Recommendation for 24V, 4A DC supply to power a GPSDO - Page 1
Forum section: electronics / general

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 12:46:39 am
content: I have a GPSDO that I bought on eBay arriving soon. It requires a 24V supply that can output at least 4 amps. A switching supply is fine, as it's just going into a switcher inside the GPSDO. I tried buying one off of Amazon.com, but despite the 4.19A printed on the label, it wasn't able to output 4A, and dies shortly after hooking it up to a 6 ohm load.Can someone recommend a source and brand which is known to be good quality? I don't want another Wun Hung Lo brand piece of junk from some ethically challenged manufacturer.A sealed unit with power cord is preferred, but if that's too limiting I can add a power cord and rig up some sort of case for it.Thanks

author: Mr.B
author_rank: Unknown
timestamp: July 17, 2015, 12:52:55 am
content: I have always purchased big grunty supplies like that from Mouser...This is a 5A model.http://nz.mouser.com/ProductDetail/CUI/SDI120-24-U-P51/?qs=sGAEpiMZZMs2%252bVrH5rwl1hIC1abDBN%2fVxuw%2fHId4HznnIj5F%2f9s5WA%3d%3d

author: tautech
author_rank: Super Contributor
timestamp: July 17, 2015, 12:57:14 am
content: You might consider the unit in this thread:https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 01:09:39 am
content: Quote from: Mr.B on July 17, 2015, 12:52:55 amThanks, Mr. B. I didn't even think to check Mouser or DigiKey. I'll just grab one with a barrel connector from there.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 01:12:57 am
content: Quote from: tautech on July 17, 2015, 12:57:14 amHi tautech -That looks pretty handy, but I didn't see an actual link to where to purchase one. I need 110V as I am in the US.

author: tautech
author_rank: Super Contributor
timestamp: July 17, 2015, 01:39:03 am
content: Quote from: motocoder on July 17, 2015, 01:12:57 am4 pages in Google looking for a 110 VAC unit failed to bring one up, sorry, seems like they're all 230 VAC.

author: LA7SJA
author_rank: Regular Contributor
timestamp: July 17, 2015, 01:59:24 am
content: Is it just me wondering why a GPSDO needs 96VA (24V 4A)? I've heard of double oven OCOX but 96VA sounds like over-kill. My powerhungry rubidium standard uses only 34W peak under heating up (5 Min) and 24 VDC 11W (Steady State). So can someone Please enlighten me.Johan-Fredrik

author: edpalmer42
author_rank: Super Contributor
timestamp: July 17, 2015, 03:37:09 am
content: Quote from: LA7SJA on July 17, 2015, 01:59:24 amThat's my fault. The internal power converter is labelled "18 - 36 Volts, 1.9 Amps".But since the question has come up, I decided to do what I should have done in the first place and measure the current. There are two similar units. One has GPS, the other doesn't. I powered up the GPS-equipped unit and found that at turn-on, it's power requirements are 18V@1.5A, 24V@1.0A, or 30V@0.9A.So, Motocoder, the power supply you've got might do the job after all unless when you said it died you meant 'permanently died'. Looks like 24 volts at 2.5 - 3.0 amps is enough to power both units.Sorry for any inconvenience.Ed

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 04:23:03 am
content: Quote from: LA7SJA on July 17, 2015, 01:59:24 amYes, it's just youSeriously, it does seem like a lot. It's a Lucent doubly redundant unit, so there are actually two ovens to run, which is I guess why it's so much. However, edpalmer42 measured his, and it seems like 3A is plenty to power both units.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 04:25:15 am
content: Quote from: edpalmer42 on July 17, 2015, 03:37:09 amThanks, Ed. The other unit is dead now (probably an internal fuse). It had an annoying whine anyway, and it costs me nothing to return it, so no worries there. But I will adjust my criteria on Mouser and get a unit that supplies a bit less power if that will save a few dollars.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 04:55:18 am
content: Quote from: tautech on July 17, 2015, 01:39:03 amThanks for looking. I found what I think is the same unit on eBay, and the listing says 110/220V:http://www.ebay.com/itm/DC-Power-Supply-0-30V-5A-Adjustable-Variable-digital-display-Switching-110V-220V-/251956886769?pt=LH_DefaultDomain_0&hash=item3aa9ccfcf1

