Voltage Quest

General discussion of 3D printers

Re: Voltage Quest

Postby cvoinescu » Thu Dec 20, 2012 1:16 pm

I took a different approach and I've been very happy with my choice so far: I use a 24 V power supply.

I changed the heater resistor in my hot end from 6.8 ohm to 25 ohm. I don't have to worry about cable thickness now (the current on that is only 1 A), and even the heated bed draws a reasonable current. I modified a standard PCB heated bed from four traces in parallel to a series-parallel arrangement of four times the resistance simply by cutting one of the side traces in the middle and soldering the supply wires on either side of the cut. It now draws 6 A at 24 V when cold, down to 5 A when hot, which is easily manageable.

Edit: The only downside is that the fans still require 12 V, but a step-down DC-DC converter rated at 3 A can be had on eBay (from China) for less than $3.
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Re: Voltage Quest

Postby kbob » Thu Dec 20, 2012 6:04 pm

cvoinescu wrote:Edit: The only downside is that the fans still require 12 V, but a step-down DC-DC converter rated at 3 A can be had on eBay (from China) for less than $3.


Fans, plural? If you have two fans, you can wire them in series from the 24V supply...
Bob
"If you didn't code it, it will never own you." (-:
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Re: Voltage Quest

Postby cvoinescu » Thu Dec 20, 2012 7:38 pm

kbob wrote:Fans, plural? If you have two fans, you can wire them in series from the 24V supply...


Not really. Firstly, they're different sizes, secondly, I want them controlled independently, and thirdly, even if they were the same size and I wanted both to run at the same time, if one gets stopped accidentally, it suddenly presents a lower impedance, so the voltage drop on it goes down, and the other one gets the brunt of the 24 V supply. Not something I want to try. The series thing works well only with some types of loads (light bulbs, resistors, capacitors in AC, some types of high-voltage rectifiers, etc) but not with variable loads (electric motors, most electronic circuits, anything with a thermostat, etc).
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