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PCB switches for BPRC
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 Posted: Fri Mar 10th, 2017 09:39 am
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davecttr
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I am starting a new project this year to convert a number of diesel locos to BPRC using NiMH AAA batteries. I want to have a switch in the loco and have some of these  little switches. I hope to solder them to a breadboard so both switches operate on the same wire! I will be using 4.8V via a 9V Pololu regulator with the locos needing about 0.3A with some up to 0.5A. will they take the load?
http://www.technobotsonline.com/excel-2-way-4-pin-dil-switch.html



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 Posted: Fri Mar 10th, 2017 09:53 am
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Rod Hutchinson
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I use these to isolate the receiver from the battery when charging.

Last edited on Fri Mar 10th, 2017 09:54 am by Rod Hutchinson



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 Posted: Fri Mar 10th, 2017 11:11 am
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Helmut
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davecttr wrote: .. have some of these  little switches. .. will they take the load?
http://www.technobotsonline.com/excel-2-way-4-pin-dil-switch.html
If you'd read the specs listed underneath - explicitly:"Contact rating: switching 25mA 24V dc, non switching 100mA 50V dc"
Your anticipated currents are much too high.



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 Posted: Fri Mar 10th, 2017 11:38 am
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davecttr
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How do you calculate the anticipated currents?



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 Posted: Fri Mar 10th, 2017 12:03 pm
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davecttr
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As a bulkier alternative I have dozens of these recovered form my old cab control layout
http://www.technobotsonline.com/spdt-miniature-toggle-switch.html
the lettering on mine is:
2A at 250V AC5A at 120V AC
or I could just use manual switches made from SIL sockets and plug in cables



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 Posted: Fri Mar 10th, 2017 12:25 pm
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Helmut
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Well, you write about Im=0.3..0.5A motor current. The stepup has an efficiency of E=0.85..0.9 in this range. The stepup ratio is 1:1.88, that is ( Im*1.88)/E, resulting in 0.6..1,1A battery current the switch has to bear. The one you chose is OK, but there are slide switches around that may fit even better: e.g. this one

Last edited on Fri Mar 10th, 2017 12:28 pm by Helmut



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 Posted: Fri Mar 10th, 2017 02:41 pm
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Si.
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Hi Dave :wave:


I Posted some stuff about these switches a couple of years back ... somewhere ?

They have all been available as standard O.E.M products in electronic-design FOR YEARS.

If you ever need a replacement (which you won't) they are easy to get.













:moose:


Si.




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 Posted: Fri Mar 10th, 2017 02:54 pm
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Si.
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They are all available from cpc.co.uk


If you spend £5 ex VAT they do FAST and FREE delivery.


When you order, get them to send you the 4000 page paper catalogue.


It saves bumbling around online for hours & hours and has ZILLIONS of cool goodies in it !


You could end up a pauper though ... trust me ! ;)


:moose:


Si.


I have used & still do use other suppliers, such as R.S. and Farnell etc.


But in many ways cpc.co.uk is ALWAYS the first place to go, for choice, price, FREE delivery and quality, repeatable components.


TONS more switches, unusual battery holders, rechargable cells, tools, consumables, radio control gizmos.


It is IMPOSSIBLE not to spend a 5er, the FREE shipping pays for itself QUICKLY compared to other suppliers often £4  £5  or sometimes more P&P charges.



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 Posted: Sat Mar 11th, 2017 08:53 am
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davecttr
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Thanks Si I will have a look at CPC



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 Posted: Sat Mar 11th, 2017 02:10 pm
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Si.
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Hi again Dave :wave:



I looked into sources of 'small', relatively HIGH-CURRENT options, and that is the 'key' with these small-switches, a couple of years back.


I have a stack of electronics-catalogues big enough to reach stuff on high shelves ! ;)


These are the ONLY three that I came up with as a short-list, which really offer that kind of performance & reliability.


All 3 have very 'positive actions', with in-built springs being the secret here.


They DON'T rely on 'friction' as most of the cheapo ones do.


These 'friction' ones are in my experience, the type that is crimped & folded etc. on to a tiny piece of S.R.B.P board, and are typical of old, cheap stereos & consumer products.


The 'friction' goes loose with use & the switch just goes dicky.



Switch 1. is a great choice for frog 'polarity switching' using Caboose Industries HO switch-stands.

The 'throw' is exactly right.

The 3 different lever-types are quite helpful of course too.



Switch 2. really is VERY SMALL, the two different angles pretty cool to have for different circumstances.

It has a light, positive action.

High current spec.

The actuator has a slight 'depression' in the end & can be operated with a pencil/pen etc. useful !



Switch 3. Only 1 type is shown, out of the 4 different lever kinds.

This has slightly higher contact-resistance than the other two.

I think personally, that the spec. given is a bit conservative & that the switch will in fact handle more current than might seem the case from 'the theory'.

I have used this on a professional-product & never had a single failure.



Hope that helps.


cpc.co.uk really is a great place for the professional & hobbyist alike to order from.

Once I discovered them some years ago, the way I bought & used parts RADICALLY changed, due to the diversity of products generally that they stock.

& yes, everything is 99% of the time ACTUALLY IN STOCK.


:moose:


Si.



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http://www.freerails.com/view_topic.php?id=7318&forum_id=17&page=1

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http://www.slotforum.com/forums/index.php?showtopic=59295&st=0&a
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