Reviews:
 ·T-Mobile US
| DC Power Supply Voltage Question I often seen 12v pieces of equipment using higher voltage power supplies (like 13.5 volt). Is there a particular reason to do this other than a long cable run. In all cases I've come across this the power run has been 6' or less.
In one case, the manufacturer recommended supply is a 13.5VDC, 4.4A power supply. The equipment runs on 12volts. The cable run is short (6 feet) and the the unit only pulls 0.9AMP @ 12VDC.
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| Not sure what kind of 'equipment' you're talking about, but many things that run from 12V will have a voltage regulator inside that converts 12V to whatever is needed such as 5V, 3.3V, 1.8V, etc.
If the equipment actually needs 12V, then taking the voltage drop across the regulator into account can come out to about 13.5V.
How did you come up with that 0.9A @ 12VDC? Is that measurement or spec?
Telling us what kind of 'equipment' you're talking about may be helpful to figure out the reason for that recommendation.
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| reply to nightdesigns
It's an AMX Netlinx controller.
0.9A @ 12VDC is spec
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TheMGPremium
join:2007-09-04
Canada
kudos:2 | reply to nightdesigns
If the unit has internal voltage regulators for the internal voltages that it needs, then the external power supply voltage is not critical and anything within the operating voltage range of the regulators will work.
Then the equipment manufacturer just picks a power supply from an OEM manufacturer. Maybe the 13.5V power supply was slightly cheaper than the 12V ones, who knows. |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
1 recommendation | reply to nightdesigns
said by nightdesigns:often seen 12v pieces of equipment using higher voltage power supplies (like 13.5 volt) Please do some more digging ... 12V power supplies are everywhere while regulated 13.5V power supplies are quite rare.
Adjustable output 12V power supplies are often used to get 13.X volts output for lead-acid battery charging.
said by nightdesigns:In one case, the manufacturer recommended supply is a 13.5VDC, 4.4A power supply. The equipment runs on 12volts. They probably chose 13.5V/4.4A to allow battery charging since equipment needs less than 1A.
If their equipment really needs exactly 12V ... applying 13.5V may cause problems even with a 6ft wire. Most "12V" equipment can handle 10V-14V range because people may use a "12V" lead-acid battery to power such equipment. |
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| said by lutful:If their equipment really needs exactly 12V ... applying 13.5V may cause problems even with a 6ft wire. Most "12V" equipment can handle 10V-14V range because people may use a "12V" lead-acid battery to power such equipment.
This could the one the OP is referring to: »www.amx.com//assets/dataSheets/N···heet.pdf
This is an embedded computer with a bit of other stuff, and the computer portion is guaranteed to not run on 12V.
The relays and serial port may use +12V directly, but they shouldn't be to picky about it up to 15V. The equipment should be good at least up to +15V, but depending mostly on caps and voltage regulators/heatsinks, possibly up to 18 - 24V.
Personally, I would just use a simple 12V 1A wall wart and check for current and/or voltage drop, and change PS if it drops too much.
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
1 recommendation | said by aurgathor:said by lutful:Most "12V" equipment can handle 10V-14V range because people may use a "12V" lead-acid battery to power such equipment.
This could the one the OP is referring to: » www.amx.com//assets/dataSheets/N···heet.pdf... the computer portion is guaranteed to not run on 12V. ... The equipment should be good at least up to +15V, but depending mostly on caps and voltage regulators/heatsinks, possibly up to 18 - 24V. ... Personally, I would just use a simple 12V 1A wall wart OK, I looked at the datasheet and have a few comments:
a) The "computer part" ... the "NetLinx ICSNet Communication Network Card" obviously requires the 12V/900mA specified in datasheet.
b) It is dangerous to assume that a 12V embedded system can accept 15V. Many 12V DC-DC regulators specify maximum 14V input.
Linear regulators (unlikely on such a PCB) would tolerate 18V-24V ... but the heat sink may not handle 5-12W power dissipation to output 12V/900mA.
c) Even though the controller uses only 900mA ... a 12V/1A power supply will not be enough because the system has an "AxLink Port: 4-pin 3.5 mm mini-Phoenix (male) connector that provides data and power to external control devices" in addition to RS232 and other ports. |
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 SparkChaserPremium
join:2000-06-06
Downingtown, PA
kudos:3
 ·Verizon FiOS
1 edit | reply to lutful
said by lutful:They probably chose 13.5V/4.4A to allow battery charging since equipment needs less than 1A.
