OT: Will These Work?

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On Sun, 27 Sep 2009 21:46:35 +0100, "Calvin Sambrook"

Like an oversize phone charger?
Oh, I don't like them. 8-))
And I don't like the bevy of low quality adapters they come with.
I've seen new routers, not necessarily the latest one, by reputable manufacturers starting at 16 on "one day only" sales.

My current modem - router has mains psu built in. It's predecessors all had wall warts but I think three of them on the trot had overheating problems (as does this one) causing disconnections.
So personally now I don't deviate from the standard setup.
NB of the two VIGOR routers I had one had an AC power supply and the other was DC.
Oh and since I got shot down on one group who accused me of "cooking" my routers I live in a normal modern house maintained at normal temperatures, although the modem - router is, for the moment, unavoidably on a shelf above my desk directly above my LCD monitor.
Derek
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connection if it's an ADSL modem/router combo. 3Com had a major problem a few years ago with a cheap plugtop SMPSU they supplied with one of their ADSL routers.

of the box full of 'useful' bits n bobs under the stairs.

for their internal regulators, if you drop the input voltage the switch has to stay on for longer and thus it dissipates more power, probably not enough to overheat it but...
For a linear regulator the opposite is true, the lower the voltage the less power it has to dissipate.
--
Clint Sharp

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writes

As I had my Silly Scope out for other, much scarier, reasons I took a quick look at the Tesco SMPS running my doorbell. Set to 6V and driving only two LEDs at about 30mA it had about 50mV of essentially unstructured noise. Fastest rise/fall times in the 1nS region so probably no components over 500kHz. I don't know what it takes to upset a router but if any of my guys designed anything which fell over because the incoming power had that sort of noise on it I'd cry.

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On Tue, 29 Sep 2009 22:22:05 +0100, Calvin Sambrook wrote:

An ADSL "router"...
ADSL2 uses carriers from around 25kHz to nearly 1.1MHz, ADSL2+ goes up to 2.2ish MHz. MF broadcast stations can reduce the data rate, interference at night from foreign MF stations knocks a good 512kbps to 1Mbps of my link.
http://www.flickr.com/photos/allsorts-60/3931727826
OK it's only 50mV on the power rail but the bit of wire connecting PSU to router will radiate nicely and ...
--
Cheers
Dave.




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other than a simple LED or resistive load and check again. I'm not saying it's a bad PSU in the grand scheme of things but that it's a little too cheap to be really good.

the PSU was exceptionally bad and you'd probably have problems with anything else you powered from that PSU (perhaps not your doorbell or LEDs though)
ADSL is a fairly special case though, RF interference picked up by the telephone line can cause a modem/router to lose sync, it's not the case that it falls over because of the noise, it's that the ADSL 'signal' gets swamped by the noise, reducing the SNR to a point where it's unusable.
500KHz is almost smack bang in the middle of the band of frequencies ADSL uses so if it's close to the phone line (which is a given because you're powering the router with it) then it could cause problems.
--
Clint Sharp

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writes

Would you care to expound upon that last comment?
--
Woody

harrogate three at ntlworld dot com
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The power dissipated by a linear regulator is the product of the current through it and the differential voltage between input and output.
If the input voltage is lower, for a given output voltage, less power is dissipated by the regulator.
MBQ
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the *input* voltage to the regulator the less power it has to dissipate' but given the context I thought my meaning would be apparent.
F'rinstance, if you have a 5 volt linear regulator passing 1 amp and an input voltage of 10 volts then the regulator will have to dissipate 5 watts, if you have the same regulator but with a 15 volt input then it has to dissipate 10 watts.
Linear regulators dissipate power as heat so feeding one with a lower input voltage will generate less heat.

--
Clint Sharp

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Clint Sharp wrote:

With the proviso that they need a certain amount of head room to work properly. So a 5V regulator will behave as you describe, but an input voltage of less than say 7V may prevent it from working correctly at all.
--
Cheers,

John.

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writes

Exactly where I was going. Most 'normal' (as distinct from low drop-out types) actually require an overhead of 2.3V, plus you have to consider mains variations, so a starting target input of about 8V (possibly even more) is more like it.
--
Woody

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Maplin have a few that should work. The cheapest is 12 http://www.maplin.co.uk/Module.aspx?moduleno "7631

A nice dual band one so the uncongested 5G band can be used would be a good idea IMO.
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dennis@home wrote:

or 6 here:
http://www.solwise.co.uk/psu.htm
--
Cheers,

John.

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What, dropping from 12v to 9V ?

--
geoff

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