OK, last time I am asking, I keep forgetting to book mark the answer. This time I will copy and paste the answer. Want to make sure the motor is good for DCC use.
I have a Harbor Freight Ohm Meter and using a small Rail Power 1100 Transformer.
1 What settings do I use on the Ohm Meter and hook the leads too?
2 How to I hook the leads to the motor from the transformer and the leads on the ohm meter?
3 Free running amps should be? Will be out of the chassis.
4 I should stall the motor,correct?
5 I think I should not be over 1.35 amps fully stalled, correct?
Beginning to think it is time to retire my aging fleet motors, but I just want to double check before I replaces them.
Thanks Again, Cuda Ken
I hate Rust
Ken,
Check to see if your meter has an AMP or MA position. Mine has a 10 amp and 200 ma position for DC Amps. You want to place the meter in SERIES - no parallel to the motor. you need to cut it in between one of the power pack terminals and the track. The other power pack terminal will got to the track like normal.
Usually most older motors will draw .5 to 1.0 amps if the engine is free running. I have seen some older engines draw 2 amps. Most of my older Athearn BB engines drew about .6 to .75 amps when running. The 'stall' current was usually around 2 amps.
Most HO decoders will handle 1.5 to 2.0 amps for a short time(like at stall), and will handle a full amp when running - check the documentation with the decoder.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
You could kill two birds with one stone. Tie a string to offending tooth, run loco and measure current draw during the stump pulling session
Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum
Keep the power pack at full throttle. If you have the $2.99 meter, you have to use the 10 amp range, and plug the leads into the right terminals ont he meter - there's a different place to plug the red lead for the 10 amp range, and is used only for the 10 amp range. It will be accurate enough.
Meter goes in series with the track power. Powerpack -- meter -- rail 1 ---<loco on track> -- rail 2 -- power pack
Stall loco briefly and read current. Easiest thing is to grab the flywheel on a loco so equipped. Don't hold it too long, just enough to get a reading on the meter. Any decoder thatn can handle the measured current or higher will work. If the only decoders that cna handle the current end up being G scale decoders, consider a replacement motor.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
cudaken OK, last time I am asking, I keep forgetting to book mark the answer. This time I will copy and paste the answer. Want to make sure the motor is good for DCC use. I have a Harbor Freight Ohm Meter and using a small Rail Power 1100 Transformer. 1 What settings do I use on the Ohm Meter and hook the leads too? 2 How to I hook the leads to the motor from the transformer and the leads on the ohm meter? 3 Free running amps should be? Will be out of the chassis. 4 I should stall the motor,correct? 5 I think I should not be over 1.35 amps fully stalled, correct? Beginning to think it is time to retire my aging fleet motors, but I just want to double check before I replaces them. Thanks Again, Cuda Ken
Lets keep the terminolgy accurate to prevent confusion.
You have a Harbor Freight multimeter. The multimeter has an ohm meter function, AC & DC voltmeter function, plus DC amp meter function. There are three other minor funtions I never use. I have three of these meters for some years. All my meters came with simple manuals but are adequate.
Measuring stall current.
http://www.mrdccu.com/curriculum/stall.htm
Always start with the 10 amp position.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
cudaken 3 Free running amps should be? ... 5 I think I should not be over 1.35 amps fully stalled, correct?
OK, thanks for the answers, but you missed one detail. Motor will be out of the chassis.
I tried last night to test a motor, hooked a power led from transformer to the top brush clip with a alligator clip.
Hooked the other transformer led to a led on the Ohm Meter and then touched the other Ohm meter led to the bottom brush clip, got nothing. Motor did not even hum.
But, I think I might know what I did wrong. I did not have the red led in the 10ADC plug. I had it in the V mA (don't have the other symbol that would go between the V m) Was that why I did not get a reading?
Simon, hum that was helpful
Thanks for all the answers folks
Ken
There is a protection fuse in these meters in case you try to draw too much current though the meter.
The fuse is a 0.25 amp fuse and yes, the fuse in mine has a piece to aluminum foil around it.
I cannot remember if the fuse would affect the ten amp scale. It has been a couple years since I put the foil around the fuse. I was using the 200 ma scale and measuring an old open frame motor. Forgot to switch the red test lead.
