Can I splice a DC power cord?

[Phil Mueller]

I hate to be an admin edit, but has your doctor even approved you using that thing...or are you just going to shorten the cord and stare at it.

[Mike Henderson]

This is a no-brainer: cut, splice, move on. I always throw in a ferrite bead when dealing with DC - AC alternates between the positive and negative providing a 'wave' of energy. DC is a straight-line voltage (why its so much more dangerous than AC) - I include the ferrite to preserve that straight line... a little overkill but the bead is a couple of pennies = well worth it. Also, completely not necessary but solder and shrink tubing is the way to fly.

A ferrite on the line is generally used to block high frequencies from being fed back into the power system. See here. Ferrites are often used when you have a switching power supply to block the switching frequency from the power system. Also to meet FCC Part 15 requirements.

I don't know what purpose a ferrite would have on a DC line, unless the DC line contained a lot of high frequency ripple.

Also, I don't know if there is a real difference between DC and AC as far as danger is concerned but early in power systems history there was the "War of Currents" where Edison tried to prove that AC was more dangerous than DC. The only thing I can think of is that the peak voltage of an AC circuit is higher than the RMS voltage, and higher than the DC voltage.

Mike

[Kent A Bathurst]

I hate to be an admin edit, but has your doctor even approved you using that thing...or are you just going to shorten the cord and stare at it.

Very good, Phil. Very good, indeed. In fact - darn near perfect. I literally howled out loud when I read that.

You even phrased it in the "vernacular du jour". I knew it would catch on.

I have the next surgeon's appt Wed 26 Aug. I will do nothing before that. However, he told me 5.5 weeks ago that I was clear to do "normal day-to-day activities" so I have been washing the dishes [which is my part of the program with my gourmet cook wife]. That includes wiping the kitchen counters down. WHich is not much different than running the ROS - especially at its ~~2# weight, which was a big attraction. And - no real weight once on target.

My money [literally] is on being cleared for take off.

I also need from him: 5# resistance/weight for a pushing motion from hip to extension, which clears jointer, TS, BS and handsaws, and also need - stretch goal - 15# pull down motion, which clears the mortiser, DP, and CMS.......I'm not going to bring up the hammer for chisels....If I get the others, then that must be good, right?

So - Yes, I am staring at it, for the moment. I got stymied - need 3" of 18 ga solid-conductor insulated copper wire for 2 internal jumpers to turn the 2-conductor wire into what the 4-pole connector needs. Which my neighborhood Ace does not have. But Azon prime does. Plus 24' 9" extra, for a very small price [compared to the Ceros], delivered on Tuesday.

Thanks. A lot. You are very clever, Phil. I'm going to keep my eye on you..........

Are you a U of M grad? I might have to put you on the "pass" list with Turk.

[Kent A Bathurst]

A ferrite on the line is generally used to block high frequencies from being fed back into the power system. See here. Ferrites are often used when you have a switching power supply to block the switching frequency from the power system. Also to meet FCC Part 15 requirements.

I don't know what purpose a ferrite would have on a DC line, unless the DC line contained a lot of high frequency ripple.

Also, I don't know if there is a real difference between DC and AC as far as danger is concerned but early in power systems history there was the "War of Currents" where Edison tried to prove that AC was more dangerous than DC. The only thing I can think of is that the peak voltage of an AC circuit is higher than the RMS voltage, and higher than the DC voltage.

Mike

I am pretty comfortable that neither the AC from the wall to the transformer nor the DC from the transformer to the ROS are going to kill me.

[Edward Oleen]

AS LONG AS YOU GET THE POLARITY CORRECT!!!!!!!!! Unlike ac, if the tool is DC operated there IS a positive lead and a negative lead, AND IT DOES MAKE A DIFFERENCE!!!! UNLIKE AC.

Well, it does make a difference in AC too, at least 117v ac, as opposed to 220 ac (3 wire or 4 wire)...

If you don't understand what I'm talking about, go find an electrician. At the least, if you reverse wire your tool you could either have it running backwards. On the other hand, you might burn it out. An expensive mistake...

