DC Adapter question

On Tue, 07 Jun 2005 17:25:44 GMT, "Ann-Marie"
wrote:

I just moved from the UK to the US. I brought my Wireless access
point/router with me, but I need to get a new DC adapter for it so that it
works on the 110V supply here.

You could just get a 117VAC to 220VAC stepup transformer. You
probably have other devices that run off 220VAC.
http://www.starkelectronic.com/st500.htm

It says on my UK adapter that the output is: 7.5V DC 1500mA 11.25VA

It would also be helpful if you would disclose the maker and model
number of your wireless access point and router. The problem is that
the sticker label is NOT what the unit draws. The voltage is probably
correct, but the current drain of the router may be considerably less
than the current rating on the transformer. It would be easy enough
to measure the current drain of the router with an amps-guesser and
size the power supply accordingly.

Every universal adapter I find that has 7.5 as an option, seems to have a
current rating of either below, or above the 1500mA I need. They are usually
either about 1000mA, or 1700mA etc.

I don't like the universal adapters (the ones with a switch from zero
volts to more than enough to blow up anything if you goof). I've
confiscated those from customers before they blow up their laptops and
electonic devices. Actually, the usual problem is not the voltage but
the polarity of the connector. Getting it backwards is all too easy.
About 3-4 times per year, someone drifts into my shop with a blown
something and a universal replacement adapter. Not recommended unless
you glue the switch and plug adapter in place.

Does anyone know if this is a required rating, or if it will automatically
only take the current required, as long as it's set to 7.5V ?

More current is always a safer bet. If it says 1500ma on the adapter,
then 1500ma or larger will do just fine.

For example, if I get the one with only 1000mA rating, will it not work?

1000ma might work if the access point draws less power. The typical
access point (no router or switch section) burns about 8 watts. At
7.5VDC that's about 1000ma. However, without measuring the current
drain, this is pure speculation on my part.

Another problem is that if it actually does work at 1000ma, it might
be running at near its maximum rating. That's a problem because the
limit is set by iron core saturation which results in gross
inefficiency, heating, and a small fire if left alone. This is
another reason why underrated power supplies are a bad idea.

If
I get the 1700mA one, will it be too much and blow the wireless access
point?

No. Only excessive voltage or reverse polarity can do any damage.
The access point will draw only whatever it decides to draw in
current. Having excess current capability will have no effect on how
much the access point draws.

Thanks for any help,
Daniel

Reminder... Since you're now in the colonies, kindly reset your
firmware to US regulations and standards. If it's not possible, see
if there is a replacement flash firmware from the unspecified
manufactory web pile.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
#
# AE6KS

Hi,
It's a D-link DSL-604+, it has built in modem, router, switch, WAP, so I
guess thats why it takes quite a lot of power.

I looked in the manual, and it says the power consumption is 12W max, which,
I worked out to be 1.6A at 7.5V - would that be right?

If I get this 1700mA adapter, and run it at 7.5V, is there a risk of fire or
anything? or is that only if I got a lower rated one.


"Jeff Liebermann" wrote in message
...
On Tue, 07 Jun 2005 17:25:44 GMT, "Ann-Marie"
wrote:

I just moved from the UK to the US. I brought my Wireless access
point/router with me, but I need to get a new DC adapter for it so that it
works on the 110V supply here.

You could just get a 117VAC to 220VAC stepup transformer. You
probably have other devices that run off 220VAC.
http://www.starkelectronic.com/st500.htm

It says on my UK adapter that the output is: 7.5V DC 1500mA 11.25VA

It would also be helpful if you would disclose the maker and model
number of your wireless access point and router. The problem is that
the sticker label is NOT what the unit draws. The voltage is probably
correct, but the current drain of the router may be considerably less
than the current rating on the transformer. It would be easy enough
to measure the current drain of the router with an amps-guesser and
size the power supply accordingly.

Every universal adapter I find that has 7.5 as an option, seems to have a
current rating of either below, or above the 1500mA I need. They are
usually
either about 1000mA, or 1700mA etc.

