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steam5

Australia

Brakeman
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12/03/2008 9:55 PM
I’m trying to source a suitable transformer or power supply for a Lenz LZV100 (the command station from there Set-100 and Set-90). The max voltage must not be more than 18V AC, the instructions don’t say at what DC voltage but I’m guessing about 16VDC??? I live in Australia so I need s supply which operates from 230VAC and it good for at least 6Amps. I was told not to use a switch mode power supply, would anyone know why? Can anyone suggest a transformer or power supply? I’m competent with wiring at mains voltages as well.

Dan Pierce User is Offline

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South Eastern MA, USA
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12/04/2008 5:01 AM
Multiply 18 volts by 1.414.and that would be the peak voltage presented to the inpput of the diode/rectifier circuit. Subtract a 1.4 volt drop from 2 diodes and this would be the maximum DC voltage to a storage capacitor. So 18 times 1.414.gives 25.452, minus the 1.4 for the diodes and you get 24.052. So , 24 volts would be the max. Be careful here as some 24 volt supplies are for car type batteries and the math is 25.2 which is too high. (6.3 times 4 or 12.6 times 2). A regulated computer type supply is needed for 24 volts. Aristo has an Elite at 22.5 volts, or the everest at 24.0 and are regulated to those voltages. These supplies are smart power and operate at 100 to 240 volts. The statement about switch mode supplies is for those that may be poorly regulated and noise creeps through thus impeding the Lenz operation. A good supply should not present any problem.

Road Foreman User is Offline

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12/04/2008 8:08 AM
Follow Dan's guide lines.. If you use a transformer get 1 that is about twice the current rating as needed.. This will help with votage sag @ high curent draw.. I would use the regulated power supply.. Mean-Well is another good brand.. Digitrax has the PS2012 regulated power supply, 23 volts @ 12 amps.. For transformers go here for 1 brand http://www.hammondsales.com/pdf/section7.pdf I think NCE say to use this brand for there DCC systems.. Hope this helps.. BulletBob

Bob Burton

Greg Elmassian User is Offline

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Carlsbad (San Diego), CA

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12/04/2008 9:58 PM
I am getting much better performance since I switched from an ordinary 10 amp ac transformer to a regulated DC supply. I needed 27 vDC to get 24V DCC to the rails with my NCE system. I would not recommend the Everest supply, email me privately if you need the reason. Regards, Greg

Be sure to visit my site, lots of technical tips and modifications, and you can search for topics and key words. Click here for Greg's web site

StanleyAmes User is Offline

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12/05/2008 9:02 AM
I share Greg's recomendation. I use the AristoCraft 10 amp switching power supply (which supports 110 and 220). One of the real problems is heat disapation when the voltage at the track is different they the voltage of the supply. With a switching power supply you can set the the two to be as close to each other as possible and thus reduce any unnecessary heat of voltage sags. Stan Ames www.tttrains.com/largescale

Greg Elmassian User is Offline

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12/05/2008 10:23 AM
Thanks Stan, I overlooked that facet, and you are right, you can actually wind up limiting your system output because you are asking the booster to "waste" excess input voltage. (adding heat to the system just to "drop" the input voltage down) Regards, Greg

Be sure to visit my site, lots of technical tips and modifications, and you can search for topics and key words. Click here for Greg's web site

gwschreyer User is Offline

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12/05/2008 11:26 AM
The rectifier drop will be the same with either AC or DC input so that maximum DC input would be 1.41 x VAC or about 25.4 VDC. For a DC input, the power suppiy's output current capability should be about the same as the booster's trip current capability plus a little to cover the parasitic loads of the booster. For an AC input, the transformer's current capability should be about 1.6x the booster trip current. This includes the parasitic loads of the booster. Some sag is allowed in the power supply voltage, this is taken up by the booster regulating it's peak output. Sag is expected at trip current levels, do not worry too much about sag at current levels beyond the booster rating. If you do run a very high input voltage and regulate the booster at HO output levels, the booster will get hot. Use an input voltage about 4 volts higher than the voltage that you want on the track and then adjust the booster to that level. If your input is AC, the input voltage to be concerned with is the PEAK (1.41 x RMS). A Digitrax 8 amp booster (at least the old one that I have) actually trips at less than 7 amps at the output. Newer ones might be better A PB110 (old one) trips at 20 amps. I believe that the newer ones are about the same. It is important that whatever power supply that is used can handle the trip current of the booster. If the power supply current limits early, the booster will not be able to trip and protect itself UNLESS, the power supply itself trips completely off in which case the power supply itself is providing the protection. If the power supply just current limits at a constant current and that current is too low, the booster is at risk. The 110/220V thing has no particular meaning. Whatever power supply that you use has to be set up to run on whatever line voltage that you have.

- gws

steam5

Australia

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12/05/2008 3:59 PM
Thanks for the tips! I have emailed Lenz asking what there max input DC voltage is, trust me I believe you guys, but just want to make sure! I have always thought a regulated supply would have been best, but the same person who told me to not use a switch mode told me an AC transformer was best. Still not sure why someone told me to not use a switch mode power supply, but noise could have been a reason. When I test my HO equipment on the bench using a Lenz system I use an old Toshiba laptop power supply, which is a switch mode and it works well, form memory its 12V and good for 1.5A, perfect for HO.

gwschreyer User is Offline

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12/05/2008 7:12 PM
if the power source has the grunt to do the job, it won't matter if it is AC, non-regulated DC, regulated DC or switchmode regulated DC. Remember that your booster is also a rectifier, filter and regulator. All you are providing is raw power. It will do the rest.

- gws

Greg Elmassian User is Offline

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12/05/2008 7:40 PM
There's a lot of hooey going around about "pure dc power". DCC systems don't have any problem with any minimal ripple from a switching power supply. DCS, from MTH, is apparently much more sensitive. Noise from switch mode power supplies USED to be a problem about 20 years ago. Old superstitions die hard. Regards, Greg

Be sure to visit my site, lots of technical tips and modifications, and you can search for topics and key words. Click here for Greg's web site

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