My thoughts:
Only a very small percentage of model railroaders ever bother to check their locomotives' current consumption or even just the drive train for excessive friction and binding. Either action would save the motor in almost all cases.
my thoughts, your choices
Fred W
For a motor decoder? Actually not. The cpu is a signle chip most of the time. In fact I have a link to a DIY decoder that gets all soldered around the CPU chip (in that case a Microchip PIC). Insane. Motor drive is usually 2 'chips' one that has the trnasistors for the top half of the H bridge and a second that has the opposit epolarity transistors for the bottom half. Function output is usually one transistor per output (technically not 'outputs' since they are current sinks). Input is usually 4 fast rectifier diodes. Sorry, I misread rectifier as regulator, there usually is a regulator but obviously not for the motor. Plus the required resistors an capacitors for bias and stabilization. Decoders are amazingly simple, actually. Now if we're talkign about SOUND decoders...
Here's the super tiny DIY one: http://www.fremo.utwente.nl/selfmade_decoder/decopic_e.html
Guy's nuts, if you ask me. But if it works...
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker Just one thing about that decoder block diagram - the motor drive does NOT come from the voltage regulator. That tiny surface mount regulator isn't rated to handle the typical 1.5 amp continuous/2 amp momentary motor drive capability of typical HO decoders. Heck a full-size LM78xx in a TO220 package can only handle 1.5 amps - WITH a heatsink. Typically 1 amp or less with no heatsink added. The motor drive DOES pull from after the rectifier bridge to get DC. --Randy
Just one thing about that decoder block diagram - the motor drive does NOT come from the voltage regulator. That tiny surface mount regulator isn't rated to handle the typical 1.5 amp continuous/2 amp momentary motor drive capability of typical HO decoders. Heck a full-size LM78xx in a TO220 package can only handle 1.5 amps - WITH a heatsink. Typically 1 amp or less with no heatsink added. The motor drive DOES pull from after the rectifier bridge to get DC.
Hello Randy
Who said anything about a voltage regulator? There is no voltage regulator in the diagram. That diagram is not a diagram of a complete decoder. The diagram does not show all the DC and digital paths. The center box consist of probably three or four chips.
One chip is a uCTRLR a micro controller.
One a ROM
One a RAM
One an eprom
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.
Here is a link to decoder waveforms. Store this in you Favorites folder. In fact you might store this page in your Favorites folder. Eventually this thread will be buried.
Yes, with a voltmeter you will see DC voltage on the motor terminals. An Oscilloscope with show the pulses. For reverse, minus 12 volt pulses. I have done that.
On the track, you will see AC volts with the meter and plus 12 to 14 to minus 12 to 14 volt pulses for a range of 24 to 28 volts peak to peak with the scope. It also depends on the DCC controller.
http://www.awrr.com/dccintro1.html
Assuming the decoder was properly installed and the decoder wasn't damaged or anything, I'd think the motor was the problem, not the decoder.
Sorry, I missed the part about the 44 tonner. I suspect a motor failure was not caused by the DCC. These things are made in China and no telling what the quality is like. I belong to the Bachmann forums and some other train forums and I see quality issues with Bachmann products occasionally.
At least Bachmann has a somewhat decent product warranty.
The output of a DCC decoder is a pulse width modulated signal (PWM). As Rich stated, the pulse is at the full voltage (based on track voltage, it's not regulated to 12 volts, but with the typical 14 volts or so most DCC systems put on the track for HO, minus the drop in the switching transistors, it ends up at about 12 volts), and the wider the pulses, the faster the motor turns. Early, and super cheapy decoders still made today, used a pulse frequency within the audible range, so dependign ont he motor you could hear it buzz or sing. This was also bad for coreless can motors (not all can motors are coreless - coreless motors are a special type, very smooth but also very expensive. But if you want the best in your loco...). Most modern decoders use a high frequency or 'silent' drive with a much higher pulse frequency. This serves to keep the motor quite, and also keeps coreless motors from overheating so you shouldn't fear using them with DCC if you have a 'silent' decoder. The downside of high frequency pulses is poor low speed torque - just when you need it most to get a train started. Enter in various names for the same thing - torque compensation being a common one, which is a decoder settign to give an extra boost at low speed to overcome the lack of torque fromt he high frequency pulses. There's no such thing as a free lunch - high frequency is quiet and safe but needs some extra help at the low end. Low frequency starts trains just fine but makes regular motors run hotter and is completely unsuitable for coreless motors.
A motor being run by a decoder sees 12 volt positive pulses for forward and 12 volt negative pulses for reverse. The wider the pulses, the faster the motor turns. For stop, no pulses.In other words, the motor is turned on and off at a certain frequency.
Even if the decoder is under DC control, the motor still sees pulses.
With the older decoders, the frequency was low enough that some motors would buzz a little but not near as bad as a motor under stretch zero control.
Unless you're talking about a DC locomotive with no decoder, you have it wrong when you say that DCC turns the motor on and off. With DCC and a decoder equipped locomotive, the decoder sends a constant voltage to the motor.
Having a DC locomotive on a DCC track can quickly overheat the motor because the track has a high frequency AC square wave at 14.5 volts or thereabouts, causing the motor to buzz and generate heat.
Trying to run a DC locomotive using DCC address 0 is a gimmick that the NMRA came up with in the days when decoders cost $50 or so, and is hard on the motor and can burn it out if you run one too long in this mode because the DCC system is, in this case, turning the motor on and off very rapidly, which generates heat.
If you have a can motor as a replacement it is well suited to operations using DCC. I don't know enough about the effects on other types of electric motors and their drives, but all modern engines have can motors. I have run diesel and steam HO models for a few years now with several different makes of decoders powered via a Super Empire Builder from Digitrax. So far, so good.
I think a quality replacement motor should be the ticket for you, and of course a quality decoder is always an asset. Mate them sensibly so that nothing snags or melts or abrades due to heat or friction and you should have many good years with your 44 tonner.
-Crandell
I understand that in DCC, motors in engines are rapidly turned on and off to regulate speed. Is this hard on the motors? I remember the old days of "pulse power" and how we were cautioned to not use it exclusively since it tended to cause motors to overheat. I had a Spectrum 44 tonner (single motor) that "died" after some months of use, equipped with a Loksound decoder. I have replaced the motor and wonder if it will suffer the same fate.
TRNJ