Possibility of powering Sanguinololu via standard DC power brick?

I was thinking… the Sanguinololu is so nice and tiny, it seems like a real shame to hook it up to a big honkin' computer PSU that'll be half the size of the printer itself. I've been thinking about alternatives. A PicoPSU is an idea, but it's really meant for computers and it'll have the big motherboard connector as well as SATA and Molex connectors that I don't need. Really, I just want something I can plug into the board on one end and the wall on the other end. How do you guys feel about attaching a female barrel connector to the board and powering it with an AC->DC power brick? I can find all sorts of 'em on eBay and they go all the way up to reasonably high wattages. The problem has been finding a connector. I've found a few, but none of them are quite perfect. For example:

This would work, but the pins don't fit the holes in the Sanguinololu PCB: [www.cutedigi.com]

And this would be perfect if it had pins on the bottom: [www.cutedigi.com]

Basically, I'd like one of those connectors to be crossed with a standard screw terminal like this one: [www.cutedigi.com]

What do you guys think about this idea? I couldn't find amp ratings for these connectors, but do they look like they could stand up to 10 or more amps?

The power brick will work if you don't have a heated bed. You should be able to get by with 12V at 8 Amps. If you have a heated bed, then you'll need at least 18-20A. At that current, a PC power supply is cheaper and easier to find.

i have a makerbot powered by a 6 amp 20volt brick, the 20 volt goes directly to stepper drivers. i use 4 stepper drivers, and the extruder is stepper. 3 the drivers are the makerbot v2.2 1/2 steps driver, the extruder driver is the new board version i have set to 1/8 division.


you will want to have the stepper drivers get voltage directly from brick and not go thru the PicoPSU, here is the voltage pin-out of the molex connectors.
Pin # Color Function
1 Yellow +12 V
2 Black Ground
3 Black Ground
4 Red +5 V



before plugging cable in you will wand to cut the yellow wire and directly connect it to power supply input so it does not go thru picoPSU


also have a dc in jack for power supply, and also have a power on switch. these two are very handy especially when rebooting board, and connector is good for when moving machine around, easy to unplug.

Yeah, I have a Makerbot as well, but this doesn't seem to be the way things are hooked up in the Reprap world. Generally it looks like the stepper drivers get power from the board rather than directly from the PSU. Any particular reason? Is the MBI approach better?

I mentioned that I did it with makerbot, so you would know that it is possible and it works ok for there stepper drivers.

The polupo steppers claim handling to 35v, but I doubt it will do more than 24, as it will overheat very quickly. You will want to heat sink those chips above 12v.
Here is the product page for that [www.pololu.com]

Here is the Sanguinololu schematic http://reprap.org/mediawiki/images/8/83/Sanguinololu-schematic.jpg


Of course the schematic is that of the original version.

some of the issues you run into with running higher voltages are the extruder heater needs to have higher resistance, the steppers require constant cooling, and current is too much for an external regulator. The 5 volt regulator also will get hot with more than 12v going in.

So take your hot end resistance and make it R=12/V *current resistance V is current voltage used. 12 is voltage designed for and R is your heater resistance.

What I did on my makerbot was taking the parallel resistors and made them series. It works ok, but does take longer to heat up.

From the schematic above it looks like you will need an external 5v regulator to lower voltage down. This can be done with the picoPSU, using its Molex attachment; it should provide the 5v for you. I am not sure about the 12v out pin, I think it is whatever the input voltage is, but just clip the cable, and hook up the yellow wire to incoming voltage.

It looks like it is possible to run it with just incoming power and a 7805 voltage regulator as well. There are no on/off signaling pins that would necessarily require a pc power adaptor. It looks like all that is used is the Molex connector

also be sure to use a fan and preferably heat sinks on all stepper drivers, they should not blow, but they will turn of if over temping.

That being said. I have never built Sanguinololu, please verify with schematic.

Edited 2 time(s). Last edit at 08/30/2011 08:37PM by jamesdanielv.

jamesdanielv Wrote:
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> some of the issues you run into with running
> higher voltages are the extruder heater needs to
> have higher resistance, the steppers require
> constant cooling, and current is too much for an
> external regulator. The 5 volt regulator also will
> get hot with more than 12v going in.

I was under the impression that the advantage of using higher voltage/less current with a motor gives you a cooler running motor. Is that not the case?

Just thought I would put my two cents in.

My Repstrap is running of an old xbox 360 power supply and my recently finished Prusa is powered by an old playstation 2 power supply enclosed in [www.thingiverse.com] its 6.2A @ 12v and I have printed about 500g (1lb) of stuff with out any issues. I have also reached 250c and 400mm/s, but no heated bed.

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Quote

I was under the impression that the advantage of using higher voltage/less current with a motor gives you a cooler running motor. Is that not the case?

Voltage and current are not related with a constant current drive and affect the motor in different ways: -

* Less current certainly makes the motor run cooler but also reduces the torque at low speed.
* Increasing the voltage doesn't affect the torque at low speed, but it does make it fall off slower as speed increases.

So if you reduce the current and increase the voltage the motor runs cooler, has less torque but will keep that torque up to a higher speed.

Edited 1 time(s). Last edit at 09/25/2011 02:57AM by nophead.

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