author: tautech
author_rank: Super Contributor
timestamp: July 17, 2015, 05:12:41 am
content: Quote from: motocoder on July 17, 2015, 04:55:18 amYes it appears to be nearly the same unit but a re-brand.110/230 VAC select switch at rear.Those I source have only the Banana socket outputs.I've sold ~ 30 of these 230 VAC without any issues, sure they are not a precision supply but they are hardy.Recently charged a 6V 12AH SLA using CV, peaked at ~1.9 A and charging rate dropped to ~200 mA a few hrs later. Fan never cycled.Even 24 V batteries (27.6-28.4 V) at full tit (~5.12 A) fan duty cycle is only ~ 50%.

author: edpalmer42
author_rank: Super Contributor
timestamp: July 17, 2015, 05:45:17 am
content: Quote from: motocoder on July 17, 2015, 04:55:18 amThat looks like it would be a good bench supply, but I wouldn't buy it just to power the GPSDO. It's much too good for that. Also, you don't want to use a variable supply for a device that's going to be continuously powered. You just want a generic 24V power supply. Something like one of these:http://www.ebay.com/sch/i.html?_nkw=24v+3a+%22power+supply%22+universal+-led&LH_PrefLoc=2I haven't purchased any of them, this is just to give you an example.Some top-level brand names you can look for are Lambda, Power One, Delta, LH Research, Acopian, Mean Well, ACDC, Sola, etc. Another source is power bricks for printers, scanners, etc. 24 volts is too high for most laptop bricks, although I've seen more than a few at 19 volts. Maybe your local used computer store has something interesting. As has been mentioned, Digikey, Mouser, Newark, and Allied are other sources.By the way, I just hooked up both units. At 24V, slightly over 2 amps at turn-on and slightly over 1 amp after warm-up.The 10 MHz test point is 10.000 000 00 MHz as measured on my Rb-referenced counter. I've never tried this before, but if I use my counter's math function to get better resolution, the frequency seems to be high by maybe .001 or .002 Hz, but that might change after it settles down more. I think I'll let it run overnight.Ed

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 17, 2015, 06:14:50 am
content: How about use a quality aftermarket laptop PSU? They're typically 20V at 3-5A and will work nicely for your application.

author: Vgkid
author_rank: Super Contributor
timestamp: July 17, 2015, 04:15:45 pm
content: If you want to run a linear power supply ebay "hd24 power supply" they are industrial power supplies.

author: mojoe
author_rank: Frequent Contributor
timestamp: July 17, 2015, 05:19:23 pm
content: I bought one of the Lucent two-piece GPSDOs off ebay a while back. I am powering it with a Meanwell RSP-100-24 that I bought from Mouser for $37.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 05:42:41 pm
content: Quote from: mojoe on July 17, 2015, 05:19:23 pmAmazing coincidence - after discussing with some folks at work, someone recommended Meanwell. I found this unit at Mouser, for the same price you mention:http://www.mouser.com/ProductDetail/Mean-Well/GSM90B24-P1M/?qs=%2fha2pyFaduh2q7CtTd8EGGkfX%2fUYwV226Bv9J1nk7oC4sHEKp6tgzA%3d%3dIt’s one of those enclosed bricks – like a laptop supply – which means I only need to adapt the 24V output connector and not mess with any mains wiring. It’s rated for medical use, which (at least for reputable brands) means the internals are built to a much higher quality standard.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 05:46:08 pm
content: Quote from: edpalmer42 on July 17, 2015, 05:45:17 amYes, agreed. I was actually interested in that as something I could recommend to people at work. There's a big community of "makers" here, and I thought that might be a reasonable option to recommend to people on a tight budget. I've been restoring old linear supplies as a hobby, so I certainly don't need one of those myself (a massive understatement)

