DMU lights on Analogue control

Basic electrical and electronics, such as DC/Analog control.
Someone
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DMU lights on Analogue control

Postby Someone » Thu Dec 30, 2021 8:51 am

My friend has a DC layout and just bought a Class 153 by Hornby, he wants to keep the lights on while the train is stopped at a station, but in DC obviously is quite difficult, my friend applies just enough power to the track the keep the lights on but not move the motor this works well but he is worried it's bad for the Motor. Is there anyway to keep the lights on while DC without ruining the motor is my friends previous method safe.
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Re: DMU lights on Analogue control

Postby Flashbang » Thu Dec 30, 2021 9:22 am

Simplest would IMO be to rewire the lights to run on battery power and add a simple On/Off switch somewhere convenient. This does of course mean replacing the batteries regularly though!
Next and a very similar approach, would be to use a charging circuit and rechargeable battery. The DC track power, when applied, charges the battery. Polarity and suitable circuitry for charging is needed.
Then comes high frequency lighting using the rails, but this should not be used with any decoder (DCC) fitted loco.
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Re: DMU lights on Analogue control

Postby Suzie » Thu Dec 30, 2021 9:41 am

There are a couple of answers to this, but basically if there is not enough current flowing to move the motor then there is nothing to worry about, you are not going to damage the motor.

If he just has the 153 it will not be a big spend to buy an inexpensive DCC system (Bachmann E-Z Command can often be had quite cheaply second hand for around £30 when split from a train set) and a Zimo decoder (£20), and he will not have to worry.

If he just has a simple DC controller then another alternative is to cut one of the motor links (the link between the end pins at either end) on the decoder blanking plug and put in a couple of inverse series 3.6V 1.3W Zener diodes instead, this will prevent the motor drawing any current at low controller settings.

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Re: DMU lights on Analogue control

Postby Someone » Thu Dec 30, 2021 10:07 am

Suzie wrote:There are a couple of answers to this, but basically if there is not enough current flowing to move the motor then there is nothing to worry about, you are not going to damage the motor.

If he just has the 153 it will not be a big spend to buy an inexpensive DCC system (Bachmann E-Z Command can often be had quite cheaply second hand for around £30 when split from a train set) and a Zimo decoder (£20), and he will not have to worry.

If he just has a simple DC controller then another alternative is to cut one of the motor links (the link between the end pins at either end) on the decoder blanking plug and put in a couple of inverse series 3.6V 1.3W Zener diodes instead, this will prevent the motor drawing any current at low controller settings.

He simply just turns the Knob down enough to stop the motor moving but enough to keep the light's on.
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Re: DMU lights on Analogue control

Postby Someone » Sat Jan 01, 2022 8:08 am

Suzie wrote:There are a couple of answers to this, but basically if there is not enough current flowing to move the motor then there is nothing to worry about, you are not going to damage the motor.

If he just has the 153 it will not be a big spend to buy an inexpensive DCC system (Bachmann E-Z Command can often be had quite cheaply second hand for around £30 when split from a train set) and a Zimo decoder (£20), and he will not have to worry.

If he just has a simple DC controller then another alternative is to cut one of the motor links (the link between the end pins at either end) on the decoder blanking plug and put in a couple of inverse series 3.6V 1.3W Zener diodes instead, this will prevent the motor drawing any current at low controller settings.

Also I forgot to mention his controller is PWM.
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Re: DMU lights on Analogue control

Postby Bigmet » Sat Jan 01, 2022 12:30 pm

Someone wrote:..,controller is PWM.

Which neatly explains how the effect is achieved. A good PWM design set for small output can deliver very brief pulses of power, insufficient to overcome the friction and inertia of the motor and drive line to make the motor turn, but which electronic devices such as LED's will operate on. (You might even get a sound effect of rattling from the motor.)

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Re: DMU lights on Analogue control

Postby Bufferstop » Sat Jan 01, 2022 2:06 pm

Powering a train with PWM sufficiently to put on lights and make the motor rattle is a No-No. It's akin to leaving a DC loco on energised DCC track. There if there's not enough voltage to make the motor turn, it's not going to generate a back EMF. This means Ohm's Law applies using the supplied voltage and the measured resistance. Normally the back EMF is deducted from the supplied voltage which significantly reduces the current which will flow. It mightn't be enough to turn the motor but it can be enough to make the coils uncomfortably hot. Leave it there long enough the windings loose their insulation and the coils short out.
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Re: DMU lights on Analogue control

Postby Someone » Sun Jan 02, 2022 6:49 am

Bufferstop wrote:Powering a train with PWM sufficiently to put on lights and make the motor rattle is a No-No. It's akin to leaving a DC loco on energised DCC track. There if there's not enough voltage to make the motor turn, it's not going to generate a back EMF. This means Ohm's Law applies using the supplied voltage and the measured resistance. Normally the back EMF is deducted from the supplied voltage which significantly reduces the current which will flow. It mightn't be enough to turn the motor but it can be enough to make the coils uncomfortably hot. Leave it there long enough the windings loose their insulation and the coils short out.

He only leaves it for 10 seconds in a station, when he stops the train in a yard or siding he stops it completely.
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