-5V would be required in addition to Pi or microcontroller ? Thanks for awesome videos !
This board can run from 3v3 or 5v as the secondary supply, according to the seller's website. Both Pi and Arduino have 5v available so that's what I would probably use but you might want to use 3v3 (ensure the Arduino's 3v3 can supply the necessary current, as the 3v3 is limited on the Arduino).
Wow, thanks for the quick answer... even on Sunday ! :-)
Correct me if I am wrong but Pi GPIO input voltage should not be higher than 3v3 to avoid a damage. I believe secondary circuit with Pi should be at 3V3 and with Arduino 5V to make it simple. Now focusing on required current for secondary circuit, I believe it will be very very low. With Arduino it would be a 5V circuit with 10k resistor and optocupler light sensing switch (??) in series. Do you think current will be higher than 5mA in any case ?
You are correct about the 3v3 and 5v for the Pi and Arduino, respectively. I, too, suspect the current will be very low.
The output (for each channel) is connected to the collector of an SS8050 NPN transistor, which is connected, in turn, to an LED and a 10K resistor. So you can connect the VCC to 5v directly (or 3v3), GND to ground and each output will be pulled to VCC when the mains has been detected. Make sense?
It makes sense, thank you for your help Ralph.
Just a tip for the records. I focused on a single channel board from same e-bay supplier. Secondary circuit is different compared to video 3 channel board, just optocoupler and 47k resistor (no led, etc).
Hello Ralph, I'm back. Naughty step time as you're messing with the mains again!
This is an over-complicated, crude and dangerous way to sense the presence of AC mains straight from the Chinese street market. It adds a permanent tail circuit into the mains then uses a huge energy sapping resistor and rectifier to produce a low DC voltage into the opto-isolator. You've got mains on the same circuit board as the low voltage stuff, no enclosure, no spark gaps ..... deadly. Then to cap it all it's output is binary. How are you going to enclose it? Where are you going to mount it?
You may as well use a mains LED, light bulb or a neon and sense that with a phototransistor with high=OFF logic.
If you want to measure several AC outlets in your workshop, use current coils/transformers (CTs) instead. Non contact, inductance, so intrinsically safe. With a DC offset bias signal you can measure the actual AC peak-to-peak current if you wish. Set appropriate thresholds on the analog port of the microcontroller, in your case just above zero. You can set the logic high in the code or use pull-ups. This solar energy hobbyists use this method extensively. If your workshop has a small breakout box the CTs can go in there where the live wires are easily accessible.
Here is how to do it: openenergymonitor.org/forum-archive/node/156.html
Some of the latest Hall Effect sensors can also detect mains presence with a bit of fiddling, as used in those non-contact mains probes. I believe the driver boards are becoming standardised now. You could then simply strap the HE sensor to the mains cable.
Anything but this board, anything ......
Oh dear, I wondered when/whether you would be berating me about this 😳
To be honest, whilst I generally dislike anything with mains potential near my µControllers, I thought that this unit, complete with its optocouplers was quite a neat way of detecting mains. If this is mounted nicely in, for example, a ceiling recess in an enclosed box (I'm thinking of my workshop lights or heater here) all it needs is a couple of power lines and then a single detector line to the Arduino, ESP8266 or Raspberry Pi.
But, to preempt further admonishment, I do hear what you say about using alternative methods such as coils which are even safer; perhaps I will investigate those too, before taking the plunge one way or the other.
In the meantime, I'll make my videos from the naughty step (again). Sigh. 😜
The outside Naughty Step, in the rain, overnight with no tea.
You are right in tackling this as a subject though. All Arduinites are going to have to sense or measure mains AC at some time. There are no easy solutions which is why your eyes lit up and you went for this board. Trouble is, your eyes may well light up.
The CT solution above is easy though. I use it in several places in my house including measuring 240V 16A AC from my solar panels. The Open Energy Forum chaps did a good job explaining it all and now there are several UA-cam copies out there. The only Gotcha is the choice of turns and calculating the burden resistor. However the maths is simple. If you can't understand it then you should not be playing with mains anyway? Make sure the burden resistor is mounted directly onto the CT though. If it goes open circuit very high voltages are induced to ruin your day.
These are the CTs I use ...
www.nuvotem.com/en/products/new_nuvotem_current_transformers_in_schukat.shtml
They are really small and will fit inside a consumer unit, breakout box or even a surface mounted patress box
I can email you my design notes if you wish to save you the bother.
===============
Ref Hall Effect, here is a chap doing a good job but more detail than you need. I will emulate this and see if the HE sensor can save some circuitry. I use a similar logic level latching HE sensor on my bike and it interfaces directly to the Arduino.
ua-cam.com/video/p1pQGql65LE/v-deo.html
Again, I will send you my notes if you wish ... but I hope you get there first!
I am in Solihull, just up the road from you
This has definitely peaked my interest.
