Non-bike related electrical question.

[StudEbiker]

I ordered a hair trimmer from DX knowing that it had a 220 plug on the wall wart but planning to find a 110v wall wart with the same output voltage and putting it on the end of the charge cord. My question is how close do I need to be? The 220v plug has an output of 3v 80ma. I have a spare 110v around that is 4.5v 100ma. Would this one work or do I need to get the voltage down closer to 3?

 

[StudEbiker]

I ordered a hair trimmer from DX knowing that it had a 220 plug on the wall wart but planning to find a 110v wall wart with the same output voltage and putting it on the end of the charge cord. My question is how close do I need to be? The 220v plug has an output of 3v 80ma. I have a spare 110v around that is 4.5v 100ma. Would this one work or do I need to get the voltage down closer to 3? Would there be some kind of BMS circuit to prevent the batteries from overcharging?

 

[yopappamon]

Get a multi voltage (universal) power adapter. I have one, it has a switch for voltages from 3 to 12v, all the different tips that you can reverse the center pin + to -

http://www.amazon.com/PowerLine-90304-Variable-Universal-Compatability/dp/B0042X8XOG

 

[StudEbiker]

I'd rather not spend the coin right now. That adapter is the same price I paid for the trimmer.

 

[fizzit]

With 4.5v you will be running approximately 2.25 times the power of that at 3v (if it obey's ohm's law) so it might fry. Personally, if it draws only 80ma, I would just hook up two AA batteries in series to get 3v.

 

[StudEbiker]

Sorry if I wasn't clear. The wall wart connector is for charging internal batteries. It is a cordless device that needs to be charged by the power supplied by the wall wart.

 

[StudEbiker]

oops, it looks like I did a double post on this. I hit the stop button after hitting submit to edit the post further, but it looks like it went through before I hit the stop button. Sorry about that.

 

[amberwolf]

I merged them for you; I can delete the duplicate OP if you like, too.

Regarding using the 4.5V adapter, you could install two diodes out of an old PC PSU's AC-input section in series to the + line on the wallwart's output. THat'd take it down about 1.4V, making it close enough to the original adapter's voltage to probably work normally. The 100mA vs 80mA capability is probably fine, in that the internal charger in the trimmer will likely only pull <80mA regardless of what the adapter is capable of.

The only potential issue I can think of is that the trimmer may not put enough of a load on the new adapter, and so it's voltage may be higher than expected, if it is the old transformer-diodes-capacitor type, rather than a switching type. The former is usually notably heavier than the latter, so tends to be easy to tell them apart.

You coudl test beforehand by using a resistor across the new adapter's output to present the same load the trimmer will. Add the series diodes first, then the resistor will need to be R = E / I, (ohms = V / A). So 3.6 / 0.08, or 45 ohm. Paralleling four 180 ohm resistors would be perfect. Two 100 ohm resistors will be very close if you have no 180s. The resistors might be found within the PC PSU, too.

Once the resistors are across it, clip or hold your DC Volt meter probes on the resistor leads, then plug in the adapter. It should read 3.6V, if it does not and reads significantly higher, you'll need to add a bit more load to it. Once you find the right load to make it read 3.6V, you could then leave just that load on there, then remove the 45ohm load, and hook it up to the trimmer. Verify voltage again, and if it's ok, you're all set.

 

[torker]

Will your Lifepo charger do 1s ? If so maybe you can use it

 

[StudEbiker]

Will your Lifepo charger do 1s ? If so maybe you can use it

I guess I could set the Lyen DC-DC converter that is on the bike to 3v and put some andersons on the clipper charge wire and charge it off the bike's battery. Oddly enough, that is almost sounding like the easiest solution.

AW- please feel free to delete the first post and thank you for the merge.

 

[Roy Von Rogers]

Try this.......
http://cgi.ebay.com/AC-100V-240V-Converter-Adapter-DC-3V-1A-Power-Supply-US-/320655701914?pt=LH_DefaultDomain_0&hash=item4aa891b79a

Also, and you may know that, what type of a wallwart is this, does it have a transformer, is it heavy ??
Some switched units have a wide input power and can handle 120v US power, all you wouuld need to do is get a cheap plug converter.

Roy

 

[StudEbiker]

That Ebay converter would be perfect...too bad it's in HK. :? I'll check to see if there's one a little closer.

 

[StudEbiker]

Well, it isn't very pretty , but it works.

 

[Alan B]

Suicide cord.

Should always plug those into a GFCI outlet.

 

[StudEbiker]

Will do. Thanks!