[Kent A Bathurst]

I'm cool with that. I have an unmolested example [an OEM extension cord] to use as a reference.
Very good grooming tip, Edward. Thanks.

OT: You a fan of TDY?

[John Kananis]

It takes more DC (current) than AC to kill you.

Hello Phil: I believe that there is a bit of confusion on this subject. Current (the amperage being drawn) is independent of voltage (each being only 1/3 of the equation).

Lets assume two signals, one a sinusoidal (AC) running at 120 volts and drawing 10 amps and the other a DC signal running at 60 volts and 10 amps. The AC signal is running at 1200 watts and the DC signal is only at 600 watts. In this example both signals have an extremely high potential of fatality (the current necessary to cause death is in the miliamp range - especially if you're grounded with two appendages in contact with the circuit) but the 'weaker' DC signal is a higher potential for that mark.

As the AC signal moves from positive to negative, your muscles contract and relax giving you an opportunity (sometimes) to release your hold and end the shock before a fatality can occur (a bit of an extreme, but think of static electricity shocks on those cold dry days; depending on the degree of charge you could be zapped with up to 40,000 volts but since its instantaneous, it doesn't harm you). Unless you've grabbed a hold of a negative rail (not usually the case) the DC signal is in constant positive voltage (constricting your grip and thus 'holding' you to the circuit).

I hope this was useful/helpful.

[John Kananis]

A ferrite on the line is generally used to block high frequencies from being fed back into the power system. See here. Ferrites are often used when you have a switching power supply to block the switching frequency from the power system. Also to meet FCC Part 15 requirements.

I don't know what purpose a ferrite would have on a DC line, unless the DC line contained a lot of high frequency ripple.

Also, I don't know if there is a real difference between DC and AC as far as danger is concerned but early in power systems history there was the "War of Currents" where Edison tried to prove that AC was more dangerous than DC. The only thing I can think of is that the peak voltage of an AC circuit is higher than the RMS voltage, and higher than the DC voltage.

Mike

Ya, like I said overkill but doesn't hurt - anything is possible once you interrupt a circuit and introduce a new connection (as in shortening a power line), no? You seem quite knowledgeable, in the industry (I am not)?

Oh, and yea Edison was a douche about that whole smear campaign. He had lots and lots invested in so many DC patents.

[Phil Mueller]

Are you a U of M grad? I might have to put you on the "pass" list with Turk.[/QUOTE]

i am not, but daughter is. She was in the marching band, so our desire for a winning season was motivated by getting her to a good bowl game...as it turned out, Outback and Sugar. Great fun for the family. Not sure that qualifies for a pass.

[Ken Krawford]

Not to be a wet blanket here but I'd be willing to bet that your surgery on the cord would technically void your warranty. Just sayin'.

[Myk Rian]

Holy Moly. 24 replies to figure it out.

[Pat Barry]

Hello Phil: I believe that there is a bit of confusion on this subject. Current (the amperage being drawn) is independent of voltage (each being only 1/3 of the equation).

Lets assume two signals, one a sinusoidal (AC) running at 120 volts and drawing 10 amps and the other a DC signal running at 60 volts and 10 amps. The AC signal is running at 1200 watts and the DC signal is only at 600 watts. In this example both signals have an extremely high potential of fatality (the current necessary to cause death is in the miliamp range - especially if you're grounded with two appendages in contact with the circuit) but the 'weaker' DC signal is a higher potential for that mark.

As the AC signal moves from positive to negative, your muscles contract and relax giving you an opportunity (sometimes) to release your hold and end the shock before a fatality can occur (a bit of an extreme, but think of static electricity shocks on those cold dry days; depending on the degree of charge you could be zapped with up to 40,000 volts but since its instantaneous, it doesn't harm you). Unless you've grabbed a hold of a negative rail (not usually the case) the DC signal is in constant positive voltage (constricting your grip and thus 'holding' you to the circuit).

I hope this was useful/helpful.