I have a clamp meter so perhaps should have considered alternative solutions too. I am still investigating various hobbyist approaches to mains detection so bear with me. My requirements are probably simpler than what the approach outlined by you offers; I just need an indication of mains presence (digital) rather than any kind of measurement of current flow. YMMV.
Thanks for the links, they were useful. On the above basis, I'm coming off the naughty step now, possibly a temporary reprieve...
I understand you just need a binary sense of AC presence
The CT will induce a sinusoidal voltage in the secondary that you read across the burden resistor. Feed this into the Arduino analog (or digital) and look for OV over say 1 second so you dont need to rectify. That will then = OFF.
I have some spare CTs if you need any
Next week I will investigate putting a Hall Effect sensor in a ferrite ring to sense presence ... if it works it will be the simplest solution
www.aliexpress.com/item/1PCS-5A-Overcurrent-Protection-Sensor-Module-AC-Current-Detection-12V-Relay-Module/32858449954.html?spm=2114.search0204.3.1.606b5adfq87v6E&s=p&ws_ab_test=searchweb0_0,searchweb201602_5_5722916_10152_10151_10065_10344_10068_10130_5722816_10324_10342_10547_10325_10343_10340_10548_10341_10696_5722616_10192_10190_10084_10083_10618_10307_10301_10303_5722716_10059_100031_10103_10624_5722516_10623_10622_10621_10620,searchweb201603_1,ppcSwitch_5_ppcChannel&priceBeautifyAB=0
The module will work perfectly for sensing if mains is switched on/off. But please do not use the module in situations were the load is switched on a long time with a modest/lower power usage.
This module uses roughly 0,4 watt per channel at mains side when switched on. Secondary power usage will be added to it.
This extra used power is quite significant when used e.g. with a 3-5 Watt led lamp.
Hmm, interesting, and I concur with your maths. Not something I would have considered, frankly, but you are correct that it is significant when compared with an LED lamp. And that's just ONE channel - for all 3 channels it is just over the 1W mark. Well, now we know so thanks for bringing that to our attention, a good heads-up.
Hi Ralph-- the controller im working with is looking for a high output-- any ideas
Just making a GPIO pin go HIGH would do the trick, or did I miss the question?
@@RalphBacon thanks -i figured it out watching your video a couple times-- i was trying to monitor a high voltage string of safety switches in series) - with each switch goinging into an opto coupler input- then into my controller board-(24vdc inputs)
Where did you get the mains safety switch? What do manufacturer’s call or label this device so I can look for it in the U.S.? Thanks. P.S. I do not mind how long your videos are. It’s pure you and I like it!!!
The US name for "mains" electricity, Bruce, is as you well know not "mains" (see english.stackexchange.com/questions/20596/is-there-a-term-for-mains-power-in-u-s-english ) so I checked all the alternatives for you.
No joy.
In the UK it is called a "quicktest mains connector" and the price ranges from £21 (unbranded, not sure I'd want one) to a branded £35+. Unfortunately, I can see no way of getting one to the States without exorbitant shipping costs. However, I'll leave you to Google further! I use mine now and again and it is very, very safe (as can be, when using household electricity).
I'm pleased you like my (long) videos! I'm trying to make them more often and shorter but that's an aspirational goal not a promise! Thanks for the post.
Ralph S Bacon Thanks for the quick response. I see what I can find here “on the other side of the puddle”.
Hi Ralph, yes very strange, the same board (100% the same) is also available on AliExpress for half the price (5 Euro's), so these boards are not made in the UK, only resold as such?
The single optoisolator version is only 1,27 Euro.
Indeed, Javier, this is the problem that all local suppliers (resellers) must face. The same product for a quarter of the price. Just factor in up to 60 days of delivery time. I could never have started this channel if I could not have bought my items from the Far East. But now I try and balance that out a bit; support the local economy and all that, and let's face it, the UK definitely needs all the support it can get - now and post-Brexit!
The way local suppliers can survive is by adding value. Shorter delivery times, free postage, discounts for multiple purchases, a good customer service, a decent newsletter for other products. And possibly innovative products that you just can't get from the Far East (not cheaper, anyway). Raspberry Pi anyone?
Yes, you are absolutely right about the local (and European economy) but for true market dynamics you have to give people options to buy wherever they feel comfortable with.
Raspberry Pi is a good example, I have several iterations that I use for a couple of projects, I always bought the boards from my local supplier in Eindhoven.
Hi Ralph, it would be a good idea to use the correct colour AC wires for the supply. It acts as another warning of what's attached to the end :)
Absolutely, John. I'm thinking that this would be installed almost as part of the internal wiring, and thus running single or double red wires or twin red and earth even for one of them. And a huge sticker on whatever this is placed in to warn users that mains is inside!
Interesting little thing. For the price I'd be tempted to make it myself (just as safe) :-).
