Unisource Power Supply PS-3305U ... 2x 30V 5A USB Programmable ... a $372 deal? - Page 1
Forum section: electronics / testgear

author: dmytty
author_rank: Newbie
timestamp: March 05, 2015, 07:20:43 am
content: I have been looking for a higher current power supply for Brushless DC motor testing (amongst other things). After a massive search (GW Instek, etc), I came across this potential match in the form of the Unisource PS-3305U, which is a 300 watt power supply:http://www.testequipmentdepot.com/unisource/powersupply/ps3305u.htmOK, so it's not high precision (from the panel anyways but USB?). However, it looks nice, no? Coarse fine adjustment, output switches, memory, CH3 voltage options, reverse polarity, OTP....Despite this thing looking nice to my eyes, Google returns nothing more on this power supply than a link to a precious few sellers and perhaps some Facebook postings by the manufacturer. No user stories or mention anywhere.The only similar product I came across on EEV Blog (or really anywhere) was a circa 2011 discussion of a Vantek single channel supply which may have similar manufacturing origin as Unisource:https://www.eevblog.com/forum/reviews/vantek-dps-3305p-32v5a160w-programmable-dc-power-supply/30/Someone else on EEV Blog also mentioned a prior Unisource P6100 as a possible high current $300 power supply candidate:https://www.eevblog.com/forum/chat/vantek-power-supply/msg60630/#msg60630Tech Depot helpfully mentions that the P6100 referred to has been replaced by the PS-3303U, which is the 3A version vs the 5A version I'm looking at:http://www.testequipmentdepot.com/unisource/powersupply/p6100.htmI did track down the manufacturer, but not much other information is available. I called the California office of Unisource, spoke with a nice Korean guy. He told me that Unisource was the old LG Labs, and this particular power supply origin is China. Regarding some technical points, he wisely asked me to email him, and I also received an email back confirming floating grounds.I also read through the manual on the Tech Depot site, and found some other information:Although the front panel is 3 digit only, the user manual refers to commands that make it seem possible to set voltages and currents to 5 digit resolution. For example, from page 16 of user manual:VSET1:20.345Sets the CH1 voltage to 20.345VIt also seems that reading current and voltage might update in 70 ms or so (VOUT<X>). This polling refresh rate would seem much faster than the linked to Vantek model which only returned current and voltage readings 1 time per second.I really am trying to get 5A per channel while sourcing a decent enough supply. Anyone know anything about Unisource or even this particular power supply?If I was content with 3A I would be happier buying the Siglent SPD3303D which has been exhaustively covered on EEV Blog. However, I'm hoping that this Unisource could be a quality supply with higher power output.****** A discussion on paralleling separate power supplies ******I did have some discussion with Siglent (emailing with engineers back in China) about the ability to synchronize 2 of their power supplies via USB. I also contacted Rigol about doing the same for the DP832. It seems something could be done, but nobody 'advises' doing this.I did confirm that there are no reverse current protections on any of these power supplies, so I would have to create a little output protection circuit to ensure that a voltage variation would not make magic smoke. My understanding is that could be based on Schottky diodes (at about 630 mV voltage drop), or maybe using the smart bypass diode of the TI SM74611 (only 26 mV drop @ 8A!).http://www.ti.com/product/sm74611From a voltage drop perspective, the TI would be nice, but that's limited to 30V (they recommend 28V max), so that would seem to be cutting it too close(?) Also, it seems that the TI also have the effect of increasing capacitance on the output, perhaps by just 102 pF though(?)Anyone doing something to increase current with the Sigent 3303 or Rigol 832?

author: Awesome14
author_rank: Regular Contributor
timestamp: March 05, 2015, 08:33:57 am
content: When I want current, I use TDK-Lambda linear VDC supplies. A few months back I picked up a Lambda LK-351: 0-60V; 0-15A, both metered. The meters in digital power supplies are not that good. I always wind up connecting a real DMM, which is probably the least expensive means to obtain accurate readout. The supply I mentioned is a top performer, but it's a simple linear design. The meters are analog. And it's heavy. 100 lbs, ~45kg..But it has overvoltage protection, voltage or current limiting capability, remote sense, + or (-) ground, parallel or serial integration with up to 3 additional units for up to 240V at 15A, or 60V at 60A. The unit is rated to sustain a complete short across the output, at maximum power, indefinitely. I accidentally draped a braided thermocouple lead across 2 bus-bolts, for 12 hours, with the PSU current regulation maxed out! But it didn't damage the supply.From no load to instantaneous full load (15A) produces only a 50uV output-voltage change! The supply is rated at +-0.015% regulation. But my observation was +-0.0045% at 10VDC with 120 Ohm load. You can pick the units up on eBay for 200.00USD including shipping. In the nineties they sold for 17,000.00USD / unit. But you can't dial in the output. You have to use an accurate meter to set an accurate output value.I connected a 2.3 OHM, 900W resistor to the unit, cranked it up, and after 20 minutes it didn't show the slightest sign of fatigue. On the back there are cooling fins. This is perfect to set a few 60mm fans for added cooling, which I have done on mine. The unit is made in industrial-gothic style, very dark green with lots of cold rolled steel. The chassis is 3/16" solid steel. The US government is selling off many of these units.If you think you could make do with a unit like I've described, check it out. But it isn't programmable except in the most basic sense that it can be controlled by a remote resistor. The LK-350 is a 36V; 25A version of the LK-351 mentioned here. I have one of those too.

author: dmytty
author_rank: Newbie
timestamp: March 05, 2015, 09:47:33 pm
content: Your power supply is a beast! Do you have that in a thread? Would be nice to see some pics, video ... a mini review.However great that supply, that is more power than I can budget space and weight for. Would be interesting to use that ability to maintain a short indefinitely for electrolysis.Still interested in the Unisource feedback. Order is on hold but should ship tomorrow unless I get bad feedback from here.

author: 3DTronics
author_rank: Newbie
timestamp: June 30, 2016, 02:46:11 pm
content: Old thread but I'm also interested in this power supply. Looks like you ordered it, what are your thoughts on it?