If their equipment really needs exactly 12V ... applying 13.5V may cause problems even with a 6ft wire. Most "12V" equipment can handle 10V-14V range because people may use a "12V" lead-acid battery to power such equipment.
Agree, the voltage is just too close to a PE12V4 battery.
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"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The good thing about science is that it's true whether or not you believe in it." - Neil deGrasse Tyson |
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| reply to nightdesigns
said by nightdesigns:I often seen 12v pieces of equipment using higher voltage power supplies (like 13.5 volt). It depends upon the equipment, for example professional video gear, camcorders, decks, lighting and wireless receivers are considered 12 volt devices, but can be run with voltages as high as 17 volts, the primary reason for this is to allow those devices to be powered with a rechargeable battery pack that has a high enough voltage rating to fully utilize the capacity of the battery pack before it drops below what the equipment needs to operate.
A second reason is the use of such equipment under conditions where commercial power is not available and the equipment will be powered off a vehicles electrical system which can have large variances in voltage.
As for 13.5 that is a common voltage in the pro video world, I have a number of 4 pin XLR power supplies that are rated for 13.5, as that level of voltage is high enough to prevent a low voltage shutdown during the power up of say a 50+ watt camera mounted lamp. |
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Reviews:
·T-Mobile US
| reply to nightdesigns
I'm familiar with the voltages for TV equipment (11-17 volts typical) since I work in television. This particular piece of equipment is for fixed installs.
The only thing I can think of is that the manufacturer power supply runs about $125.00. The equipment works fine on a 12v 1amp supply for a few dollars. Everything AMX is ridiculously expensive.
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| said by nightdesigns:manufacturer power supply runs about $125.00 ... equipment works fine on a 12v 1amp supply for a few dollars. All those ports and relays require extra current ... the datasheet shows even a 6A power supply option.
You can buy decent quality laptop power supplies for $10-$25 range. This one is 12V/6A: »www.amazon.com/Sabrent-AD-LCD12-···00VE7GQQ |
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 HankSearching for a new FrontierPremium
join:2002-05-21
Burlington, WV
kudos:2 | reply to nightdesigns
You have received a lot of good response. Not sure if they have made any production changes to this power supply and it has been awhile since I have purchased any. But they are not terribly expensive and you can open them up and adjust the voltage if necessary.
»shopwiscomm.com/Astron-RS-3A-3-A···odLiEAvw |
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| reply to lutful
said by lutful: b) It is dangerous to assume that a 12V embedded system can accept 15V. Many 12V DC-DC regulators specify maximum 14V input. But when the manufacturer's PS is rated 13.5V, using a DC regulator with a 14V max input would be a very poor design.
c) Even though the controller uses only 900mA ... a 12V/1A power supply will not be enough because the system has an "AxLink Port: 4-pin 3.5 mm mini-Phoenix (male) connector that provides data and power to external control devices" in addition to RS232 and other ports.
quote:
The only thing I can think of is that the manufacturer power supply runs about $125.00. The equipment works fine on a 12v 1amp supply for a few dollars.
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| reply to nightdesigns
said by nightdesigns:The only thing I can think of is that the manufacturer power supply runs about $125.00.
For a 13.5V 4.4A PS?!?! 
!@#$%^&*()!]!
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 SmokChsrWho let the magic smoke out?Premium
join:2006-03-17
Saint Augustine, FL | reply to nightdesigns
said by nightdesigns:I often seen 12v pieces of equipment using higher voltage power supplies (like 13.5 volt). Is there a particular reason to do this other than a long cable run. In all cases I've come across this the power run has been 6' or less. Primarily this is a throw back to automotive equipment. Where 12V really means something from 12V on up to around 15V, most commonly 13.8 to 14.5. |
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HankSearching for a new FrontierPremium
join:2002-05-21
Burlington, WV
kudos:2 | reply to Hank
Just received this from MCM this morning. It may be of interest.
»www.mcmelectronics.com/product/7···n=DD1394 |
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SmokChsrWho let the magic smoke out?Premium
join:2006-03-17
Saint Augustine, FL | If the OP is actually looking for a supply, I just found »www.powergatellc.com/ and they seem to have very good prices and a wide selection of power supplies. I ordered several of the meanwell LED supplies and got them quickly. FWIW I don't see any reason the CV "LED" supplies couldn't be used for just about anything.
Here's one that looks like it's pretty much fits the OP requirements »www.powergatellc.com/mean-well-g···ply.html |
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