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Author Topic: Can I run 12V computer peripherals from my 13.8V Astron?  (Read 973 times)
NB7B
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Posts: 3




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« on: July 29, 2019, 11:19:01 AM »

I also posted this in computers and software, but this may actually be the most appropriate place for it.

I'm getting back on the air after many years away.  I'm currently getting S9 noise on the rig with an indoor antenna (will be an outdoor antenna soon).  I crawled under the desk and counted nine 12V wall warts. Unplugging them reduced the noise about to about S4.  With anything designed for ham use, I don't hesitate to use my 13.8V Astron linear power supply.  Is anyone successfully using 13.8V to power 12V computer peripherals, USB Hubs, External HDD, Ethernet switches and the like?  I have an RS-50M, so I have plenty of headroom.  If need be, I could always add another Astron (12A?) and adjust it down to 12V but, would rather not if I don't have to.

Thanks in advance,

de NB7B
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KB7TT
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Posts: 58




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« Reply #1 on: July 29, 2019, 12:04:40 PM »

Do it all the time here in the shack.  LED light strips, remote antenna switches, etc.  No problems in 3 yrs.
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NB7B
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Posts: 3




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« Reply #2 on: July 29, 2019, 12:15:28 PM »

Thanks, that's all I needed to hear.  Thank you for taking the time to reply.

73 NB7B
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AA4PB
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Posts: 15067




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« Reply #3 on: July 29, 2019, 01:26:09 PM »

There's a difference between "LED light strips, remote antenna switches, etc." and "USB Hubs, External HDD, Ethernet switches and the like". The computer devices are likely to be more sensitive to over voltage. You could use two silicon diodes in series between the 13.8V supply and the computer device. The diodes will drop 0.7V each, leaving 12.4V applied to the device. Make sure you use diodes rated to handle the maximum current of the device.
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Bob  AA4PB
Garrisonville, VA
K0UA
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Posts: 4828




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« Reply #4 on: July 30, 2019, 02:46:59 AM »

Measure all the wall warts.  I bet a lot of them may be close to 14 or even 15 volts.  Just because it says 12 volts on the "wart" does not mean it really is 12 volts.

Also it would be a nice practice to build a little box with fuses for each device appropriately fused for its current draw so you can isolate and protect the wiring.  It might seem like a lot of work, but you would really appreciate it if something starts drawing a lot of current for some reason.  It would sure help your troubleshooting instead of just looking for puffs of smoke  Smiley
« Last Edit: July 30, 2019, 02:50:28 AM by K0UA » Logged

73  James K0UA
ARRL Missouri Technical Specialist
K7MEM
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Posts: 724


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« Reply #5 on: July 30, 2019, 04:59:47 AM »

I also posted this in computers and software, but this may actually be the most appropriate place for it.

Well then, as I posted in the other forum, "how much do you value your peripherals?".

All of those peripherals should have a manual that specifies the expected voltage and voltage tolerance. It's common to have a +/- 5 percent tolerance. But 12 volts to 13.8 volts is around 15%. Going above the tolerance may not bother the peripheral, but you won't know until the smoke comes out. That's a little to late.

I like the two diode idea from AA4PB the best. That will keep the voltage within tolerance.
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Martin - K7MEM
http://www.k7mem.com
W9IQ
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Posts: 3555




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« Reply #6 on: July 30, 2019, 05:15:00 AM »

If you go this route, read a bit about Thevenin connections. Despite the regulated supply, the voltage along the wires is bouncing around quite a bit due to high transient currents. Well implemented Thevenin connections can help avoid problems.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K1CJS
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Posts: 6283




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« Reply #7 on: July 30, 2019, 10:33:56 AM »

Measure all the wall warts.  I bet a lot of them may be close to 14 or even 15 volts.  Just because it says 12 volts on the "wart" does not mean it really is 12 volts.

Also it would be a nice practice to build a little box with fuses for each device appropriately fused for its current draw so you can isolate and protect the wiring.  It might seem like a lot of work, but you would really appreciate it if something starts drawing a lot of current for some reason.  It would sure help your troubleshooting instead of just looking for puffs of smoke  Smiley

If you do measure them, best measure them under load, not while they're not connected to their respective powered item.  Under 'no-load' conditions, they will measure more voltage than they will under load.
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AA4PB
Member

Posts: 15067




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« Reply #8 on: July 30, 2019, 10:47:12 AM »

One of these would be a convenient way to distribute the power with each device individually fused:
https://www.amazon.com/WINDCAMP-Connector-Distributor-Compatible-Powerpole/dp/B01KBTF7C0/ref=sr_1_13?hvadid=78340301981482&hvbmt=be&hvdev=c&hvqmt=e&keywords=west+mountain+radio&qid=1564508316&s=gateway&sr=8-13
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Bob  AA4PB
Garrisonville, VA
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