MacSkyver, what did you use to draw that schematic? It looks professional. Thanks for the regulation circuit idea. I plan to look into that next.
I've been reading about voltage and amperage needs. Arduino MEGA operates on 5V and the recommended input voltage is 7-12V. Arduino's voltage regulator starts to overheat above 12V. Is the higher voltage output by an unloaded transformer going to fry the Arduino? RAMPS 1.4 can run on 12V and needs 5A for five steppers and two hot ends + 11A for heated bed. This number matches the MakerFarm Prusa 8" i3 minimum amperage of 16A.
I worked out an example of a linear regulated power supply. Start with a 120VAC to 16VAC transformer at 6.25A (187F16) connected to a full-wave bridge rectifier rated for 15A and a forward voltage drop of 0.67V (SBR15U100CTL-13). This leaves me with 15.33V. Add a 0.01F capacitor rated for 50V (ECO-S1HA103EA). Ripple is now I/CF= 5 A / (0.01F * 240hz) = 2V. Is this ripple acceptable? Add the LM338 linear regulator with resistors, protection diodes, output capacitors, and a fuse for the transformer. The regulator is rated for a maximum of 5A. I now have to power the heated bed separately. At 5A, the dropout voltage is about 2.75V. So I think I can expect to get 12.58V of regulated DC out of this power supply. The heat output of the regulator is (2.75V + 0.58V) * 5A = 16.65W. At R_thJA = 35C/W, that is a 583C increase in temperature. Which is well above the 125C long term stability temperature. Is it feasible to dissipate ~17 watts via a heatsink? Edit: Could the waste heat be used to heat a printer bed? Perhaps the regulator sits below a copper bed, or a heat pipe is used to transmit heat to a fixed-bed printer (delta-type).
I am starting to see why switching power supplies are superior to linear regulators. Especially at higher currents. Maybe I will build a small one as a bench power supply at low current.
I've been reading about voltage and amperage needs. Arduino MEGA operates on 5V and the recommended input voltage is 7-12V. Arduino's voltage regulator starts to overheat above 12V. Is the higher voltage output by an unloaded transformer going to fry the Arduino? RAMPS 1.4 can run on 12V and needs 5A for five steppers and two hot ends + 11A for heated bed. This number matches the MakerFarm Prusa 8" i3 minimum amperage of 16A.
I worked out an example of a linear regulated power supply. Start with a 120VAC to 16VAC transformer at 6.25A (187F16) connected to a full-wave bridge rectifier rated for 15A and a forward voltage drop of 0.67V (SBR15U100CTL-13). This leaves me with 15.33V. Add a 0.01F capacitor rated for 50V (ECO-S1HA103EA). Ripple is now I/CF= 5 A / (0.01F * 240hz) = 2V. Is this ripple acceptable? Add the LM338 linear regulator with resistors, protection diodes, output capacitors, and a fuse for the transformer. The regulator is rated for a maximum of 5A. I now have to power the heated bed separately. At 5A, the dropout voltage is about 2.75V. So I think I can expect to get 12.58V of regulated DC out of this power supply. The heat output of the regulator is (2.75V + 0.58V) * 5A = 16.65W. At R_thJA = 35C/W, that is a 583C increase in temperature. Which is well above the 125C long term stability temperature. Is it feasible to dissipate ~17 watts via a heatsink? Edit: Could the waste heat be used to heat a printer bed? Perhaps the regulator sits below a copper bed, or a heat pipe is used to transmit heat to a fixed-bed printer (delta-type).
I am starting to see why switching power supplies are superior to linear regulators. Especially at higher currents. Maybe I will build a small one as a bench power supply at low current.