I don't like the universal adapters (the ones with a switch from zero
volts to more than enough to blow up anything if you goof). I've
confiscated those from customers before they blow up their laptops and
electonic devices. Actually, the usual problem is not the voltage but
the polarity of the connector. Getting it backwards is all too easy.
About 3-4 times per year, someone drifts into my shop with a blown
something and a universal replacement adapter. Not recommended unless
you glue the switch and plug adapter in place.

Does anyone know if this is a required rating, or if it will automatically
only take the current required, as long as it's set to 7.5V ?

More current is always a safer bet. If it says 1500ma on the adapter,
then 1500ma or larger will do just fine.

For example, if I get the one with only 1000mA rating, will it not work?

1000ma might work if the access point draws less power. The typical
access point (no router or switch section) burns about 8 watts. At
7.5VDC that's about 1000ma. However, without measuring the current
drain, this is pure speculation on my part.

Another problem is that if it actually does work at 1000ma, it might
be running at near its maximum rating. That's a problem because the
limit is set by iron core saturation which results in gross
inefficiency, heating, and a small fire if left alone. This is
another reason why underrated power supplies are a bad idea.

If
I get the 1700mA one, will it be too much and blow the wireless access
point?

No. Only excessive voltage or reverse polarity can do any damage.
The access point will draw only whatever it decides to draw in
current. Having excess current capability will have no effect on how
much the access point draws.

Thanks for any help,
Daniel

Reminder... Since you're now in the colonies, kindly reset your
firmware to US regulations and standards. If it's not possible, see
if there is a replacement flash firmware from the unspecified
manufactory web pile.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
#
# AE6KS

On Wed, 08 Jun 2005 00:12:09 GMT, "Ann-Marie"
wrote:

It's a D-link DSL-604+, it has built in modem, router, switch, WAP, so I
guess thats why it takes quite a lot of power.

True. The DLink DSL-604+ is not sold in the US. It does DMT ADSL so
it will probably work with most US DSL ISP's. Check with your local
DSL ISP to be sure.

I looked in the manual, and it says the power consumption is 12W max, which,
I worked out to be 1.6A at 7.5V - would that be right?

That will save me the effort of looking up the specs. Yep, 1.6A is
correct.
12 watts / 7.5V = 1.6A

If I get this 1700mA adapter, and run it at 7.5V, is there a risk of fire or
anything? or is that only if I got a lower rated one.

Nope. The rated current is where it will run forever without
overheating difficulties. Only the lower current drain adapters will
cause problems. However, just to be sure, check if the power adapter
gets unusually warm when you first plug it in.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
#
# AE6KS

"Kenny" wrote in message
...
Another solution is to get a 110V to 240V AC transformer, then you can use
your existing adapter.

-- Yup,i'm with Kenny on that one,thats what i did,works great.

Ann-Marie wrote:

Hi,
I just moved from the UK to the US. I brought my Wireless access
point/router with me, but I need to get a new DC adapter for it so that it
works on the 110V supply here.

It says on my UK adapter that the output is: 7.5V DC 1500mA 11.25VA

Every universal adapter I find that has 7.5 as an option, seems to have a
current rating of either below, or above the 1500mA I need. They are usually
either about 1000mA, or 1700mA etc.

Does anyone know if this is a required rating, or if it will automatically
only take the current required, as long as it's set to 7.5V ?

For example, if I get the one with only 1000mA rating, will it not work? If
I get the 1700mA one, will it be too much and blow the wireless access
point?

Thanks for any help,
Daniel


A supply could be rated at 1000A and work no differntly than one
rated at 1700mA.
It is the *voltage* rating that one must be cautious about.
Now, if there was a way you could measure the actual current drawn by
the unit, i would expect that it would draw less than 1500mA - perhaps
as low or lower than 1000mA.
If that were true, then you could use the less expensive supply.
However, in your case, it is wiser to use a supply rated at or more
than 1500mA.

Robert Baer, wrote:


A supply could be rated at 1000A and work no differntly than one
rated at 1700mA.

BWAHAHAHAHAHAAHAHAHAHAHAHAAH! You ****ing moron.

the actual current drawn

There's your contradiction, you ****witted ****.

