AC Power Supply

[CNE Runner]

I didn't want to 'highjack' the thread on power supplies; but that dialog gave me an additional question. I run The Monks' Island Brewery/Railway with a DC handheld controller (Canadian made Jim). This controller, which is an excellent item, uses AC for power. As it now stands I used an MRC Tech II power supply (actually only the AC terminals on the MRC). This results in a rather large unit that takes up a lot of bench space for only its AC output terminals...'gotta be a better way.

I have checked all the 'wall warts' I can find and they all produce DC power only. Does anyone know of a fairly inexpensive AC-producing unit that is capable of outputting 12 - 18 volts AC; or am I stuck with using a complete model railroad power pack?

In keeping with the Forum's rules I will not mention the manufacturer of this throttle. Should you desire that information - contact me offline.

Cheers,
Ray

[richg]

How about 16 vac 1.2 amps?

http://www.allelectronics.com/make-a-store/category/815/Wall-Transformers/1.html

Other possibilities. A search for wall transformer seems like a better search.

http://www.google.com/search?pz=1&cf=all&ned=us&hl=en&q=wall+transformer+16vac&btnmeta%3Dsearch%3Dsearch=Search+the+Web

Rich

[Joe Satnik]

Dear Ray,

http://www.bachmanntrains.com/home-usa/products.php?act=viewProd&productId=209

I have these wall-wart transformer and controller (power pack) combos new from set break-ups.

Contact me PM (click on my name - personal message) for more details.

There are two ways to get the wall-wart transformer's 16V AC, 1 Amp output:

1.) Non-protected directly from the transformer output plug, or

2.) Circuit-breaker protected (1 amp) through the two Push-Insert (wire)-Release terminals on the controller.

The only way I would use method 1 would be if I were certain there was circuit breaker (or some other form of current limiting) protection on the input of your throttle.

Again:

You must have/use some form of current limiting device...

The transformer itself does have an internal non-replaceable fuse, but if you blow it, you toss it in the recycling bin for its copper content....

Hope this helps.

Sincerely,

Joe Satnik  

[CNE Runner]

I sincerely appreciate the input to my thread's question. RichG, I checked out the websites you suggested and found at least a couple of wall transformers that would (on the surface) work for my application. What troubles me is the statement that warns about power fluctuations: [sic. 'output depends upon demand. At no to lower levels of demand voltage output is greater than specified (16 VAC with little or not load can approach 20 VAC); while higher demands lower the stated output (16 VAC can become as low as 10 VAC under certain conditions)']. According to the specification sheet, for the handheld throttle, voltages must remain in the 12 - 18 VAC range.

I would assume the same thing happens when connected to the AC terminals on my MRC Tech II power pack (ie voltage fluctuation vs demand). Fortunately I have an acquaintance with a retired aero-space electrical engineer and will run the problem past him. Before I do so (or order a wall transformer) I have to determine the power demands of my Bachmann MDT and Trackmobile.

Thanks again to all. Joe, I appreciate the offer of the controller/transformer sets...I have an excellent handheld throttle. Your caveat on making sure there is over current protection is a good one and will be followed.

Regards,
Ray

[richg]

An AC wall wart will not have regulated voltage. It all depends on the amps the xfmr can supply before the voltage level begins to drop some.
A xfmr that supplies 200 ma and you draw 150 ma, the voltage will drop some. A xfmr that can supply 3 amps, the voltage will not drop much with with a 150ma load. Ohms law.

Some DC wall warts are not regulated. Some DC wall warts are regulated.

Rich

[Joe Satnik]

Ray,

How many amps max does your hand-held draw? 

Voltage output @ Current draw measurements from Bachmann wall-wart transformer (nominally 16V AC @ 1 amp):

17.08 Volts RMS~ @ 0 Amps (open circuit)

16.3 Volts @ 0.466 Amps

15.8 Volts @ 0.684 Amps

15.3 Volts @ 1.093 Amps

Secondary winding resistance (DC) ~1.1 Ohms.

Internal impedance (estimated from first and last measurements above) ~ 1.6 Ohms.   

Model:

   l-------------------1.6 Ohms Imp.-------->
   l
17.08 V RMS ~                              Secondary Output   
   l
   l----------------------------------------->

Hope this helps..

Sincerely,

Joe Satnik