Arduino Forum

Using Arduino => General Electronics => Topic started by: heyarn on Oct 13, 2012, 04:46 am

Title: connecting 2 powersupplies in parallel
Post by: heyarn on Oct 13, 2012, 04:46 am
hi everyone!

This will probably be easy:

I'm building a 3d printer, and I currently have a 360W power supply hooked up to my arduino which is hooked up to ramps 1.4 (http://reprap.org/mediawiki/images/6/6d/Rampswire14.svg). The problem is that my heat bed is draining too much energy. (like after a minute of operation, the led's go off)

Anyway, I thought I might solve the solution by hooking up the power supply to a smaller power supply (its actually a 100W 12 V laptop charger) in parallel. I think it would work, but I want to make sure that there is a small to no risk of frying my electronics.

Will it work? :)

Title: Re: connecting 2 powersupplies in parallel
Post by: tjbaudio on Oct 13, 2012, 05:21 am
Short answer no, you will fry stuff.  The two PSU will not be matched and will fight, one pulling up, one pulling down.  Best case you can combine them with low impedance balancing resistors but that's not really a good way for mismatched units and is less efficient.  In your case you should find a bigger PSU or split up the loads to different supplies if possible.
Title: Re: connecting 2 powersupplies in parallel
Post by: MarkT on Oct 13, 2012, 01:56 pm
Actually it depends on the power supply - some will fight, others will simply fail to co-operate (the slightly higher voltage one will do all the work).  In general connecting PSUs in series or parallel will not work - they are not like batteries in this respect.
Title: Re: connecting 2 powersupplies in parallel
Post by: jrmcferren on Oct 13, 2012, 03:29 pm
Use a separate supply for the heaters (connect the grounds of the supplies together though). Use transistors on the outputs to operate the heaters. If you aren't using PWM, you can use relays instead if you wish.