Robert Baer wrote:
A supply could be rated at 1000A and work no differntly than
one rated at 1700mA.
It is the *voltage* rating that one must be cautious about.

Almost, but not quite. If a DC supply is significantly under loaded,
the voltage will rise. How much depends greatly on the design chosen.

For that reason it is probably not a good idea to use a supply
rated significantly higher than the original supply was rated
for... *if* the voltage actually makes any difference at all.

(But if, as is true with many wifi units, the onboard supply is
actually a switching power supply, which is basically
insensitive to input voltage, it simply won't make any
difference at all.)

Now, if there was a way you could measure the actual current
drawn by the unit, i would expect that it would draw less than
1500mA - perhaps as low or lower than 1000mA.

If that were true, then you could use the less expensive supply.

Bad idea. The supply has to be able to provide current at
*peak* usage. Trying to measure that can be very difficult, if
not impossible for most people. With a wireless radio, for example,
the peaks happen when the unit is transmitting and may be for very
short bursts. If you simply measure the current while the unit
is idle, what you measure is a totally misleading value.

However, in your case, it is wiser to use a supply rated at
or more than 1500mA.

Ah, you got that one pegged.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Kenny" wrote in message
...
| Another solution is to get a 110V to 240V AC transformer, then you can use
| your existing adapter.


Transformers are recipical devices so a US adaptor (240 to 110) can supply
240 from 110 by reversing the connections just make sure you have a
transformer and not a ballast reduction. In this case likely won't hurt
anything it just won't work.

The router will draw the current that is correct. You need to match the
voltage to within about 1 Volt. The rating of the adaptor is the maximum
safe load it can handle. You can use the 1700 ma one, as long as the voltage
is correct.

If you were to read up on ohm's law and understand it, you would understand
the answer to this.

A simple explanation, is that your AC outlet in the average home (In North
America) can supply 15 Amps at 120 Volts. Very few of your devices use more
than 1 or 2 Amps. The only exceptions are the air conditioner, toaster,
microwave oven, and the electric kettle, just to mention a few.

--

JANA
_____


"Ann-Marie" wrote in message
...
Hi,
I just moved from the UK to the US. I brought my Wireless access
point/router with me, but I need to get a new DC adapter for it so that it
works on the 110V supply here.

It says on my UK adapter that the output is: 7.5V DC 1500mA 11.25VA

Every universal adapter I find that has 7.5 as an option, seems to have a
current rating of either below, or above the 1500mA I need. They are usually
either about 1000mA, or 1700mA etc.

Does anyone know if this is a required rating, or if it will automatically
only take the current required, as long as it's set to 7.5V ?

For example, if I get the one with only 1000mA rating, will it not work? If
I get the 1700mA one, will it be too much and blow the wireless access
point?

Thanks for any help,
Daniel

Floyd L. Davidson wrote:

Robert Baer wrote:

A supply could be rated at 1000A and work no differntly than
one rated at 1700mA.
It is the *voltage* rating that one must be cautious about.


Almost, but not quite. If a DC supply is significantly under loaded,
the voltage will rise.

That's true if it's unregulated but the voltage change with a regulated
supply is negligible.

How much depends greatly on the design chosen.

For that reason it is probably not a good idea to use a supply
rated significantly higher than the original supply was rated
for... *if* the voltage actually makes any difference at all.

(But if, as is true with many wifi units, the onboard supply is
actually a switching power supply, which is basically
insensitive to input voltage, it simply won't make any
difference at all.)


Now, if there was a way you could measure the actual current
drawn by the unit, i would expect that it would draw less than
1500mA - perhaps as low or lower than 1000mA.

If that were true, then you could use the less expensive supply.


Bad idea. The supply has to be able to provide current at
*peak* usage. Trying to measure that can be very difficult, if
not impossible for most people. With a wireless radio, for example,
the peaks happen when the unit is transmitting and may be for very
short bursts. If you simply measure the current while the unit
is idle, what you measure is a totally misleading value.


However, in your case, it is wiser to use a supply rated at
or more than 1500mA.


Ah, you got that one pegged.