Ways to power a large series of Wemos D1 mini boards

Hardware
62

For devices in your garden far from where you could reasonably run power.

I've used this circuit for remote devices to charge batteries from a solar panel. It's ridiculously simply and works like a charm. He uses a phone battery, but I've used it with protected 18650 cells and 5 volt and 6 volt 150-200 mA solar panels from aliexpress.

3 Likes
63

If you're not driving particular loads and you are on the range of 200mA you can simply usa an UTP cable and bring 12v (I recomend you to place a fuse of 500mA in the beginning, as the cable may be cut/broken in future you are not going to "cook" it and replace it all after), near the little bastard place a DC/DC converter or a simply small voltage regulator module with 7805 or similar chips. It depends just on the current

2 Likes
64

Many people don't understand the purpose of fuses. Fuses and circuit interrupters protect UPSTREAM.

In this diagram, the fuse protects the power supply.
e4cc4589d1df5e40653245f5e4305925d85a1f5d_2_690x172

If there is a fault in the cable, a shovel cut, for example, the fuse removes that cable from the circuit to protect the power supply. The fuse does not protect the cable or any device connected to it.

1 Like
65

In our context in Australia we have RCDs/RCBOs - they are designed to protect the cable from overloading - so they will trip and stop supplying current above their rated level - which is deliberately sized to be lower than the cable.

This stops people inadvertantely plugging in too much load into the wire and melting them/settings fires.

Similarly the integrated RCBO version also protects against common ground faults, earth leakage, shorts (from whatevever cause - be it a shovel ! etc)

So they do in the case of AC protect the cable

In DC (say a car) they are also sized in the same way to protect the cable in the case of a higher power level power supply (such as the battery)

Craig

66

It's fair to say that most 'modern' power supplies (including phone chargers) have built in overload/short circuit protection that shut down the supply if necessary, so no need for a fuse.
Just need to check the specifications...

67

I beg to differ. This is an important safety requirement.!!!

As mentioned by myself and others - Each cable needs to be fused at the PSU end, at a rating LESS than the cable, and not more than the maximum required for the device on the end.

Say you have a 30A psu, feeding lots of devices. The cable to each device may only be rated at a few amps.

In this case the cable could catch fire before the PSU shuts down.
If the device or something connected to it has a fault, then a suitable sized fuse will blow and protect this also.

1 Like
68

So if a fuse is an important safety requirement, why don't phone chargers have a 'hardware fuse'?
Phone charger cables get trapped in drawers, chewed by dogs, etc.

Modern power supplies are designed that way.

I would however use a fuse upstream from the power supply, ie the mains supply side.

71

Paul,

I have no desire to offend anyone, argue over semantics or start some kind of flame war!

As such I will not comment further on this topic. :laughing:

But we should be aware that there will be many people reading these posts, who may take anything posted here as the best practice.

When it comes to potential life safety you cannot be TOO careful. :cry:

I have many decades of experience installing low voltage electronic security equipment. I can tell you that all reputable companies would install DC power along the lines I have outlined, for the reasons I mentioned.

If you take the example I gave of a 30A PSU, powering multiple low power devices along many separate cables rated for 1A. I would not want to see how hot the cables get while wating for the 30A PSU to trip out, if there was a fault at the far end.

PS any good quality phone charger will have a none-serviceable fuse internally. :crazy_face:

DISCLAIMER: If in doubt seek expert advice !!

3 Likes
72

Me neither!
Lets agree on your last sentence and move on;

2 Likes
73

Don't be so modest!! You guys are my personal experts :wink:. Moreover, I don't think I can find somewhere advice for less money than here :rofl:

I am learning from all these discussions, so the main objective is already accomplished!

2 Likes
74

So have you got a Wemo online yet .......... ?

75

Hoho, I am not that fast. I also had to search and order all kind of stuff based on all feedback I got.

Online not yet no. But with a huge pile of assistance from @dynamicdave and @zenofmud I managed to build a prototype that sends ultrasonic distance values to Node-RED:

IMG-20220203-WA0001
IMG-20220203-WA00011920Ɨ1080 323 KB

Hopefully I find some free time next weekend to continue with this...

5 Likes
76

And now the fun begins, I do enjoy playing around with these :wink:

Happy to help if needed, I have tried connecting just about everything possible.

2 Likes
77

Incorrect. Please go and read up on this before sharing information that is simply wrong and potentially dangerous should someone follow your advise.

Indeed.

This bit you got right, but not for the reasons you think. Fuses protect cables.

Incorrect, the fuse does indeed protect the cable, it ensures that the current demand cannot exceed the safe rated capacity of the cable, and thus prevent fire.

2 Likes
78

This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.