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Old Feb 22, 2012, 01:52 AM
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how to determine polarity of balance charger coaxial/barrel connector?

Hi there- I have 3 different brands of balance chargers- looking at the DC Supply AC Power Adapter packs (which I already have for each of the 3 different brands, for charging out of my electricity outlet at home)- I note that 2 of my brands of balance chargers have a positive center pin, yet 1 has a negative center pin- in an attempt to avoid confusing the DC supply packs- I have labelled which DC supply goes with which balance charger- however my local airfield has 12V battery charging stations and I use the crocodile clips connectors to power my balance chargers at the field to charge my lipos- my challenge is- I haven't labelled the crocodile clip connectors (with a barrel/coaxial connector on the other end)- and they all look the same- I don't want to risk putting the one with a negative center pin into the balance charger that requires a positive center in, or vice versa- is there a way I can test somehow to confirm what the polarity is of the center pin? (just so we're 'on the same page', I have attached a picture of the cable/s in question)- thanks so much in advance for any suggestions! (i have a multi meter if that could be of any use)
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Old Feb 22, 2012, 03:25 AM
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You can use the multimeter to determine which alligator clip corresponds to the center pin. Set the meter to read resistance and then probe the center pin of the barrel connector and each of its corresponding clips. The clip that provides a zero resistance is connected to the center pin. Normally, a red clip will be attached to a battery's "+" terminal and the black one to "-".
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Old Feb 22, 2012, 07:12 AM
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I would also paint the black connector with the neg. centre pin red, just to differ it from the others.

Gord.
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Old Feb 22, 2012, 10:20 AM
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In this country we use allegator clips, not crocodile clips.
(first time I have heard it called a crocodile clip)

Rick
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Old Feb 22, 2012, 12:00 PM
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Up here we call them Beaver clips Just kidding.!!

Gord.
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Old Feb 22, 2012, 12:37 PM
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thanks everyone- I'm a Brit living in the US- hence the old 'croc' terminology-
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Old Feb 22, 2012, 12:40 PM
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Originally Posted by rampman View Post
In this country we use allegator clips, not crocodile clips.
(first time I have heard it called a crocodile clip)

Rick
Out here they call them roach clips
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Old Feb 22, 2012, 12:54 PM
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whitecrest- is there a way to determine the polarity of the barrel connector SOCKET in the charger itself? (I now have conflicting opinions from the hobbyking forums as to what the polarity should be on my turnigy accucel charger and now need to find out what the actual polarity of the charger itself is now..thank you
Quote:
Originally Posted by whitecrest View Post
You can use the multimeter to determine which alligator clip corresponds to the center pin. Set the meter to read resistance and then probe the center pin of the barrel connector and each of its corresponding clips. The clip that provides a zero resistance is connected to the center pin. Normally, a red clip will be attached to a battery's "+" terminal and the black one to "-".
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Old Feb 22, 2012, 01:22 PM
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Originally Posted by whitecrest View Post
You can use the multimeter to determine which alligator clip corresponds to the center pin. Set the meter to read resistance and then probe the center pin of the barrel connector and each of its corresponding clips. The clip that provides a zero resistance is connected to the center pin. Normally, a red clip will be attached to a battery's "+" terminal and the black one to "-".
so I understand you correctly- I'm setting the multimeter to resistance (200 Ohms- lowest setting)- I connect the red probe of the multimeter to the red alligator clip and probe inside the barrel connector with the multimeter's black probe- if this shows no resistance- does this mean the black or the red alligator clip is connected to the center pin or vice versa? (PS- when no resistance is showing- nothing changes on the digital readout- when anything shows- it is only a reading of 0.02 on the 200 Ohm setting- ie. very low- is that enough to say it has resistance compared to nothing showing at all?)- also there is no pin on the barrel connector- the connector is 'female'- the male socket on the charger has the pin

thanks for clarifying
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Old Feb 22, 2012, 06:12 PM
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With the meter set to read resistance, you should get a zero (or very, very low reading) when you simply touch the two probes together. In this case, the meter is being used to test for continuity.

You can identify which clip is attached to the center (pin or socket) of the barrel connector by probing the center of the connector and each clip in turn. When the resistance suddenly drops to zero or just barely above, you've found the clip that is connected to the center.

