Motherboard Power Alternative

Heya fellow RepRapers

I recently got my hands on a 12v 2a power supply that has a secondary 5v 2a supply. I would like to hook up the 5v to my Motherboard v1.2 so that I can unplug my laptop without killing the power on the Mother board.

I'd like to know if there are any reasons why this would not be possible or if it is, then where exactly can I wire / solder the power to the Motherboard.

Thanks!

Les.

This is my motherboard.

2A is sufficient for one stepper motor, but not for 4 or 5. PC PSUs run independently from the host computer, but how would you send G-Code, then? Some firmwares claim to have SD card support, but I'm not sure wether this is ready for public consumption, yet.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

Thanks for your reply Markus.

The 2gb SD card support is exactly why I got this motherboard. I was told that that's exactly what it's for, although I haven't tested it yet.

The Amps... So what would you say is the min-max? I've heard 8a is ideal, but I'm finding it hard to find 8a so please advise a min-max that you think is realistic.

And yeah. Should the SD card work, then I don't want my PC stuck running all night, so I need to find out where to wire the power in and if 5v 2a is ok at all.

Nochmals vielen Dank,

Les.

Quote

I've heard 8a is ideal, but I'm finding it hard to find 8a

About every PC power supply matches this specification. Salvage one from an old Pentium III PC and you're set.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

the one i am using now is a old AT PSU it is working nicely for me, once i got the load resistors setup for it, i have found it to be allot less trouble than trying to get a ATX one to work for me. i think this comes down to RTFM more than anything on my part though. that and i seem to have bad luck trying to get some things to work.

---

[mike-mack.blogspot.com]

Traumflug Wrote:
-------------------------------------------------------
>
> About every PC power supply matches this
> specification. Salvage one from an old Pentium III
> PC and you're set.

Thanks again Markus. Will do.

Now I just need someone to tell me what v / a is best for the separate powering of the Motherboard and where to wire it in. I really don't want a pc running all night when I have the 2gb sd card in place.

2 amps for each stepper motor, 5 amps for the extruder heater, 10 amps for a heated bed. There is no difference between running it with the host PC on or off.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

The motors take a lot less than 2A at the supply rail and most extruder heaters take less than 2A.

---

[www.hydraraptor.blogspot.com]

I agree with Nophead,

I run X, Y & Z steppers at 0.5A 1.5A
The extruder stepper at 1A 1.0A
Etruder heater 1.8A 1.8A
=====
4.3 A

Heated bed at 3A 3.0A
=====
7.3A

Maybe add 200ma for CPU, drivers, LEDS

7.5A with heated bed 4.5A without a heated bed.

Infact on X and Y its only 0.4A as they are only 400ma steppers.

I'm using two setups both using the Gen3 Electronics.

Each setup has 4 of the 2.3 stepper boards and one Gen3 1.1 motherboard.

Edited 1 time(s). Last edit at 06/07/2011 02:40AM by BodgeIt.

---

Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

My point was that if you run a stepper at say 1A it does not take 1A from the PSU. The chopper drive acts as a step down converter, so the current at the supply is less by the ratio of the supply voltage to the motor voltage.

If you set the reference voltage to give 1A the worse case with 2 coils on is 2 x 1A / sqrt(2) = 1.4A. The typical motors are rated 2.8V at 1.65A, so at 1A they will be 1.7V motors. The the average current at the supply will be 1.4 * 1.7 / 12 = 0.2A. This is theoretical, in practice various losses will mean the current is a bit higher, say 0.3A.

---

[www.hydraraptor.blogspot.com]

My point was from my experience you don't need to run them with a 1A driver setting per winding; in the first place let alone 2A per winding. I think setting these very high coil curents could be why there are somany Pololu drivers being cooked/blown up. I am still using the old stepper drivers I will be trying out Pololu drivers soon. So I may have to increas the current slightly to accomodate micro stepping mabe as much as a 25% increase.

You are absolutly correct as to how you calculate the overall curent measured at the power source your answer matches the question better than mine.

---

Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

I tend to run mine as high a current as I can without the drivers or motors getting too hot. That is in the 1 to1.5A range.

The higher the current the better the positional accuracy is and less chance of missing steps due to the nozzle catching on plastic that tends to curl upwards when printing overhangs.

---

[www.hydraraptor.blogspot.com]