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Offline Jak24Topic starter

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wires
« on: May 31, 2010, 11:48:52 AM »
hi

What kind of wires do you suggest i use to connect these motors:
http://shop.maxonmotor.com/ishop/article/article/222049.xml
and this motor
http://shop.maxonmotor.com/ishop/article/article/2516.800-11.111-000.xml
i already have these wires but i don't know if they could handle the current :
http://www.radioshack.com/product/index.jsp?productId=2103801
this is the battery I'm using:
http://www.all-battery.com/12v2600mahnimhbatterypack11620.aspx 7
PS: i want to solder the wires to the motors would this affect the wires in any way ?

thanks

Regards
Jak24

Offline waltr

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Re: wires
« Reply #1 on: May 31, 2010, 01:59:18 PM »
The battery has 18ga wire (hint, hint).
The first motor will draw almost 4Amp on starting and when stalled so 18ga is plenty. But, this is not the complete question.
What size fuze are you going to use? You do want the fuze to blow before the wire melts.
Second consideration is the voltage drop due to the wire resistance and current. How long are the wires?

If you google wire gauge you will find tables showing the max recommends current and the resistance per length of common sizes,
Her's one:http://www.powerstream.com/Wire_Size.htm

Soldering the wire to the motor terminals is recommended for the most secure mechanical and electrical connection.

Offline Jak24Topic starter

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Re: wires
« Reply #2 on: June 01, 2010, 09:46:16 AM »
HI

Thanks for reply
well technically I'm not going to use any fuse.....
but if you recommend it  then i do have 5 - 6 amp fuses.
but if i don't use any fuses the wires I mentioned should work fine... right?
PS : so if battery is 18ga wire, that, or anything better would do fine?
Thanks

Regards

Jak24

Offline tmoney68

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Re: wires
« Reply #3 on: June 01, 2010, 10:37:44 AM »
You should ALWAYS fuse off the battery, very bad things can happen (Not that I have any personal experience)  ::)

Offline Jak24Topic starter

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Re: wires
« Reply #4 on: June 01, 2010, 12:15:07 PM »
OK but .... i mean how could there be a overload or a short, my battery always provides 12v(roughly)?
well if you think i really should use one, I'll put it in .
but back to the point :
the wires I mentioned should work fine... right?:
http://www.radioshack.com/product/index.jsp?productId=2103801
thanks

regards
Jak24

Offline waltr

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Re: wires
« Reply #5 on: June 01, 2010, 02:07:26 PM »
Quote
i mean how could there be a overload or a short, my battery always provides 12v(roughly)?

Murphy's law!
There are just too many ways to create a short or overload. Here's a few I've experienced:
Motor windings overheat and short together.
A component fails and shorts internally, caps, ICs.
A cap or IC is wired or inserted backwards.
Two wires get pinched together, cutting through the insulation and shorting.
Slipping with a screwdriver or other tool and shorting two contacts.
Connecting the wrong wires together.
Miscalculating a resistor value or misreading a resistor value that draws way too much current when the circuit is turned on.

Yes the battery will try to provide 12V but at what current? What happens when the load becomes close to zero Ohms? Hint: use Ohm's Law to calculate I. Then what happens at the battery?

Offline Jak24Topic starter

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Re: wires
« Reply #6 on: June 02, 2010, 07:16:11 AM »
HI
Quote
i mean how could there be a overload or a short, my battery always provides 12v(roughly)?

Murphy's law!
There are just too many ways to create a short or overload. Here's a few I've experienced:
Motor windings overheat and short together.
A component fails and shorts internally, caps, ICs.
A cap or IC is wired or inserted backwards.
Two wires get pinched together, cutting through the insulation and shorting.
Slipping with a screwdriver or other tool and shorting two contacts.
Connecting the wrong wires together.
Miscalculating a resistor value or misreading a resistor value that draws way too much current when the circuit is turned on.

Yes the battery will try to provide 12V but at what current? What happens when the load becomes close to zero Ohms? Hint: use Ohm's Law to calculate I. Then what happens at the battery?