The color of the clip (there was a red and black one in your photo) that is connected to center should also indicate the polarity of the center because red should always be connected to the battery's positive terminal and black to negative. The red/black protocol is a fairly common convention used in the industry.

On the multimeter, if you connect the black probe to common and the red probe to the voltage socket, you should read correct polarity when the meter is set to read voltage.
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Old Feb 22, 2012, 10:03 PM
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Quote:
Originally Posted by whitecrest View Post
With the meter set to read resistance, you should get a zero (or very, very low reading) when you simply touch the two probes together. In this case, the meter is being used to test for continuity.

You can identify which clip is attached to the center (pin or socket) of the barrel connector by probing the center of the connector and each clip in turn. When the resistance suddenly drops to zero or just barely above, you've found the clip that is connected to the center.

The color of the clip (there was a red and black one in your photo) that is connected to center should also indicate the polarity of the center because red should always be connected to the battery's positive terminal and black to negative. The red/black protocol is a fairly common convention used in the industry.

On the multimeter, if you connect the black probe to common and the red probe to the voltage socket, you should read correct polarity when the meter is set to read voltage.
Hi whitecrest- thank you so much again for your support- it is greatly appreciated-

I have attached a couple of pictures to illustrate what I think you are suggesting I do- image # 206 on the left shows one probe in the barrel connector and the other probe connected to the black alligator clip- even though the reading has what looks like a '1' showing- I believe the multimeter is showing no resistance in this instance as the '1' is there even when not connected to anything in this setting on the multimeter- when I connect the probe to the red alligator clip (picture # 207 on the right)- a little resistance is shown- though a figure around 50 comes up on initial contact for a split second- it settles within a couple of seconds on a figure on the readout of 0.02 on the '200 Ohms' setting ie. 4 Ohms- even though this is negligible-- is this enough to prove that the the red alligator clip has resistance and therefore black alligator clip is connected to the inside center of the barrel and therefore requires a negatively charged center pin? If I am following your instructions correctly- my next confusion is that all three of my alligator to barrel connector cables produce the same results, suggesting all three of them have a negatively charged center, which wouldn't make sense (as stated in my first post- two of my chargers require positively charged center pins (looking at the info on their corresponding DC Supply AC Power Adapter packs) and only one requires a negatively charged center pin..yet each of these (alligator clips to barrel connector) cables came with each of the balance chargers)- am I mistaken in thinking it actually matters what the polarity of center pin in the barrel connector (on the alligator clips to barrel connector cables) actually is? - I'm sure it does matter..

the third picture on the far right is just testing the resistance as suggested by connecting the red and black probes of the multi meter together- the figure on the readout was continually changing..

thanks again or anyone's feedback- can't wait to clear up the confusion and label these cables accordingly asap
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Old Feb 22, 2012, 10:35 PM
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If you read the manual of your meter, you will find that that a "1" on leftmost digit means "out of range" or "infinity", ie. an open connection. Also, the reading "0.02" is not a multiplier to the selected range, it simply means an absolute value of 0.02 ohms, ie. a solid connection. Random readings for a short time before the reading settles are normal and should be ignored.

Your first picture shows that the black clip is not connected to the center barrel.

The second picture shows that the red clip is connected to the center barrel.

The third picture shows an imperfect contact between probes. Maybe they are dirty, not firmly held to each other, maybe test leads are damaged (connection between actual probe tip and wire frayed etc.), a poor contact on meter side connectors, faulty meter... The possibilities are endless.
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Old Feb 23, 2012, 12:28 AM
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Originally Posted by jkettu View Post
If you read the manual of your meter, you will find that that a "1" on leftmost digit means "out of range" or "infinity", ie. an open connection. Also, the reading "0.02" is not a multiplier to the selected range, it simply means an absolute value of 0.02 ohms, ie. a solid connection. Random readings for a short time before the reading settles are normal and should be ignored.

Your first picture shows that the black clip is not connected to the center barrel.

The second picture shows that the red clip is connected to the center barrel.

