Anet A8 Power supply cover w\LCD power meter

by papinist, published

Anet A8 Power supply cover w\LCD power meter by papinist Feb 5, 2017
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I was looking for a power supply cover since the day I bought this wonderful 3d printer, because I don't like the exposed contacts and the lack of a main power switch.
In the meantime I decided to add something to monitor power consumption when printing, because... well mainly for fun :D

At first I bought a DC power meter but since power in DC is well beyond 10A I had to buy a bulky DC power meter, and it won't never fit the tiny space under the power supply. Also, I was thinking about using all the three pairs of DC outputs so measuring that way is not possible.

I then found a cheap AC power meter from china that was perfect.. the only problem was that due to size it will not fit again under the power supply. The only solution was to design my own power supply cover.
I took inspiration (for an artist it means copying) from many other projects here on Thingiverse and I added mine as a remix of those. Thanks for your great work guys!

This is the cool 'n' cheap power meter I used, I paid about 7 dollars for it:

I also used an IEC socket with O\I lighted button, found at a local electronic fair but you can find on ebay easily.
In the next section I'll try to show you how to wire them up.

PLEASE NOTE: I have the first version of the Anet's power supply, marked 250w. I believe the 240w has the same size so it would be ok too, but probably not on the 180w version (if it exists).

A small video showing the LCD and some other mods I have (OctoPrint and relay board in action)

Check out all my Anet A8 projects:

Print Settings


Anet A8 (Prusa i3)






0.2 mm




Even if Simplify3D creates supports under the diagonal part under the display, in my many tries I discovered that this isn't really needed. The only support needed is the one on the left side, where the cable from the Z-axis motor will go through. You need to place supports manually there, at least with Simplify3D.
Look at the screnshot I uploaded to better understand.



Wiring this is really easy.
Wires go from IEC connector to the switch, and then to the AC IN connectors on the power meter. Then from it two wires go to the power supply IN connectors.
Look the pictures below to better understand.

I just uploaded a hand-drawn schematics - it's not a piece of art but should clarify the simple wirings needed :)

LCD AC power meter


Picasso's hand-drawn schematics with wirings

From IEC connector to switch, to power meter

Almost done

All connected

Installing on the power supply

I used an allen key screw I had as a spare that come with the printer, it's an M3 screw about 47mm long. Simply remove the screw near the "L" header and screw it in. The new screw you have left now can be used on the right side :)

How I Designed This

Designed with Autodesk 123D Design

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the wireing you posted doesnt make sens :S

Why is there a cable from L to pin 1? so if its in off position its briging the load cables but also still connected to L why? ( if you have a faulty switch it will burn out or the fuse.

sould it not be , N to (one of) load cable and L to pin 2 and pin 3 to (one of) load cable.

Your setup deosnt make sens to me, why sortcut 12 (load cables) and still be connected to L?

Huh, cool looking but what useful information does knowing the input power give you?

There could be some useful information... but actually I just use it as a cool looking gadget :)

Hi, I'm very, very new to this and I just got my printer this week. I'm trying to print as many things as I can. Please help me to understand how you can print this without supports. The only slicer I have is Cura 2.6.2 and you can't designate what gets support and what doesn't. At least I don't think you can. Like I said, I'm very new to this. It seems that the meter area is very large to go unsupported. Won't it sag?

It will sag a bit but you will remove the sagging part with a cutter\xacto knife and you save a lot of time and plastic without support :)

OK. Thank you for the quick reply. I'll give it a try and let you know how it turns out.

Hi! Could anyone provide a version which is just 98mm wide? I'm asking because me and Autodesk 123D are still enemies, and it seems I just can't get it right. My time & filament's running out!!! :-)

Thanks in advance.

Hi, I want to do this thing for my A6, 2 mosfet and power supply 12V 33A 400W, please, would someone be so kind as to tell me how is connecting the cables to the LCD?
Thank you

Hola, quiero hacer ésta cosa para mi A6, 2 mosfet y fuente alimentación 12V 33A 400W, por favor, alguien sería tan amable de decirme cómo es la conexión de los cables a la LCD?

Jul 12, 2017 - Modified Jul 12, 2017

An elegant design and a very funny quip: "I took inspiration (for an artist it means copying)".

Also, excellent step-by-step instructions.

Thank you! :)

Do I need any additional screws? If yes, which ones? Awesome design! Thank you very much!

