Last week I carried out an elektrical safety test on the HLK-PM01 to NEN 60101 (Dutch test for medical equipment) and it performed pretty well. I will try to post the file, after I removed some private information 
Furthermore I am building a automated load tester that relates variable loads to output voltages and surface temperatures, based on an Arduino Nano.
Short update ... yesterday I asked or Chinese friends from Alie to send a HLK module to our test friend.
I also did an insulation test with 1000 Volt. The test shows more than 1000 MOhm between ac and dc. So far so good.
Sorry for the language thing. I will try to get some tests in English in the future.
The tester used is designed for tests of medical equipment and this specific test proves that this specific HLK was safe. The problem is, however, that it does not prove anything with respect to the safety of other HLK's.
In the mean time, the same HLK is feeding a load of 730 mA. It's output voltage is 5.08 volts and the case temperature is Temp 
46.81 Temp F: 116.26105.
@Didi. You are correct. I work in a hospital. I will try to setup the Fluke to English.
Wait Mike, there is more ...
I sacrificed a device to the altar of success and opened it.
That was not very difficult. After scratching away some gum stuff the following was revealed.
I will try to remove the rest of the gum with acetone. I will also do some heat and burn tests.
This is quite funny to do
@Moshe. Yes they are. I did not yet dug into that, but is that good news?
I do not totally agree with this. When I take a look at the example circuit and read the ovp text, I can only conclude that the output is protected, because the circuit seizes to work when VCC rises to high. Whatever happens to the input circuit, I don't know. Therefore I prefer a fuse and and a varistor.
Have a look at the tutorial link text
I did not finish the automated power tester, but I put an HLK with a DS18B20 temp sensor in a closed flush box(is that the English word for the box in the wall, used for domestic wiring?).
A simple resistor acts as a load and draws a 800 mA from the power supply. That is 33% more than the max continuous value. Voltage across the leads is 4.96. That is 5.08 without load. Not too bad. At 600 mA (100% load) the voltage is also 5.00.
The Dallas says that the surface temperature at the HLK is 48.19 c ( F: 118.74).
Also do not forget to mount adequate capacitors to reduce ripple.
@petewill and @rvendrame ... Every country has directives regarding flammability. I cannot say which one is valid. I have seen some testing in the past. They put a burner under the device under test and waited to see what happened after removal of the source. In general (without any warranty whatsoever) when there are no flames or when they extinguish autonomic is good. If there is no hot material dripping from the DUT, that is also good. The test I carried out is described above. No dripping en self extinguishing. So I am satisfied.
Sorry, I cannot be more specific. I do not have the knowledge.
@rvendrame: yes the fuse in series in the mains live wire en the varistor in parallel with the primary side of the HLK.
With respect to the varistor ... see the sheet below:
Take a value that is well above the normal AC tension of your mains power, but below the max input voltage of the HLK. so in Netherlands 250 volts will do.
The specs of the unit states that it resilient to high voltages. I tested it with 250 VDC across input and output.
As stated before in this threat, the specs are ok, it only lacks the stamps.
From what I have seen so far, the module is good for me.
From the specs:
4.Safety CharacteristicsοΌ
4.1Products designed to meet UL, CE safety certification requirements.
4.2Safety and electromagnetic compatibility
Designed with the input of 0.5A UL certified insurance;
PCB board using double-sided copper clad plate production, material for the 94-V0 fire rating level;
Safety standards: Compliance with UL1012, EN60950, UL60950
Insulation voltage: I / P-O / P: 2500VAC
Insulation resistance :I / PO / P> 100M Ohms / 500VDC 25 β 70% RH
Conduction and radiation :comply with EN55011, EN55022 (CISPR22)
Electrostatic discharge :IEC / EN 61000-4-2 level 4 8kV / 15kV
RF radiation Immunity: IEC / EN 61000-4-3 See Application Note
4.3 Temperature safety design
At room temperature,the capacitors of this power , the inner surface of the main converter maximum temperature does not exceed 90 β;
Shell maximum surface temperature does not exceed 60 β
Well, I must say, I am very happy with the result. Thanks for the testing.
So, I am already planning to use it in a number of devices. To avoid too high temperatures in confined boxes, it might be a good idea to glue a temperature fuse to it and wire it in series with the live mains wire. When the temperature rises above, lets say 75 degrees celsius, the fuse breaks down.
Looks very nice, but you cannot use it for sensors or actuators that can be touched by hand and do not comply with the insulation standards, since parts of it will be connected to mains.
@petewill I think this is a wise decision.
I liked the discussion on this thread, so I have to thank you too.
Now it is waiting time. Waiting until the hlk-s arrive at the lab of the test guy.
My Chinese friend said, the package is on its way.
@rvendrame said:
@Atomfire said:
Not a big fan of soldering SMD components and I cannot find standard components, how essential is the 2nd fuse and varistor on the 5v side?
We are trying to make it as safer as possible... Assuming such modules will stay in a wall box, very close to wires and/or other potential fireable materials, we should try to mitigate risks as much as possible.
As I mentioned above --- This is DIY, also means 'risk it yourself'. Don't tell your insurance company
That is why I prefer to use fuses that blow, like the ones I mentioned earlier.
The resettable fuses also get warm. Can't wait for the package from Conrad to arrive. I am dying to do some further testing.
With respect to the brave HLK ... it is on for some three days and it is stable.
Short update ... yesterday I asked or Chinese friends from Alie to send a HLK module to our test friend.
I also did an insulation test with 1000 Volt. The test shows more than 1000 MOhm between ac and dc. So far so good.
@aproxx This is a different kind of notation, but when I look the device up in de Bourns catalog, I see it is rated for 250 Vac. That should be good.
@aproxx The only varistor I see in your list is 5.5 Volt.
@aproxx I would say that the 50 mA fuse is too weak. The HLK draws between 0.1 and 0.2 Amp and can surge 10 Amp. So, I think the 1A version is good for both situations input and output. The varistor is only good for the output.
One thing to consider though. This is also chinese stuff ... is it really safe or are we introducing a new problem?
@rvendrame said:
@Moshe-Livne said:
@rvendrame Considering cost of postage and logistics involved it would probably be cheapest to just order two units from Ali to him? its 8$ including shipping if i remember correctly
Yes, it makes all sense. The only downside is that if we buy all at same time probably he will get all from the same lot, but in my opinion it by far doesn't invalidate the testing.
So, myself, @Bertb , @Didi = 3 PSUs, better than 2. I will share with you both the ship-to address ok? Thanks a lot!
