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Discussion Starter · #1 ·
I am using Kadee couplings for my new layout. I have previous experience with them and have found they work reliably almost all of the time. I have just bought an electro-magnetic uncoupler and have discovered that it requires 16 VDC at least 1.5 amps or 18VAC with a rectifier for DC also at least 1.5 amps.

I have two double power units converting mains supply to 16 VAC at max 1 Amp or and old controller supplying 12 VDC.

Will the uncoupler work at all with my present supply or I will need to buy a power supply supplying 16VDC/18VAC?

Thanks in advance

David
 

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Discussion Starter · #3 ·
Sol. That is strange. On the 309 packet which I have in front of me it says quite clearly, "We recommend a 16 volts DC power source (at least 1.5 amps) or 18volts AC (at least 1.5 amps) converted to DC with bridge rectifier."

I'm more confused than ever.

David
 

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Then I suggest you contact Kadee direct and point out the differences.

I know when I bought one years ago it was the #307, it wasn't until I got the packet & what it required and that info was not on the website so I advised them so they updated the site.

Kadee - The Coupler People

I just read the 309 instructions & they say 1.5A
 

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Sol. That is strange. On the 309 packet which I have in front of me it says quite clearly, "We recommend a 16 volts DC power source (at least 1.5 amps) or 18volts AC (at least 1.5 amps) converted to DC with bridge rectifier."

I'm more confused than ever.

David

Buy a circa DC power brick with enough amps. I could buy a 15v 3A "brick" for £11, that will do the job.

Your 1A transformer based supplies will not deliver enough current, and the voltage will then drop away when the coupler is turned on.

In terms of wiring, think about the back-emf from the coil that occurs as the power goes to "off". That will burn out many push button switches pretty quickly. There are two solutions: a diode wired over the coil to "squelch" the back-emf (cheap, simple), or use a MosFET switch module (couple of pounds from ebay/amazon). The MosFET module means the wiring to any panel is very low current (so don't need high current switches on panel, don't need fat wire to panel), the only high current is in the supply to the coil.
 

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Discussion Starter · #6 ·
Nigel Many thanks for your info but I confess I'm more confused than ever. In one place Kadee say the 309 needs16 VDC and at least 1.5 amps, in another 16VDC, 3 amps. Now you're saying that 15V, 3A will do the job but only if I wire in a diode or switch module neither of which I'm familiar with. I have heard of back emf but have no idea of its significance. I'm aware of high current as in supplied by the mains but am not sure what 'very low' or high current means as applied to railway wiring.

Its sounds as if I either need a course in basic electrics or I go back to permanent magnets.

Many thanks again for taking the trouble to reply

David
 

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Discussion Starter · #7 ·
I've just heard back from Sam at Kadee who says "at least 1.5 amps, no more than 3 amps." I pointed out that it would be helpful if it said that on the package and website.
 

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I used an 18 volt, 3amp supply for mine, but didn't think of the diode that Nigel mentioned. What diode would you recommend, Nigel and do you mean across the wires when you say over the coil?
Sorry to butt in but I'm now worried that my sprung to centre off toggle switches might burn out.
 

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Current of power supply. It doesn't matter, so long as its more than the minimum needed to operate the coil. Thus 1.5A, 3A, 5A, 10A, 30A would all be fine from the coil's point of view. The coil will just draw as much power as it can cope with (about 1.5A), the remaining power is just sitting around for use by other things which could operate at the same time. A supply of between 1.5A and 3A for the coils is sensible - enough power for the job without being excessive. ( Fitting a larger current power supply means wiring needs to be adequate to cope with the potential current available, or risk wires overheating, plus it costs more money.).

Volts. For a simple coil used as an electromagnet (which the device is, its just a coil of wire), a volt or two won't matter. 16V vs.15V will be pretty much undetectable in coil performance.


Diode, to protect switch from spark erosion. One which carries enough current, so a 3A or 5A rectifier diode. Fit the diode near the coil, in parallel to the coil (ie. one leg of diode to one terminal on coil, other leg of diode to other terminal of coil), oriented so the diode does not conduct when the operating switch is on. With most common diodes, that means "end with band to the positive wire ". (if you get it the wrong way round, the diode will short-circuit the power supply, and the coil gets no power and doesn't work).




- Nigel
 
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