The front screw is a spare long screw I found with the printer. The side screw is the front screw I removed from the power supply to insert the long screw :)

Jun 30, 2017 - Modified Jun 30, 2017

Thanks Mate for these nice Mod.
I'd load up a "Made" Picture for the public with a English/German Deskription.
Which Fuse to take ? i did took 16A fuses because 20A Fuses are hard to get, fitting the DC Power Plug and 20A max Display.
Measurement of Fuses was a Problem too and i ordered fat ones, not fitting first.
Now i started to collect Fuses not on my own will, so please Edit the Description with measurement of Fuses because they wont be iclusive with your described DC Power Plug i'd order.
(i would like to send you a more Professional wiring Map for Public use.)

Why you want to use a 20A fuse? Fuse is on the AC side, not DC, and AC barely reach 1A. You could probably use a 2A fuse, or 1,5A to correctly protect the printer. A 16A fuse on the AC side will never blown :)

Jun 30, 2017 - Modified Jun 30, 2017
FelixKiste - in reply to papinist

Measurement of them pls for public... There are a few differnt ones,,, i still ordered a whole set in case of no need included shipping and anger after :D

I left in it the one provided with the power switch, but it is probably overrated.

I wired the switch in and had it all working then when i wired in the display the fuse blew in the switch and the power supply blew. Is there a fuse inside the power supply or do i need to get a whole new one? If so, does someone have a link?

I dont supose any one would be willing to remix this for a diferent power supply ... specificaly.. https://www.amazon.com/gp/product/B007K2H0GI/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 ... I love this project and already have it wired up and working.. but this one even made a bit bigger wont fit the power supply properly.. so its just sitting there un mounted at the moment..

Pardon me if my question is stupid as I might be lacking some understanding. But don't we need a DC meter since we're measuring DC voltage? Like this one, that has a range of 0 to 50A: http://www.ebay.ca/itm/LCD-DC-6-5-100V-20A-50A-100A-Combo-Panel-Display-Volt-Amp-Power-Watt-Meter-/332182273215?var=&hash=item4d579b3cbf:m:mFd4dGoSkLGjjWRH5-mjDQQ

Apr 18, 2017 - Modified Apr 18, 2017
papinist - in reply to corsara

If you are measuring AFTER the power adapter, yes, since it transforms the 220\110V AC to 12V DC. So measuring after transformation requires the meter you linked. At first I thought about measuring DC, but that meter comes with that bulky resistor bar and a difficult wiring scheme, so I reverted to measuring AC.
In my project I'm measuring AC power, BEFORE the power adapter - the 220\110V AC coming from wall outlet. The benefit is a simplier wiring scheme, no bulky resistors and the actual power consumption of the printer. In fact, measuring DC, we will miss the power percentage wasted inside the power adapter by transforming AC to DC.

Oh, got it, thank you for the explanation, now I understand! Ok, one more question: is measuring the AC current (before the power supply) indicative to what current is going from the power supply towards mainboard and mosfet? I'm mainly concerned with monitoring what current goes through that wire.

If you are concerned with the current going though a specific DC wire, I recommend getting a current meter. The simplest of them have a plastic clip section that goes around the wire and will tell you the current running through it from induction. I always find it is better to err on the side of safety with larger wires, especially since you aren't running that far at all. I have 2 runs of 14 awg wire coming from the power supply to the mosfets for the heated bed and hot end. Then the included 18 awg wire powering the board. That should be more than sufficient without having to worry about current. Though getting at least one mosfet or relay for the heated bed is definitely recommended. Heed the advice of the other users who have had fire issues powering everything through the mainboard.

Yes of course it is indicative even if not 100% accurate due to the percentage wasted in transformation. (we need to know the power adapter efficiency to get the exact numbers but I bet it is in the 80-90% range)
For example I can see that with only raspberry ON my power consumption is 0.06A @ 220V AC, If you know something about electronic formulas (and I'm not one of those guys) you can do simple math to have the A @ 12V DC.

Excellent, thank you for the info! Conveniently, there are calculators online for the lazy people like me, like this one: https://www.batterystuff.com/kb/tools/ac-to-dc-amperage-conversion-run-through-an-inverter.html


Very nice model, can you send me the CAD model for some upgrades?, like add two switchs
thx for all

Hey Lazarides, I've just uploaded the .123dx file from Autodesk 123D Design. Please share your results! :)

Thx a lot off but i can edit it whit solidworks or autocad.

