Wire sizes

Nine Elms
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Wire sizes

#1

Post by Nine Elms »

Oh no not another "round" of sizes of wire I hear you say, but please bear with me.

As a retired mechanical engineer the concept of the "right size bolt for the job" I can cope with, but "right size wire for the job" is still beyond me!!! I am trying to wire a surface mounted points "motor" and not sure what wire to use. The wires coming from the "motor" are very thin. Do I solder the same size wire running back to my control panel or up the size, if so what size?

Am I right in thinking that electrical wire is a bit like hose pipes. For the same flow rate of water, the smaller the diameter the greater the resistance.

From a complete novice trying to learn.

John
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Brian
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Re: Wire sizes

#2

Post by Brian »

Hi
General rule of thumb for wires is you cant really have too larger size of wire other than they can present a problem connecting their ends into smaller items. But too smaller wire size leads to problems due to wire run length and volt drop.

My recommendation for any type of solenoid point motor is to use as a minimum 16/0.2mm equipment wire for all three wires and the feeds to switches /levers. Simplest and possibly the easiest is to shorten the pre fitted wires to around 6 inches long and connect these into a three way piece of 5 or 6 Amp terminal block fitted underneath the layout. Example... https://www.toolstation.com/connector-strip/p88321
From the other side of the terminal block two 16/0.2mm wires run back to the lever or switch and the return which is shred with all other motor returns runs back to the supply or the CDU negative output.

Note where a pair (or more) of solenoid motors move together - e.g. a cross over pair of points then consider increasing the common single return wire that connects to all point motor returns to 24/0.2mm or even 32/0.2mm where more than two move at once. I also recommend running each motors two operation feed wires individually from their operating switch or lever, as this then gives each motor a better chance of operating correctly.

Finally, consider if you haven't one already, to use a Capacitor Discharge Unit (CDU) as this will give a improved pulse of power to all the motors and also prevent accidental motor coil burn out should a lever or switch be left in the On position for too long. Ideally feed the CDU from a 16 volt AC power source. Note the Hornby Black R044 point lever doesn't work well with a CDU due to its very old design. But all others do, including the Peco PL-26 lever. Use Toggle switches of the momentary type - Sprung to centre off or are often called (On)-Off-(On) type.
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Nine Elms
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Re: Wire sizes

#3

Post by Nine Elms »

Thank you Brian this very helpful. I am planning to use On-Off-On toggle switches. A supplementary question; Can I use single core wire size approx 1.00mm?

John
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Rog (RJ)
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Re: Wire sizes

#4

Post by Rog (RJ) »

As Brian has indicated, the switches must be of the non locking, sprung to centre off variety (on) off (on) to prevent the motors from being powered for too long. The brackets indicate the non locking action. The point motors can burn out in just a few seconds.

Solid core wire can be used but it is susceptible to breaking if it is subjected to vibration, so it needs to be secured to prevent it moving about.

Edited for clarity.
Nine Elms
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Re: Wire sizes

#5

Post by Nine Elms »

Sorry to be a pain, but can you tell me the correlation between say 24 SWG and 16/02 wire? I am trying to buy some suitable wire but can only see SWG size.

Confused Mechanical Engineer, John
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teedoubleudee
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Re: Wire sizes

#6

Post by teedoubleudee »

Nine Elms wrote: Tue Feb 09, 2021 2:36 pm Sorry to be a pain, but can you tell me the correlation between say 24 SWG and 16/02 wire? I am trying to buy some suitable wire but can only see SWG size.

Confused Mechanical Engineer, John
John, go to Bitsbox. Their wire is described in wire number/size eg 16/0.2 etc. It's good stuff, sold by the meter and comes in plenty of colours. Fair delivery price and quick turn around. I use them all the time for basic electrical bits. No affiliation, just satisfied customer.

https://www.bitsbox.co.uk/
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Brian
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Re: Wire sizes

#7

Post by Brian »

Nine Elms wrote: Tue Feb 09, 2021 2:36 pm Sorry to be a pain, but can you tell me the correlation between say 24 SWG and 16/02 wire? I am trying to buy some suitable wire but can only see SWG size.

Confused Mechanical Engineer, John
Taken from my web site... Its as near as possible conversion..
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I agree with TDD If you're UK based then Bitsbox is a good supplier, https://www.bitsbox.co.uk/index.php?mai ... th=200_203 other places include eBay for equipment wire, typical example https://www.ebay.co.uk/itm/Equipment-Ho ... Sw6odftUcp
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Nine Elms
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Re: Wire sizes

#8

Post by Nine Elms »

Thank you all you have been most helpful.

John
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Stese
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Re: Wire sizes

#9

Post by Stese »

If you've already got the locking switches, abd you don't wabt to buy new, you can still use them, with a minor alteration to your wiring.

simply add a push-to-make momentary button in between the cdu and the feeds to the switches. This then prevents a permently connected, damaging the motor and cdu.
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Brian
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Re: Wire sizes

#10

Post by Brian »

Simplest I feel is to use the correct type of switch in the first place, which is a sprung to centre off type (On)-Off-(On).
If you're ordering wire from Bitsbox the correct toggle switches are these https://www.bitsbox.co.uk/index.php? ma ... cts_id=876 Their item No SW112.

Relying on a PB and all other point operation switches being in their middle Off position is a bit hit and miss IMO! It can lead to failure to throw especially where one or more switches have been left in the On position as the CDU is then discharging into several point motor coils all at once! :o But it will work so long as all switches are returned to their middle off positions!
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