Prusa i3 MK2 power consumption  

Prusa i3 MK2 power consumption

Greetings! First post, don't kill me.

Just wanted to put out a general PSA on some current testing I did today on my MK2, but first here is a general disclaimer:

The following is for informational purposes only. In this post I am only going to list observations that I have made. In no way is this information to be taken as advice for any projects you may consider doing in the future. I am in no way associated with Prusa Research or any of its parent or affiliated companies.

A few notes on how thing were measured: the very first thing I tested was voltage coming from the power supply. The reading was 12.05 VDC across all three sets of connectors. That being said the following results will be in amps, which at the end I will wrap up with a conversion to watts and a comparison to the rated output of the power supply.

Well, with that out of the way, here is what I have found and how I found it:

Using a multi-meter hooked up inline with the 12VDC line going to the printer (yes I know there are two separate lines, I will get to that) on the top connector (labeled PWR IN) I was able to get the following readings during various tasks and operations:

Upon initial power on the unit consumed 0.42 amps at idle.
Setting the nozzle to 100 degrees C resulted in a draw of 4.02 amps during the heating process.
After that, I turned the nozzle heat down to zero and ran a Z Calibration to simulate a bit of load on the stepper motors which resulted in a peak of 1.00 amp.
After the above tests the unit sat at idle at 0.74 amps.
I also tried to check the cooling fan speed but it was a negligible about of current draw so I'm not too worried about it.

After checking the current draw on the above, I swapped my wires around and measured the current draw to the heat bed:

(Also to note; when hooked up to the heat bed, I measured current draw during all other activities (nozzle heating, stepper motors moving, fans spinning) and no current was flowing until I turned the heat bed on)

When I turned the heat bed on (set to 50 degrees C) I saw 11.85 amps draw which slowly dropped to about 11.50 amps when the bed hit target temperature. At this point current dropped to zero, and then fluctuated between zero and about 8.00 amps to maintain the temperature.

So now with the raw numbers lets do some calculations:

With the nozzle drawing 4.02 amps
The motors drawing 1.00 amp
And the unit at idle drawing 0.74 amps we get a grand total of 5.76 amps. and to be on the safe side lets round that up to 6.00 amps.

Add our peak heat bed draw (lets round 11.85 amps up to 12 amps) we get a worst case scenario of 18.00 amps during heavy usage. Now multiplying our voltage (12) by our current (18), we get 216 watts. Anyone know what the power supply is rated for? 240 watts. (At least mine is.) This means for our "worst case scenario" we will be utilizing about 90% of the power supply's rated load.

In conclusion, I hope you find this information useful for whatever you need it for. Happy printing!