You can probably convert it in some way.. I found a tutorial to import it in Fusion360

Thx when i Finish the model i will shere it !
Thx again!

Crazy genious )))
Thanks for your upload. Will use it for my printer. Keep on

Thank you! Glad that my design is useful for others :)

to bad this don't fit the 30A power supply but it looks nice ... nice work

i have a question about the wiring. All i could find was a IEC unit with a 4 pin switch. (Model KCD1) Can you advise on how I would wire this.
Thanks alot

@johnqpyro I had the same question and finally found this write-up linked below. Hopefully it helps you too. I believe @papinist is correct that it breaks both the hot and neutral side of the AC connection. I am used to wiring up DC switches myself which usually only have 3 pins. I am guessing the light in the switches that we have are AC powered so thus the 4 pins.

I don't know if 4 pins are used to break both live and neutral wires, so I can't be of help.

How are you powering the Pi?
I've ordered a small AC-DC 5v 3A, to power the Pi, so that it can always be on and switch the printer PSU on and off like yours.

At first I used a wall power brick like the one for charging smartphones. Now I have a small 12-to-5v 3A DC-DC converter on a separate 12v line, and it works great!

The 12v is not coming from printer PSU?

Yes, it's only that my english is not so good :) I used three different pairs of wires coming from printer PSU: one going to raspberry thru this converter, one goes to the mosfets and the last pair is for the mainboard via a 2-channel relay board (the second relay is not used yet, I plan to connect some led strips)

Ok, so the switching relay is between the PSU and the printer, i somehow assumed the relay was between the mains and the PSU. I'd like the PI to be turned on all the time so that (hypothetically) i could start printing while i'm still at work. Is it a good idea to have the printer PSU powered all the time? If it's not very efficient then it will just be heating the house, an i suspect it's not very efficient at very low currents.
What was the current with printer off and PI on?

The printer PSU is not powered all the time, it is on only when I manually switch the switch on the back. In this way I can have all off, only the Pi on or all on.
Only the Pi on uses about 0.07A at 230v AC.

Ok but that sort of defeats the purpose of turning it on and off remotely if you still have flick the mechanical switch.
I think the goal should be that it works like a paper printer - always on in some sleep mode but turns itself to full power when needed.

Sure, for that you can keep the mechanical switch always on.
You don't want printer psu powered all the time, but you want to print remotely so something should be on - like a paper printer. Also regular printers has a 'mains' that you will keep on ON position, then ther printer goes to standby. Think at this the same way: switch on ON position, raspberry is powered and ready to listen to your commands, either local or remote, to switch on the printer and start printing.
Pi uses only a few milliamp when it is doing anything.

BTW trust me, you will never start a print remotely. You will need to check start and first layers in person to ensure all is good :)

If you shutdown the printer, the meter shutdown to? and erase everything? have a memory?

When shutting down the printer (via relay board controlled by Octoprint's menu) the meter is still active to monitors the raspberry's power consumption. When shutting down the main power (via the rocker switch at the back) the meter goes off but it has memory and keeps in memory the total W used.
You can of course reset this counter via long press on the only button available. You can also set an alarm if W used exceeds a specified amount - but I don't think this is of any use in this application :)

Thanks! Can also set the cost of kWh? to show the consume cost?

No, you can't.

Just uploaded a video showing the LCD and some other mods I have (OctoPrint and relay board in action)

I like it!

Well done!

Thanks SatorCodex :)

This is awesome. Could you provide a plan how you connected everything?

Thanks! It is really simple, I posted some pictures at the bottom of the description but if these are not enough I could make a simple pen drawing :)

I would really appreciate if you could make a drawing. I have the same plug with button and got the same voltmeter laying around. But i dont know how to connect everything.

I just uploaded a hand-drawn schematics - it's not a piece of art but should clarify the simple wirings needed :)

Aug 25, 2017 - Modified Aug 25, 2017
Jhinta - in reply to papinist

the wireing you posted doesnt make sens :S

Why is there a cable from L to pin 1? so if its in off position its briging the load cables but also still connected to L why? ( if you have a faulty switch it will burn out or the fuse.

sould it not be , N to (one of) load cable and L to pin 2 and pin 3 to (one of) load cable.

Your setup deosnt make sens to me, why sortcut 1&2 (load cables) and still be connected to L?