Need advice for my first project: TinyG controller box

Hi guys. New member here. I’ve been trying to get into CNC machining for several months now, and for various reasons I seem to keep hitting one wall after the other.

Perhaps the biggest problem is that I just don’t know very much about electronics; I’m actually a computer programmer so the idea of being able to program a machine to bring the ideas out of my head into the the real world appeals to me greatly, but I just don’t have very much knowledge or experience with the finer points of electronics.

I’ve been trying to get the TinyG working, but somehow managed to burn out my power supply. Well, after finding the clear and easily understood instructions for connecting the TinyG to the QuietCut spindle, I went ahead a bought a bunch of stuff from Inventables, including both a 48V power supply (for the spindle) and a 24V power supply (for the TinyG). I am currently drawing out schematics for a control box to neatly and safely house everything.

However, it just occurred to me that I might not need to use the the 24V power supply at all (yeah, I know, pretty obvious in hindsight), and leaving it out would significantly reduce the size of the box (and perhaps somewhat reduce the complexity of the wiring). I can see two possible ways of doing it, and I’m not sure which one is better - or if either is even safe:

1)I plan to include several computer fans in the case - one for the TinyG and one for each power supply. If I use two 12V power supplies and wire them up in series with the TinyG, drawing off the 48V power supply, that would avoid the need for any extra hardware. However, I’m not sure if that would provide the TinyG with an appropriate and stable supply of power?

2)The second option I see would be to get a DC-DC converter. A quick internet search revealed a number of large units and a few small ones. This would take up more space and probably generate more heat, plus cost more and require more waiting time (everything takes a long time to reach me where I live). I guess I would use it to power to both the TinyG and the computer fans (two fans in series again). This seems to be the less desirable option, assuming the first option is actually feasible.

The other alternative of course is just to use the 24V power supply as I had originally intended. In this case I will run two computer fans in series off the power supply itself, and a third will go off the TinyG’s own computer fan power supply pins.

So my question is to the members of this forum is, can I safely wire the TinyG in series with two 12V computer fans to an Inventables 48V power supply? If so, are there any “gotchas” I need to watch out for? If not, what do I need to look for in a DC-DC power supply, and can anyone recommend a very small one that will fit my needs?

Thanks for the help everyone, and sorry for being so long-winded!

No. You’re likely to destroy the GShield and/or something connected to it. Fans do not regulate voltage. They only supply an amount of resistance/impedance. Thus you should think of them as “Rated For” 12V, not that there’s some way they know or can do anything about the voltage supplied to them. Since those motors take large amounts of current, and the fans don’t, I would suspect that the vast majority of those 48V would affect the GShield, and in significantly less than 12V would go through each of the fan. If the GShield voltage > 30V, bad things can happen.

If the fans are the exact same I’d wire them in series. That’d probably work, and worst case scenario, you’re out two fans. Likewise, I’d think your two 12V power supplies in series would work just fine, so long as they can provide enough amperage to run the motors (I’m not sure what that number is, but I’d take the inventables number and use that. Since they’re in series, the amperage supplied by each of the two 12V supplies should be equal to the number of amps of an equivalent 24V supply (i.e. don’t divide or multiply by two here – you want the same number or greater).

Or as another alternative you could probably just get 24V fans?

Thanks for explaining it to me. So I’m definitely not going to wire the fans up in series with the TinyG!

I guess I’ll just go ahead and use the 24V power supply despite how large it is; the control box is just going to have to be bigger than I’d hoped.

I’ll check out the local suppliers to see what my options are in terms of computer fans and decide whether to go for 24 or 12 volt fans based on size/strength etc, since it seems that either should work.

So, after my first post I’ve been looking at the BeagleBone (specifically the Black wireless version). I’ve ordered one to play around with; I’m hoping to just put it inside the controller box so I don’t need to have my laptop wired to the machine while carving. It looks like that should be doable; I believe Chilipepr runs on the Beaglebone after all. I would appreciate any advice from anyone who’s actually used a Beaglebone and/or TinyG though.