 

[amberwolf]

Also, looks like with the size of the pins on the back of the wallwart, you could stick those andersons right onto it. Maybe a tad less unsafe.

Personally, I'd just solder the suicide cord right to the wallwart pins, then heatshrink it up for safety (or at least a few layers of electrical tape over some plastic tubing covering the exposed metal).

 

[StudEbiker]

I was worried about the heat from the solder ruining something inside the converter. The alligator clips on the andersons is just one of a few different kinds of things like that I have set with andersons for different uses. I can improve upon it for sure, but I just wanted to see if this would work and it looks like it does. I'll probably just go ahead and order a cheap 220v to 110v adapter online from Hong Kong, but I didn't want to wait that long to use the clipper.

 

[amberwolf]

Just like with soldering cells and FETs and such, as long as you use a big hot iron and solder quickly, there should be no damage even to the plastic casing. You can also clamp on a copper or aluminum bar to the pins right at the case, to help sink heat away there but allow it to heat the tips where you're adding the cord wires. Might have to file off a bit of the shiny silver coating on teh pins first, as it might not be easily tinnable (but usually there's brass inside that, if not it's steel and that's probably not gonna solder).


I use alligators across bigger andersons (an SB-50 on the WattsUp WU1) to the IEC output of the Vpower charger, until I can free up another SB50 to stick on the Vpower. Perfectly safe as long as the dogs don't mess with it, but they have, sometimes, so I ended up with duct tape (saved off the Vpower pack itself :lol over the thing to keep them from bumping them loose and blowing things up.


If it works like it does, just put a short little cord on the prongs and use it as-is. Why spend money you don't have to?

Plus, if you look around at Goodwill and other thrift stores or yard sales, I can virtually guarantee you that you will run across a little adapter from that unit's two-prong style to the USA two prong 110V style, allowing you to use it without modification. I know that I have at least one around here someplace, if I can find it, originally from a box of assorted electrical stuff for a buck at a yard sale. It's like the size of two celphone batteries stacked on each other, if that. Including the prongs. Like this:

 

[dnmun]

how can you plug a 240V power supply into a 120V GFCI plug. i hate those things, i avoid using them because they cost so much for no useful reason. how many people get electrocuted that way? just more stupid rules for the code book imo.

maybe your 240 power supply will run off the 120V standard AC though.

 

[Alan B]

Quite a few people each year die from 120V electrical shocks. It only takes about 15 milliamps to stop the heart. The GFCI trips if more than about 8 milliamps of current goes "missing" (subtracts hot from neutral current in real time) indicating there is a problem. Amazing protection technology for ten bucks, actually.

Most modern small power supplies can operate from a wide range of voltage and frequency, such as 100-250 VAC 50/60 hz. So all that is needed is an adapter to fit the pins, no electrical transformation is required.

 

[Alan B]

GFCI outlets are generally required near water such as kitcens and bathrooms, and outside outlets. Dry skin generally does not conduct enough current to be dangerous at 120VAC, but when wet it can easily be fatal.

 

[amberwolf]

how can you plug a 240V power supply into a 120V GFCI plug.

Most of the little wallwarts I've seen, even those with the 220 plug like that, say right on them something like "Input 100-220VAC 50-60Hz", and a very few I've seen (but don't have) come as a 220 plug like that with the USA 110V adapter already on it, so you wouldn't even think about it when using it (except that it sticks out from the wall further than normal).

It doesn't give a ground prong, though, so if that's required for the GFCI to operate, it doesnt' help with that situation.

 

[dnmun]

the output on the switch mode power supplies are totally isolated from the input.

 

[Alan B]

GFCI's don't require ground to operate. In fact as I understand it the code allows installing only a GFCI type outlet if there is no ground available in certain situations as there is no way to safely install a grounded outlet. In this installation case the safety ground of the GFCI is not grounded. (I'm not a code expert but I work with some).

The GFCI works by subtracting hot current from neutral current and tripping if the result is not zero. Ground current is not monitored. The fault exists when current from the hot does not return on the neutral which happens when another unwanted path is presented by a failure. That current might or might not return on the safety ground.

I recommended GFCI in this case since a suicide cord was in use and the AC prongs were exposed.

A properly insulated wall wart does provide protection. However they are sold for a few dollars and made in large quantities in factories with little quality control, and failures can happen.

We had some special hand-assembled "safety rated" relays fail in a very unsafe way due to errors in the assembly process. The insulation was partially damaged and over time the wires shorted. So while they passed rigorous initial testing they later failed in a way that they were never supposed to fail. Failures can happen even in "good stuff". In this case the failure was tracked to moving manufacturing offshore and improper training and assembly procedures.