The third picture shows an imperfect contact between probes. Maybe they are dirty, not firmly held to each other, maybe test leads are damaged (connection between actual probe tip and wire frayed etc.), a poor contact on meter side connectors, faulty meter... The possibilities are endless.
Hi- thanks for your reply

This is a brand new multi meter and therefore it's unlikely the contacts are dirty or damaged- it is also my first multi meter and have never used one before and it didn't come with a manual/instructions

regarding the first picture (with the multi meter's red probe inserted and making contact inside the barrel connector and the black probe connected to the black alligator clip)- no matter what I do to try and make a supposed better connection (and the components do seem to be making a good enough connection)- the readout remains the same with the '1' displayed..if no resistance is showing what should display on the readout - a '1' as displayed or should it read '0' Ohms or something else?

can you clarify if the 2nd picture with a solid connection, even if only a negligible figure of 0.02 Ohms- never the less- as according to whitecrest's notes is still the one with resistance? - meaning the other has no resistance- therefore meaning the center pin is negative or not?

How can you tell the third picture shows an imperfect contact between the probes?

Thank you
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Old Feb 23, 2012, 08:40 AM
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Originally Posted by TheSelf View Post
regarding the first picture (with the multi meter's red probe inserted and making contact inside the barrel connector and the black probe connected to the black alligator clip)- no matter what I do to try and make a supposed better connection (and the components do seem to be making a good enough connection)- the readout remains the same with the '1' displayed..if no resistance is showing what should display on the readout - a '1' as displayed or should it read '0' Ohms or something else?
First, the colors of meter leads do not matter in this measurement. The black clip of your charger cord is not connected to the center barrel of the coaxial connector. The resistance from black clip to center barrel is infinitely large (or at least greater than 20 gazillion ohms). Your meter is correctly showing that the resistance is greater than what it can measure. There is nothing you can or should do about it.


Quote:
can you clarify if the 2nd picture with a solid connection, even if only a negligible figure of 0.02 Ohms
It is the resistance of the clip, wire, connector and solder joints between them. It is as good as you will ever get. To get zero ohms, you would need supraconductive materials cooled within a fraction of a kelvin from absolute zero.


Quote:
...according to whitecrest's notes is still the one with resistance? - meaning the other has no resistance- therefore meaning the center pin is negative or not?
I'm afraid I don't understand what you are trying to say here. If you mean that there is no resistance between black clip and center barrel, you would be wrong. There is resistance, in fact more resistance than your meter is capable of measuring. The black clip is not connected to the center barrel. The red clip is connected to the center barrel. If you connect the red clip to the positive terminal of a power source, the center barrel will be positive. If you connect the red clip to the negative terminal of a power source, the center barrel will be negative.


Quote:
How can you tell the third picture shows an imperfect contact between the probes?
The meter is not showing zero ohms.


As an exersise, assume that the black clip is connected to the outer shell of the coaxial connector. First answer these questions: What will the meter show if you connect the probes to the black clip and outer shell of the connector? What will the meter show if you connect the probes between red clip and outer shell? Only after having answered these questions, verify the answers by making actual measurements.
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Old Feb 23, 2012, 09:28 PM
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Originally Posted by jkettu View Post
First, the colors of meter leads do not matter in this measurement. The black clip of your charger cord is not connected to the center barrel of the coaxial connector. The resistance from black clip to center barrel is infinitely large (or at least greater than 20 gazillion ohms). Your meter is correctly showing that the resistance is greater than what it can measure. There is nothing you can or should do about it.


It is the resistance of the clip, wire, connector and solder joints between them. It is as good as you will ever get. To get zero ohms, you would need supraconductive materials cooled within a fraction of a kelvin from absolute zero.


I'm afraid I don't understand what you are trying to say here. If you mean that there is no resistance between black clip and center barrel, you would be wrong. There is resistance, in fact more resistance than your meter is capable of measuring. The black clip is not connected to the center barrel. The red clip is connected to the center barrel. If you connect the red clip to the positive terminal of a power source, the center barrel will be positive. If you connect the red clip to the negative terminal of a power source, the center barrel will be negative.


The meter is not showing zero ohms.


As an exersise, assume that the black clip is connected to the outer shell of the coaxial connector. First answer these questions: What will the meter show if you connect the probes to the black clip and outer shell of the connector? What will the meter show if you connect the probes between red clip and outer shell? Only after having answered these questions, verify the answers by making actual measurements.
Hi - thank you for your support and patience - it has been greatly appreciated!

It seems I confused the readouts on the multi meter and got them the wrong way round (thinking the 0.02 Ohms equaled 'resistance' and the '1' meant no resistance (as the readout didn't change), when in fact it actually is vice versa and so in fact the center pin is positive- thanks for clearing that up

with gratitude,

Justin
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