OK so : 12 / .... I'm not sure of the resistance, how do i calculate that? ..... = I
if i use 5-6 amp fuses they should do the job right?

Thanks 

Regards

Jak24

Offline waltr

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Re: wires
« Reply #7 on: June 02, 2010, 11:39:05 AM »
Quote
OK so : 12 / .... I'm not sure of the resistance, how do i calculate that? ..... = I

OHM's LAW, google it.

Anyway, if you tried to calculate the current you would find that with a resistance close to zero (say 0.01 Ohm) the current draw from the battery would go close to infinity (ok, only 1200Amps). This would severely overheat the battery and it could rupture and maybe even catch fire. That is if the wire didn't catch fire and burn off first.

Did you look at the wire table I posted the link to?
Will 18ga wire carry 5-6 amps?


Offline Jak24Topic starter

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Re: wires
« Reply #8 on: June 03, 2010, 08:49:19 AM »
HI

Quote
OK so : 12 / .... I'm not sure of the resistance, how do i calculate that? ..... = I


OHM's LAW, google it.

Anyway, if you tried to calculate the current you would find that with a resistance close to zero (say 0.01 Ohm) the current draw from the battery would go close to infinity (ok, only 1200Amps). This would severely overheat the battery and it could rupture and maybe even catch fire. That is if the wire didn't catch fire and burn off first.

Did you look at the wire table I posted the link to?
Will 18ga wire carry 5-6 amps?



No 18 ga will not carry 5-6 amps : http://www.powerstream.com/Wire_Size.htm
it can only carry 2.3 amps for power transmitting.
i have fuses like this :
http://ecx.images-amazon.com/images/I/21G94RT1NvL._SL500_AA300_.jpg
and a fuse holder like this:
http://www.electronicsnmore.com/images/fuse-hl.gif
(i going to plug the battery into a breadboard and attach a fuse to it (to the breadboard)
but if 18ga wire can't handle 5-6 amps then could you suggest a fuse that would work:
with this battery :
http://www.all-battery.com/12v2600mahnimhbatterypack11620.aspx
with these motors connected to it :
http://shop.maxonmotor.com/ishop/article/article/222049.xml   x 3
http://shop.maxonmotor.com/ishop/article/article/2516.800-11.111-000.xml  x 1
and for this battery :
http://www.all-battery.com/6v200mahnimhsidebysiderxreceiverbatterypackswhitecconnectorforrcaircraftswalkingrobot-2.aspx
it's powering my micro-controller and my sensors.
please suggest a better fuses (what amp, slo - blow etc...)
i only want my fuse to protect the battery from frying up...
PS(sorry i ask so many questions it's just that this is my first robot project :P )

Thanks

Regards 
Jak24

Offline waltr

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Re: wires
« Reply #9 on: June 03, 2010, 02:53:16 PM »
Questions are good. I just try to get you to figured out the answers.

Look at the wire chart again. Power transmission means a very, very long piece of wire so it is the resistance and voltage drop that limits the recommended current to 2.3A.
Look at the column to the left titled "Maximum amps for chassis wiring". This is for shorter wires like on your bot. What is the max current under this condition?

Offline Jak24Topic starter

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Re: wires
« Reply #10 on: June 04, 2010, 10:52:12 AM »
Questions are good. I just try to get you to figured out the answers.

Look at the wire chart again. Power transmission means a very, very long piece of wire so it is the resistance and voltage drop that limits the recommended current to 2.3A.
Look at the column to the left titled "Maximum amps for chassis wiring". This is for shorter wires like on your bot. What is the max current under this condition?
it can handle 16 A ..... so with a 5-6A slow -blow fuse it should do the job? (the specs are in my previous post)

thanks

Regards

Jak24

Offline waltr

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Re: wires
« Reply #11 on: June 04, 2010, 12:24:21 PM »
Yep, you got it.

Offline Jak24Topic starter

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Re: wires
« Reply #12 on: June 05, 2010, 01:13:56 PM »
Hi

OK so any 5-6 amp(slow-blow) fuse for each battery (the 6v and 12v)
will stop any overloads or shorts right?
just making sure :D
Thanks
regards

Jak24

 


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