Battery powered DS help

[lcoreyl]

Originally Posted by Alan Anderson

I'm curious to know what failure you believe a fuse would prevent.

excess current

[Alan Anderson]

Originally Posted by lcoreyl

excess current

Excess current is not a failure. It is the result of a failure.

It is also the cause of additional failures, most notably burned wires, and it is those secondary failures which a fuse protects against. But the original fault which led to too much current in the first place won't be affected one way or the other by the presence of a fuse.

[lcoreyl]

Originally Posted by Alan Anderson

Excess current is not a failure. It is the result of a failure.

It is also the cause of additional failures, most notably burned wires, and it is those secondary failures which a fuse protects against. But the original fault which led to too much current in the first place won't be affected one way or the other by the presence of a fuse.

Both routers had the symptom of plug it in and nothing happens and I've ruled out polarity as the problem both times and >12V the second time. at this point linksys has accepted router 1 under warranty, so I have no plans of opening router 2 to inspect. The only other thing I can think of is a difference in impedance from power supplies. Worst case a few ohms difference, in which case the router is designed to handle that change in current, but that's my only theory at this point. That is what leads me to fuses. This will also protect against someone using the rig with battery power >12 V in the future. true, I won't be able know for sure what the actual failure is, but at least I won't have to worry about $160 secondary failures.

So, unless anyone can tell me what we're doing wrong, I'm going to be using fuses, and I stand by my suggestion that others do the same.

[m3rc1l3ss]

I am looking for mobility, so I was looking more towards using 2 of the 7.2 backup batteries from past years, but I cant find the amp hour rating them. Does anyone have any idea what it might be?

After looking around I think I will do a LM317T circuit on the batteries, but I would hate to buy all of the stuff and then find that it lasts for 10 minutes or something.

[J-Mech]

Originally Posted by Alan Anderson

Excess current is not a failure. It is the result of a failure.

It is also the cause of additional failures, most notably burned wires, and it is those secondary failures which a fuse protects against. But the original fault which led to too much current in the first place won't be affected one way or the other by the presence of a fuse.

Well the fuse would protect against a device failure. So it would make a difference by protecting the router.
http://en.wikipedia.org/wiki/Fuse_(electrical)

[Vikesrock]

Originally Posted by J-Mech

Well the fuse would protect against a device failure. So it would make a difference by protecting the router.
http://en.wikipedia.org/wiki/Fuse_(electrical)

To draw enough current to blow a fuse there would already have to be some sort of failure in the router. While a fuse may prevent further failures from occurring, the router does not have any components that are user serviceable for most teams so the extent of the failure is not really relevant. Fuses are meant to prevent further failures and fires, they do not prevent the initial failure.

Also, odds are that there are one or more fuses already contained in the router to prevent a fire in the case of a failure resulting in over-current.

EDIT: The link you posted actually does a pretty good job of describing what a fuse does and doesn't do.

[Al Skierkiewicz]

I believe the original IFI backup battery was 700 maHr but many teams purchased packs that had greater capacity. 1400 maHr seemed to be the norm.

The router unlikely had an electrical failure. Have you tried using the "return to factory default" procedure to load the original settings? Wall wart power supplies are rarely regulated, so electronics already have internal regulators. The WRT610N requires 1.5 amps at the power input.

Tom, I think your description is that you were using a battery from a cell phone to power the router. Or were you using a cell phone charger/ power supply to power the router. In any case, a failure to provide 1.5 amps at 12 volts nominal might have caused the router to corrupt it's firmware settings making it appear dead. The factory restore procedure or a reload of firmware may bring it back to life.

[Tom Line]

Alan, it was our sacrificial switch that died - we never killed the router. For whatever reason, we found it VERY difficult to find a switch at ratshack or officedepot that ran off 12 volts - they all seem to run off 6V.

Again - this was something done in desperation when we realized that if our last port died, we were out of the competition. We ran out the morning of to find the components. After realizing we couldn't find a switch that ran at 12V, we ran back out and got a cellphone car charger that provided .7 amps at 6 volts. We wired that into one of the 12 volt batteries to provide 6 volt power for the switch.

The car charger died, and the switch died at the same time. I can only assume the switch pulled too much amperage, fried the charger, then fried itself. It will no longer power up, so I would guess we killed the voltage regulator, though I never bothered to check.

[Al Skierkiewicz]

Tom,
It is hard to know what the output of a battery charger could be. The 0.7 amp rating could be a "peak" rating based on a pulsed output. Since the switch does not present the same load as a battery would, the charger may have put out a really strange waveform. There are a few protection devices that could be in series with the power input on the switch that may have failed, and may be replaceable if a qualified person were to open the device. In most cases, I do not recommend the use of a charger as a power supply. It seems that many devices are designed for the lower voltage with the advent of lower voltage requirements for microprocessors. 3.3 volt interface electronics are becoming common as well, hence the move to 6 volt power inputs.

[Alan Anderson]

Originally Posted by J-Mech

Well the fuse would protect against a device failure. So it would make a difference by protecting the router.

No.

Fuses do not protect devices. They protect wires from a device failure. Note that the only way to blow a fuse is to draw too much current. The only way for the router to draw too much current is for it to fail. A fuse cannot protect the router from itself.

A fuse might protect against the application of too high a voltage, but only if the device's power input was designed to survive overvoltage and to draw lots of current in the process.