Author Topic: Electricity ?  (Read 2720 times)

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Chris333

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Electricity ?
« on: October 09, 2007, 05:43:54 AM »
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I'm still working on my Nn3 steamer. Tonight I put it back together again to give it a run and make sure it still works. I'm using Tech II dual power 2800. The back of the pack says Output 14.0 VDC and 8.5 VA.

The Nn3 steamer has a Faulhaber 8mm motor that is rated at 8 volts.

I figured the 14 volt output meant all the way cranked up. So half way on the knob would be 7 volts, seems logical. (to me) Just now I hooked up a volt meter and at half way on the power pack it reads 15 volts (as high as my meter goes) So by that logic full power would be about 30 volts.

What am I missing here?  ???

I just wanna to make sure I don't melt my $$$$ motor, but if I can't understand this much I need to stop and learn.

Chris333

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Re: Electricity ?
« Reply #1 on: October 09, 2007, 05:54:30 AM »
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Also just tried a "wall wart" that says output: 7.5VDC 350mA. My meter bolts up to 15v when hooked up. How is 7.5VDC = 15++++V ?

Thanks in advance for filling the void in my head.

kiwi_al

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Re: Electricity ?
« Reply #2 on: October 09, 2007, 07:19:34 AM »
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Hi Chris,
What meter are you using (Brand & type (Analog or digital) ) ?

Skip

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Re: Electricity ?
« Reply #3 on: October 09, 2007, 07:28:48 AM »
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Chris.

Most inexpensive power supplies, and sometimes the more expensive ones do not have a built in "load".  Therefore, what you are reading is the open circuit voltage.  Put the locomotive on the test track with the voltage turned all the way down and your meter in place.  Then slowly raise the voltage and see what you get.  This is the best way to set a voltage.


Chris333

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Re: Electricity ?
« Reply #4 on: October 09, 2007, 07:39:06 AM »
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My meter is old, a Micronta analog vom 22-212 radio shack special.

When I test right at the pack leads I get the same result as I do while touching the rails with the loco running. My motor may not have much of a load.

My motors specs are listed here:
http://www.faulhaber-group.com/uploadpk/e_0816S_MIN.pdf
It is the right column  008 S 8volt.

DKS

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Re: Electricity ?
« Reply #5 on: October 09, 2007, 08:11:51 AM »
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Chris--

First, test the meter. Take a 1.5 volt battery and see what the meter reports. Also try a 9 volt transistor battery. They should be within a few tenths of a volt from the value of the batteries. If they read OK, then your meter is at least fairly close to reality.

Here's the deal with power supplies. They are rarely filtered. Unfiltered DC consists of half-waves. These half-waves can peak between 50% and 100% higher the stated voltage. When the waves are averaged out (converted to filtered DC), the voltage drops down to somewhere near the target voltage. Meters may do a bit of averaging based on the inertia of the needle itself, but they can also register the peak voltage.

As previously noted, power supplies may also require a load before the voltage drops down to the target range. To protect a locomotive from damage, use an ordinary light bulb as a load. Connect the bulb to the supply, and meter across the bulb to see what is happening. Faulhaber motors do indeed have very low loads, so you may have a problem if the pack can't deliver the proper voltage. One way around this is to increase the load by connecting a bulb in parallel with the motor.

You may eventually want to invest in a better power supply to run Faulhaber and Z scale locos safely.
“Everyone leaves unfinished business. That's what dying is.” —Amos, The Expanse

Chris333

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Re: Electricity ?
« Reply #6 on: October 09, 2007, 08:33:27 AM »
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Ahhh just tested a bunch of AA 1.5V batteries and got about 4V reading, think I need a new meter.  :-\

About the power packs I mainly use a Control Master 20, but it is pulse power. I have read to keep pulse power away from coreless motors because it will cause them to overheat. Plus it's output is more like 18V.

I also have a Zthek controller, but I think I blew it up trying to rig it up to a power supply instead of batteries.
http://www.zthek.com/id64.htm

DKS

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Re: Electricity ?
« Reply #7 on: October 09, 2007, 08:46:25 AM »
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Yes, pulse = bad for coreless. Too bad about the ZThek.

You can get new meters cheap. I got one free when I ordered a soldering iron from some online dealer.

I'm also very interested in this: http://www3.sympatico.ca/kstapleton3/851.HTM
“Everyone leaves unfinished business. That's what dying is.” —Amos, The Expanse

3rdrail

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Re: Electricity ?
« Reply #8 on: October 09, 2007, 08:55:16 AM »
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Chris, have you checked the output of the Controlmaster 20? It is advertised as "pure DC", the exact opposite of pulse power. Should be a flat line on an oscilloscope. I'd like to know, too, because that is what I am using.

BTW, MRC is advertising the Controlmaster 20 again, see the back cover of the current MR.  ;)

Chris333

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Re: Electricity ?
« Reply #9 on: October 09, 2007, 09:11:52 AM »
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No use hooking my meter to the control master, it (the meter) just told me a almost dead 9v battery was putting out 15+v  ::)

I did look and it's out put is 14VDC for N/HO or 20VDC for O. I thought it was pulse the way it makes the Kato critter chassis run so much differently than a regular pack.

Ed Kapuscinski

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Re: Electricity ?
« Reply #10 on: October 09, 2007, 09:23:35 AM »
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Chris
Make sure there's not a sensitivity control on the meter.

It may be registering 1.5v as 15v, or 150v.

DKS

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Re: Electricity ?
« Reply #11 on: October 09, 2007, 09:27:27 AM »
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Does your meter have selectable ranges? Be sure the range you want is selected, and that you're looking at the right scale (assuming the meter has multiple scales, which most do). Also be sure the meter is matching the source, AC or DC (they will read very differently if swapped).
« Last Edit: October 09, 2007, 09:30:56 AM by dks2855 »
“Everyone leaves unfinished business. That's what dying is.” —Amos, The Expanse

Chris333

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Re: Electricity ?
« Reply #12 on: October 09, 2007, 09:32:45 AM »
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I have it set to the 15V range, it has 150 and 1000 as well. It is from the bottom of my old tool box and I mainly use it to test for shorts while handlaying track with PC ties.

Lemme go get a new meter. I wonder how many other times this meter has pointed me the wrong way...

John

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Re: Electricity ?
« Reply #13 on: October 09, 2007, 10:22:15 AM »
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Wally world has a good little meter in the automotive dept for under 10 bucks ... perfect for our uses.

Mark5

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Re: Electricity ?
« Reply #14 on: October 09, 2007, 03:15:05 PM »
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The Nn3 steamer has a Faulhaber 8mm motor that is rated at 8 volts.


I'm no electrical genius but have you considered installing resistors that limit the voltage to the motor to say 7.5 volts?

There's probably some folly in my idea, but hell that's what we're here for.  :P
« Last Edit: October 09, 2007, 03:18:41 PM by NandW »