You will need a 5 x 20 mm 0.25 amp glass fast acting fuse. The Shack sells them.
The cheap meter has no fuse on the 10A line, although I think it has a fusible link so if you tried to run 100 amps through it it wouldn't blow up in your face. Only the mA connection has a fuse. Pretty sure that will mean the ohms and volts won't work anymore, but the 10A should work.
My first one, the battery finally died. I have to see what those batteries cost, if it's more then $2.99 I'm just getting a whole new meter and I'll see if I can do somethign neat with the dead battery one. Maybe add an integrator circuit and make a proper DCC volt/amp meter out of it, powered by tthe circuit it's testing. Funny thought - I was thinking rotary switch to couple it to each of my 4 power districts - but it might be cheaper just to get 4 whole meters. LOL
These meters use a regular 9 volt battery. I took a LM317LZ, 200 ma regulator, two resistors and a couple electrolytic caps and made a 9 volt regulator. Tied into the 12 vdc buss for accessories and have a switchable voltmeter for the layout. I have a well equipped junk box from years of electronic projects.
A alkaline 9 volt battery for these meters will last a long time.
For some reason I thought it used some oddball button type battery, not a plain old ordinary 9V. Well, good news, even a $2.99 item is not disposable (I have 2 or 3 others anyway - keep on in my car, one in my train toolbox, and one in my desk. I think there's one in with my electronics cabinet for the layout as well)
Just tested it the right way. When cold the motor free wheeled at .95 amps and stalled at 1.14 amps. Got the motor hot and free wheeling went down to .75 and stall was at 1.14 amps.
So I should be good to go, right?
The no load, motor running current is way too high. Either the current measurement is wrong, or the motor is in bad shape. Installed in the engine, with no cars attached, most motors will not draw more than 0.6 amps, even old Athearn open frame. A can motor - engine by itself - should be in the 0.3 amp range.
Stall current seems pretty reasonable. What does bother me is being able to get the motor hot not installed or loaded. Unless you are stalling the shaft, an unloaded motor should not be getting hot under any circumstances.
If you readings are correct, and I understand the situation correctly, you need new magnets and/or re-motor.
Fred W
Something's definitely wrong there, that's too much current for the motor turning freely without any drive train attached. Besides the already mentioned potential issues, there could also be a partially shorted winding. That could explain the heating - and it this motor blew a decoder before, that could be why, even though neither reading exceeded the decoder's rating.
Here is the cheap meter some of us use. They come in orange, yellow and gray cases. Probably made by one company in China. Very inexpensive to replace if you burn one out.
Runs on one 9 volt battery that last quite some time.
I looked at the insides a little closer. There is a shunt between the Common terminal and the 10 amp terminal that bypasses most of the current. A small resistor picks off a small amount of voltage for measuring. My test meter shows about 0.05 ohms for this shunt.
The fuse is only for the 200 ma terminal.
Looks like someone blew their fuse - is that tinfoil around it?
Going to retest the motor later tonight and double check my readings. I all so have some motors Model Maker sent me and test what there power draw is.
All so may try shorting the brushes and cutting the springs down some.
Randy, how do you test for a bad winding?
Open Frame, that when you can see the brushes, right? This one is a Athearn Ready To Repair.
To test for a shorted winding, youhave to take the motor apart. This WILL further weaken the magnetic field on an older motor. You need a fairly low ohms setting ont he meter scale, and measure each commutator segment to every other, all combinations, all the way around. They should all be close, and definitely NOT 0. A totally shorted one will measure 0, a partially shorted one will read something lower than all the other ones do. A broken one will be infinite ohms - open circuit. Unless you want to try your hand at rewinding a motor, it's not really fixable.
rrinker Looks like someone blew their fuse - is that tinfoil around it? --Randy
Yes blown fuse I mentioned a few messages back. Happened about two years ago when I was testing an old open frame motor and was still in the 200 ma scale. I should get to the local Shack and get some 5mm x 20mm 0.25 amp fuses. There is a Shack about five miles from where I live and will use my bicycle on the local rail trail tomorrow and pick up some fuses.
Ric h