View Full Version : Need a little help regarding using 2 PSU's

20-11-2017, 04:18 PM
Hi guys, my psu died this morning mid job and I dont have a replacement, but I do have 2 similar(not identical) 24v PSUs. Am I right in thinking I just need to connect them as usual(2 on 1 and 1 on the other)? Or do I need to connect grounds?


john swift
20-11-2017, 08:02 PM
assuming they are switch mode power supplies

when connected in parallel to get more current than any one can supply
the odds are only one power supply will supply most of the current

usually its the very expensive power supplies designed to be connected in parallel that will share the load

when connecting them in series to get 48V you could be lucky but,
it is likely that one will fail to start and be reverse biased by the working supply
this will damage the electrolytic capacitors on the output side of the non working supply


20-11-2017, 08:42 PM
Thanks, would it be possible to use 1 for 2 of the steppers and another for the Z axis(bigger motor)?

Thanks, Phil

john swift
20-11-2017, 08:45 PM
yes , that will be the best solution with what you have


20-11-2017, 09:13 PM
Do I need to connect grounds or anything?(both switch mode psus)

Thanks for the help!

john swift
20-11-2017, 09:37 PM
wire the mains live , neutral & earth to the power supplies L,E,N terminals

if the stepper drivers have opto-isolated step & direction inputs

you only need to connect the power supplies DC output to the stepper drivers DC power in

and the breakout boards step , direction & common (which could be either 0V or +5V depending on how you wire the stepper driver input)

what stepper drivers do you have ?

on some systems you may find the negative DC output connected to earth
(like a PC's AT or ATX power supply , [common black wires internally connected to earth])

did your original power supply have the negative output linked to the mains earth ?
if it did you can do the same with the two new power supplies


22-11-2017, 11:15 AM
I got them connected and working, thank you!

john swift
23-11-2017, 11:49 AM
great to see you have it working