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 05:49:22 pm
content: Quote from: edpalmer42 on July 17, 2015, 05:45:17 amOh, that's not much at all. Well, I ordered the MeanWell, which can supply 3.75A, so it should have no issues with 2A. One question that I had for you is about the power connector. From the picture on the eBay auction, the power connector seems to be a DB9 connector. Can you elaborate on how that's set up specifically? Half the pins tied to ground and have to +24V? Or it just uses two of the pins? Seems like an odd choice.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 05:53:44 pm
content: Quote from: NiHaoMike on July 17, 2015, 06:14:50 amThis is a great idea. Unfortunately, I tossed out the one old laptop supply that I had in one of my "must clean lab - need more room" purges last year. In any event, I found basically the same thing (one of those laptop power bricks) from Mouser for $35.

author: edpalmer42
author_rank: Super Contributor
timestamp: July 17, 2015, 07:05:49 pm
content: Quote from: motocoder on July 17, 2015, 05:49:22 pmYes, it's a DB9. Pin 1 is +24, pin 2 is ground. I don't know why they chose those connectors for power. I agree that it's odd.The only reference for information on these units is the (very long) message thread on the Time-Nuts mailing list that started last October. Here's the link:https://www.febo.com/pipermail/time-nuts/2014-October/thread.html#87274.It goes on for a couple of months off and on so make sure you've got a comfortable chair.I let the units run overnight. They're wandering around more than I expected (phase variations of +-90ns). I'll leave them running and see if they settle down. OCXOs tend to take a long time (weeks) to really settle down after being powered down for a long time.Ed

author: tautech
author_rank: Super Contributor
timestamp: July 17, 2015, 08:43:28 pm
content: Quote from: motocoder on July 17, 2015, 05:49:22 pmThey should be fine.IME they've been good, I've a couple of their 450W 24 V units supplying very light quesient loads, but also infrequently driving 24 V solenoids @~ 14A.Their SC & OL protection works just fine.

author: Kjelt
author_rank: Super Contributor
timestamp: July 17, 2015, 09:13:23 pm
content: Meanwell is pretty good.I prefer industrial built in supplies since then you can see what you get, which caps etc.I do choose myself often the tdk-lambda supplies, cheap huge MTBF specs and A brand caps.https://www.conrad.nl/nl/tdk-lambda-ls-100-24-acdc-inbouwnetvoeding-272-vdc-45-a-100-w-511829.html

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 09:43:35 pm
content: Quote from: edpalmer42 on July 17, 2015, 07:05:49 pmI did read enough of the time-nuts thread to see that the 90ns variation seems to be normal for these units. I didn't see anyone reply back and say they settled down, but perhaps I missed it. I was also really interested to see if there was a mod to make the sine wave output 10MHz instead of 15, or conversely to make the 10MHz output sine instead of square, but I didn't find that either.

author: motocoder
author_rank: Unknown
timestamp: July 17, 2015, 09:47:03 pm
content: Quote from: Kjelt on July 17, 2015, 09:13:23 pmThe reason I didn't go for the industrial design is that I didn't like the fact that the mains wiring is just attached to the outside of the case. It seems unsafe to have 110V hanging around just waiting for someone to bump into it. And to fix that, I'd then be having to find some sort of enclosure, and perhaps provide some sort of cooling. How do you deal with those issues?

author: Vgkid
author_rank: Super Contributor
timestamp: July 18, 2015, 03:48:39 am
content: I have one of the HD24-4.8A power supplies(made by many different companies) I believe it has a 3 pin connector

author: Kjelt
author_rank: Super Contributor
timestamp: July 18, 2015, 06:44:53 am
content: Quote from: motocoder link=topic=50857.msg712210#msYes you need an enclosure, enough to be found. Cooling if 24/7 full load yes else this thing has 85% efficiency so you loose a few watts on heat, no problem. Your enclosed ps is also plastick it also has to loose heat? A few small holes in the enclosure top and bottom suffice.