RAMPS 1.4 24v 15A power supply

Hi everibody... i was searching how to turn my ramps 1.4 shield from 12v to 24v. that is allready checked but i my problem is that the shield run with 11A in one port and 5A the other one and my power supply gives 15A. i dont know if i can just connect directly ´cos my higher demand is 11A or if it will burn....

Are you sure?

a 12v system with standard parts is 11amp and 5amp (130watt bed, 40 watt hotend+ steppers + electronics)
but a 24v system with a 24v bed is 5.5amps and a 24v hotend and the rest is somewhat less than 5amps ( still 130watt bed, 40 watt hotend etc)

use the useful calculator [www.rapidtables.com]
enter any 2 values, it will fill out the rest
eg a 24v bed is normally 4.4 ohms, plugging in 24v and 4.4 ohms gives 5.45 amps.

Edited 1 time(s). Last edit at 07/31/2018 11:28PM by Dust.

The 11A and 5A circuits are the maximums that those are fused for, and not the amount of power needed. your system will need from the power supply whatever they need, and if it's more than the fuse will take then the fuse will go. The fuse will also go if it needs to protect the board from a short circuit, of course. (At least we hope that it will.)

Assuming that you're replaced the thermal fuses that the RAMPS board comes with, and whatever lower voltage components (16V capacitors etc) as well as removing the diode to supply voltage to the arduino, you should be able to run power from your 24V supply to both of the inputs without additional problems. My 24V heated bed is rated 250W, so that's a little over 10A. 50W for the hot end heater, is about 2A, leaving about 3A from a 15A supply. With my motors having 2A capable drivers, that might be running a little close to the line.

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

If you want 24V for the bed only you don't need to change anything on the ramps board, just use 24V on the 11A capable input. Just use a separate 12V psu for the 5A capable input. My 3d printr works like that for 3 years, even with a 12V bed, I set the maximum duty cycle to 128 in marlin as to not trip the 11A fuse. 24V at 50% duty cycle is basically the same as 12V current wise.

If you want 24V for the steppers without modifying the step stick you do need to make sure you have 30v+ capable fuses, capacitors and make sure to remove D1 as it will power the arduino at 24V if left in place. The 1117 regulator can only take 15V max so will burn up at 24V. You still need a 12v psu/buk converter for the arduino, or connect the usb port to a psu.

Another option is to remove the stepstick Vmotor pins and solder them separately to 24V psu.

A 15A psu is more than enough. Nema17 Stepper motors rarely draw more than 1A. If you'd put 2A on them they'd get rather hot and will affect performance.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

@imqqmi

Incorrect.

On most ramps the 11amp polyfuse is also rated for 16v max, so you have to change it, or it will over heat and trip lots.
There is the odd rare ramps that does come with a higher voltage 11amp polyfuse, though personally I have never seen one. (I would like to know the part number)

As it happens I own one that is rated for 30V. The part number is 30uf900. But you're right if the polyfuee is rated at 16V it needs to be replaced with one such as mine or a car fuse rated at 11A. I think when I set the bed temperature to 95 it will trip and consequently trigger the firmware runnaway protection. I think I'll set a maximum duty cycle at say 80% and see what happens.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]