Leave the capacitor out and you have a zerocross detector.
The wire you can't solder is probably made from scrap from Fukushima.
Yes, there's no doubt that we _could_ make this ourselves, Ed, but even though this is a Far East-sourced item it's built to a relatively good standard and I just don't want to be soldering bits like this together if I can avoid it! I want to _use_ the modules to "get on" without all the faffing! That wire is now going to a good home, and the thought is that it might be copper coated aluminium or something equally bizarre. Thanks for posting, nice to hear from you.
Ralph S Bacon oh I fully agree, I prefer using modules when available......... Unless they cost 12 pounds and I put them together for less than 2 euro :-), thus saving money for other modules.
I hope you are doing well. Hard to lose a parent
I hear you, Ed. And I'm with you, most of the time. It's a balance, but sometimes cost overrides all other considerations. It can make the difference between a viable, fun product and one that is ridiculously expensive.
And thanks for your concern, Ed. Yes, it _is_ hard to lose a parent, as others have indicated on my blog. But my dad continues to inspire me to continue, as he would have loved all this. Thanks for posting.
Hello American makers, this particular model is not available in the US
Thanks for the info, Carole.
Somewhat concerned when you started pulling that “active” connection and inserting it in to the terminal block. Nylon tweezers may have been the stool to use here
I was being _very, very_ careful, believe me, Bruce! But you are correct, I should have displayed better safety practices and I will take this on board for future videos. Thanks for posting and your concern 😀
Can i use it as a zero point detector?
I'm not quite sure in what context you're asking this question, LazMouse. The Arduino will be able to determine zero point crossing but so will a zero point optocoupler. What is it you're trying to do?
Ralph S Bacon i’m trying to do a threephase high power ac controller, was looking to make it simpler than i could, minimal soldering. Were i live electronic parts is too expensive to buy in retail. Found this module and was wondering if i remove that capacitor i should be able to get a pulse at the outputs.
can i have the wire plz
Yes, you can, Gary. Go to my channel home page (ua-cam.com/channels/8Ob-HnnmhlgSv5Vs_i32TQ.htmlabout) and find my email address and send me your postal address. I'll send it out after the Bank Holiday. I hope you find a better use for it than me! Enjoy!
Steel wires?
Um... probably?
@@RalphBacon steel won't solder without brazing. but, dont take my word for it. I tried to solder copper wires to steel before, never worked.
Check that wire with a magnet. Might be steel or iron.
Just checked it as per your suggestion, Mr Johnaz, no luck. I suspect it is copper clad aluminium. If it turns out NOT to be that then I have no idea what it might be. Thanks for that suggestion, nice to hear from you.
I think you will find the NONE soldering wire is aluminium so will never solder and is not much good for heavy loads that will be China then??
Not sure if it originated from China, Bob, it was a UK-based eBay seller. Frankly, I'd be surprised if s/he even realised what it was that they were selling, it's all just "stuff" isn't it? But it's going to a new home and I hope it's OK for the new owner! Thanks for your post, always good to hear from you.
you can solder aluminum, just use proper flux/solder paste
en.wikipedia.org/wiki/Flux_(metallurgy)
" Rosin, tallow, olive oil, and zinc chloride - for aluminium "
ua-cam.com/video/_mYkM9lHMho/v-deo.html ua-cam.com/video/FmjdXKyDEWY/v-deo.html
Hmm, interesting but not so useful when you think you have COPPER wire and it turns out to be something else! But thanks for the links, very useful. 👍
Hi Ralph ,thanks for this video I used this mains detection board to detect if the door was locked on my Arduino washing machine project
You explained it really well.I also used your tutorial on the rotary encoder to set the programme of the machine
Here is the video of my completed project ua-cam.com/video/vxtv7HNJ168/v-deo.html
Thanks again
Rgds John
I'm *well impressed* John. Not only did you have the knowledge and courage to rip out all the existing control boards and wiring loom, but you also managed to replace it all with the functionality of one of your liking. Perhaps you should release all your code into the public domain for others to use? Just put the correct type of licence on it to prevent washing machine manufacturers using it for commercial purposes unless they licence it from you!
Regarding the actual video I have the following suggestions:
1. Do a voice over. Silent videos are not as well received as ones with sound. Don't go mad, just a bit of explanation of the direction your project went would be enough, timed with the still photos.
2. Speed up (or edit out) the actual real-time video of the complete washing cycle. If you don't have the software to do this just cut out the (dare I say) boring bits and put up on screen "15 minutes later..." or something similar.
But that's just a suggestion. I watched it and skipped the "boring bits" as I was intrigued as to what the display was going to show next.
As I say, very impressive, and congratulations on getting it all working.
Man, never solder mains? Hope you don't look inside any consumer electric, they are all soldered....
Indeed they are (from non-UK/EU sources) but that doesn't make it right!