Hello All,
Alden pointed this power supply out to me this morning. I thought I would share.
http://www.mpja.com//productinfo/19149%20PS/
We have not tested it yet, but from the specs it looks like a very good choice for driving TinyG.
TinyG Power Supply
Can anyone please give rules how to choose a power supply for grbl shield ?
I am recommended at least 4.2A at 24V but not know why. I am going to use 3 steppers similar to this
http://www.sparkfun.com/products/10846.
Thanks
4.2 Amps at 24 volts for those motors should be just fine.
- Alden
Alden,thanks for your reply.I know 4.2 Amps at 24 volts should be OK. But can you please let me know how can I calculate that it should be just fine? I do not know why I am advised to use 24V and 4.2Amps.Why I can not use less amps and volts?Thank you for the reply.
Riley,
Thank you for the link.
This seems that it is a very nice all-in-one package for a reasonable price.
I intend to test TinyG with an ATX PS for the 5V and a laptop powers supply for some 19V @9amps. This has the advantage of being free for now but I may be interesting in upgrading at a later time.
Bonus question : I was wondering, why is the 5V from the USB not used ? Would it draw too much current ? Would it be possible to cut another USB cable to bring the 5 V to TinyG or would it still be too weak ?
Cheers,
Fabrice
It's actually a good idea to use the USB 5v, it was just not part of the design. The 5v is actually regulated down to 3.3v for use on the board. The RS485 adapter uses 5v directly, but the rest is all 3.3v. The total current draw is about 100ma, which is well within the limit for USB. It's a good idea we should consider in any future hardware revs.
Thank you Alden.
In this case, do you think I could solder 2 wires from the female mini USB connector to the +5V input?
I was hoping to receive my board today and play with it during the weekend but it has not made it yet...
If you like I can take a look at this (probably sometime this afternoon, US EDT) before you start messing with it. I don't know what would work without studying it. I believe there are some subtleties regarding the FTDI chip. Also, If something blows up, I have other boards; you don't (but we would appreciate your business :)
- Alden
Well noted. I'll keep to the standard way first while you carry out the experiment then :)
This seems so simple that there has to be a catch...
lol... Nice idea.
Riley
Is it really possible to use grblshield v2 with ATX power supply( 12V) only when using these stepper motors http://www.sparkfun.com/products/10846 ?
Thanks
You can use an ATX supply with +12 and +5v (assuming you have done all the right things with the power-on switch lines, voltage sense lines and loading as required). There are plenty of articles on the interwebs about how to convert an ATX supply into a "bench power supply" that address these issues. One caveat: I have had trouble using power supplies harvested from a particular generation of Dell desktop - so be careful if the PS originated in a Dell.
Using 12 volts for the motors works fine. Using 24 volts just works better, regardless of the type of motor. Most of the Reprap world uses 12v and is quite happy with it.
has anyone had success with the 5v from usb idea?
I still haven't tried it, but would like to. You should be able to wire pin1 of the USB port over to the 5v input of the power connector. Perhaps through a ferrite bead. The grounds are referenced the same, so that should be OK. If I recall correctly the board consumes about 80 ma, so the 100ma limit on USB at plugin should be OK. I will need to check the current draw, wire it up, cross my fingers, and turn it on. Now that I have an idea of what to do let me see if I can get to this in the next day or so.
- Alden
I've done this. I ran a wire to a switch, and then from the switch over to the 5V line where it comes into the terminal block. This way I don't bypass any of the capacitance along the way. It seems to work fine for me, though I haven't done too much testing yet.
Back to TinyG Support or the forum archive.