Safe In-Wall AC to DC Transformers??

[GertSanders]

found these:

http://www.aliexpress.com/item/Free-Shipping-25pcs-0-25A-250mA-250V-3-6x10mm-Fuse-Slow-Blow-Glass-Axial-Leaded/32452469177.html?spm=2114.01020208.3.138.0Cb2oJ&ws_ab_test=201556_3,201527_3_71_72_73_74_75,0_0

[Cliff Karlsson]

If I want to use a relay for in-wall use. Could I use the same Slow Blow fuse, thermal fuse and varistor to get it to be more safe?

[novicit]

This has been an excellent thread! I am left with one practical question though. How does one safely mount the thermal fuse on the HLK-PM01? Even if the thermal fuse thru hole on the PCB was exactly next to the middle of the HLK-PM01, the lead will still need to run 2+cm to the top of the HLP-PM01, then another 2+cm back down to the PCB. Only the thermal glue holds it in place. It seems it could easily come loose with minimal pressure - and remember it is 110 or 220V! Of course the leads would be protected by electrical tape or shrink tube, but it is still not firmly secured. Plus it is more likely that the leads on both sides would be closer to 3cm, plus the 1 cm for the fuse for a total of ~7cm of high voltage 'leads' not securely tied down to the PCB. I am only a hobbyist, so I am curious to hear others thoughts on this. Also, note that this board (http://forum.mysensors.org/topic/1540/110v-230v-ac-to-mysensors-pcb-board) has great protection, even fuse & varistor on the low voltage side. How would one mount a thermal fuse on the HLK-PM01 without having a 'loose' lead running to the top of the HLK? Or am I over concerned.

[GertSanders]

I would suggest that the PCB have a cutout UNDER the HLK-PM01, so that you could stick the termal fuse under the powermodule against the bottom.
If you look at the images of an opened powermodule, then you will see that the internal PCB is on top. I would expect the heat from any problem to be noticable on the bottom as well.
Could be a safer option (less long wires) ?

[TD22057]

This has been a great thread with a lot of good information. I'm still a little worried about putting something like this in my wall though. What are peoples thoughts on benefits of this approach versus using something like a Samsung cube charger which is about a 28 mm cube (without the prongs), handles 120/240 V, and is probably very safe?

[GertSanders]

My guess is that the HLK-PM01 is of the same quality, but it only gives 700mA @ 5V. On my repeater it never feels warm at all (and this is in a completely closed box).
You could add a temp sensor to monitor and set an alarm in your home control system, maybe a solution to feel more secure.

[lrtsenar]

What do you think about this ? 1.79$ 5V @ 700mA dim: 3cm x 2cm x 1.8cm :
http://www.ebay.fr/itm/321846469504?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[GertSanders]

That is similar to the HLK-PM01, but without any of the certifications the HLK-PM01 received. And it is completely open, so unsafe in my view.

[pdey]

I use these in Australia:
https://www.clipsal.com/Trade/Products/Electrical-Accessories/Electronic-Accessories/USB-Charger

AS/NZ safety certified, etc.

[Chester]

@pdey What is the per unit cost of those? And do they fit easily inside the wall box say sideways to allow for arduino etc to also fit?

[Cliff Karlsson]

@Chester said:

@pdey What is the per unit cost of those? And do they fit easily inside the wall box say sideways to allow for arduino etc to also fit?

I looked around a little and they where pretty hard to find but the prices I found where 30-35 $/unit + shipping. To expensive for me.

[pdey]

@Chester: They're usually about $30-35 per unit. On the expensive side, but I'd prefer to have something buried in my wall that I know I won't have to pull out in 12 months time - and also that is unlikely to start a fire...

They're quite small. Designed to fit into the Clipsal faceplates for Cat5/Cat6 jacks.

[sundberg84]

http://www.ebay.com/itm/Ceramic-Slow-Blow-Fuse-3-6-x-10mm-Axial-Leads-125V-250V-0-1A-6-3A-10-30pcs-/111433875797?var=&hash=item19f1fa0155

Hi all! I tested the Slow BLow fuse after @m26872 was a bit suspissions and it didnt blow. Looks like its some sort of bi-directional TVS and not a fuse. I could "run" a 1000Watt vaccum on this "fuse" which at 240v/200mA should blow at 48 Watt.

Good find by m26872

[petewill]

@sundberg84 Thanks for posting this. I'll have to take a look at mine to see if I got the same thing. That sucks that you didn't get what you ordered. Can you post a link when you find some new ones that you plan on using?

[nunver]

@petewill Thank you very much for this excellent thread. It's great to see the community is in agreement on how to implement a safe power supply.

Just one comment; for 220V, shouldn't we opt for a lower amp rating fuse? If we stay with 300 mA, I am thinking we will not protect the device?

[dakky]

hmm have some questions too:

1. is this setup only needed/recommended for in wall setups? or do you use this for all ac/dc converters?
2. does someone has a picture for me to share, how this looks in reallive?
   I'm not shure how to build my node in this case
3. what kind of cables (profile) do you use for the "high voltage" parts?

[sundberg84]

@nunver - A question i have also asked myself doing my PCB - i dont know if it makes any difference but HLK has a maximum imput of 200mA (1A spikes) according to its datasheet. What is the logic here and why - anyone that can explain?

@dakky I think this would be just as great for a outside ad/dc converter, the main idea is to protect us but in-wall you dont have the ability to remove the heat made from the HLK that easy. Pictures from my PCB here (Not completed) but based on this thread.

[petewill]

@nunver I am by no means an expert in this (which is why I started the post :)) but it is my understanding that the fuses are there to protect your house (not sensor) from damage if something goes wrong. I can't remember where I read it but it was advised if the 300ma fuse blows the HLK should be replaced as a safety precaution.

@dakky

is this setup only needed/recommended for in wall setups? or do you use this for all ac/dc converters?

So far I have always used phone chargers for all my sensors which haven't been in the wall. I have never had an issue. I use the phone chargers because I can usually get them free from work when they are recycled. The HLK is much smaller though so it's a great option.

I'm not shure how to build my node in this case what kind of cables (profile) do you use for the "high voltage" parts?

Good question. I'd be curious to hear what others are doing. I haven't had time to build an in-wall sensor yet but I was planning to use 14 gauge wire because that's what is in most of my house.

[nunver]

@petewill I am no expert either, which is why I am reading this thread :smiley:. It is true that we protect the home, not the device. But fire starts at the device if not properly protected. The rating of the device says absolute maximum 0.2 A. This translates to 24W for 120 V and 44 W for 220 V, if my math is correct. Since this is way above the supply rating of the device, we must consider 0.2A as really absolute maximum. So, if we want to protect, in my opinion, we need 0.2A fast acting fuse.

Again, not an expert, so please disregard this post if I make no sense :smiley:

[sundberg84]

What about that the HLK can manage spikes up to 1A (according to datasheet). If so, this will blow the fuse even it its not necessary, atleast if you have a fast one?