I don't think this is helpful at all. In reality,its mostly incorrect information. Maybe just too dumbed down for the masses. a) its the current THROUGH your body that is important, not the amount of current flowing through the circuit. b) the AC frequency of 60Hz is much faster than anything your body can physically respond to - you can't just let go - in fact, its more likely than not that you will not be able to let go of an AC line that is conducting current through your body if you have actually grasped one or both ends without outside help of sorts. c) static electricity is completely different animal than AC or DC power - there is no reason to even mention them separately (except to point out they are not the same).

Oh yeah, Kent, please make sure you DISCONNECT the circuit from its power source BEFORE you start cutting and splicing. I'm sure that much everyone actually knows.

[Phil Thien]

Hello Phil: I believe that there is a bit of confusion on this subject. Current (the amperage being drawn) is independent of voltage (each being only 1/3 of the equation).

(Sources: http://www.quora.com/Which-one-is-mo...nt-and-voltage)

Note that I'm only posting this because this is fairly important. I know (hope) we all treat any sort of potential with respect, but...

Having said that, I would rate AC as more dangerous owing to the following reasons,

1. To produce the same excitatory effects, the magnitude of DC flow of constant strength shall be two to four times greater than that of the AC. i.e more DC current is required to induce the same harmful effects as AC current.

Why? The main difference between the effects of AC and DC on the human body result from the fact that excitatory actions of the current are linked to the changes of the current magnitude especially when making and breaking the current. Excitatory actions of the current include stimulation of nerves and muscles, induction of cardiac atrial or ventricular fibrillation. To produce the same excitatory effects, the magnitude of DC flow of constant strength shall be two to four times greater than that of the AC.

2. Accidents with DC are much less frequent than would be expected from the number of DC applications, and fatal accidents occur only under very unfavorable conditions, for example in mines. This fact is highlighted in the IEC publication 60479 - Effects of current on human beings and livestock. This reveals that DC is only an 'occasional culprit' compared to the 'serial killer' AC.

3. Ventricular Fibrillation is considered to be the main cause of death by electric shock. The probability of a human suffering from Ventricular Fibrillation is much higher in the case of AC than DC.

Why? For shock durations longer than the cardiac cycle, the threshold of ventricular fibrillation for DC is several times higher than for AC. For shock durations shorter than 200 milli seconds, the threshold of fibrillation is approximately the same as for AC measured in RMS values.

4. The total impedance of the human body is higher for DC and decreases when the frequency increases. Since the impedance for DC is higher, the severity of electric shock would be comparatively lesser than AC.

Why? The impedance of the human body is one of the factors influencing the effect of electrical current on humans. The total impedance of the human body depends upon a number of factors (including the frequency of electrical supply). Therefore, the impedance of the human body is higher for DC and decreases when the frequency increases.

5. It's comparatively easier to let go of the gripped 'live' parts in the case of DC than AC. This is in contrary to popular belief.

To quote the popular belief, one such argument is shown below,

"AC would allow your muscles enough time to pull your limb away from the 'live' part because of the alternating cycles (AC frequency) which pass through zero. DC current, on the other hand, has continuous flow due to the absence of frequency oscillations and therefore you can't pull your limb away from the 'live' part.''

I could see many such 'flawed' arguments prevalent on the internet - especially the science forums debating on this topic. But, this is simply a myth.

Why? The "let-go" current is the best experimental measure we have of the effect of electricity on humans. The "let-go" current is the lowest level of current passing through a human subject through an electrode held in the hand that makes the subject unable to open his hand and drop the electrode. As mentioned in the IEC publication 60479 - Effects of current on human beings and livestock, the let-go of parts gripped is less difficult in the case of DC. This is based on experimental evidence.

Given the above reasons, we can safely conclude that AC is more dangerous than DC. Nevertheless, you should always avoid contact with high-voltage electrical conductors, regardless of the type of electrical current.

[Martin Wasner]

Not to be a wet blanket here but I'd be willing to bet that your surgery on the cord would technically void your warranty. Just sayin'.

Considering the less than stellar reliability of the Ceros, probably a good idea. Great sander, good warranty, but they do break on the regular. I've had good luck with both of mine, but the shop next door had one crap out after a few months. I had a salesman tell me the other day he sold twenty to a shop that needed sixteen so they had some spares.