Potentiometer resistance

[Bryan Thatcher]

I have a 10 Amp (20V) power supply and I'm shopping for a potentiometer for an analog throttle. The maximum operating voltage of the pot is 100 VDC and my resistance options are 1k, 2k or 5k Ohms. I'm assuming the 1k option is fine for this application, but how would the 2k or 5k options affect the operation of the train? Thanks.

 

[Neil Robinson]

I have a 10 Amp (20V) power supply and I'm shopping for a potentiometer for an analog throttle. The maximum operating voltage of the pot is 100 VDC and my resistance options are 1k, 2k or 5k Ohms. I'm assuming the 1k option is fine for this application, but how would the 2k or 5k options affect the operation of the train? Thanks.

Please consider the power dissipation required.
Lets say you use a pot to reduce the voltage from 20V to 10V at full power (10A) The power dissipated will be the product of the voltage drop and current, i.e. 100W, and twice that if the track voltage is turned right down!
Often a low power potentiometer is used to feed the base of power transistor.to vary voltage.

 

[Deleted member 4232]

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[Bryan Thatcher]

Great, thanks for the suggestions and links, I'll look into them a little more later today. For reference, I was planning on planning on using these parts to create a multi train/track control center for my son.

https://www.ebay.com/itm/232407470780

https://www.ebay.com/itm/US-Stock-D...r-Voltmeter-/391701931217?hash=item5b334124d1

 

[Bryan Thatcher]

After a little research I have as many questions as answers. Could one of these units be used to slow start or stop an engine including when the direction is switched abruptly? Since they are not specifically for model railroads I may not know what I'm looking for. I opted against DCC for now until my son is a little older. Thank you.

 

[PhilP]

Have you considered battery RC for this?
No wires.. No track continuity problems.. No mains power anywhere in the running equation.. No large-current sources of power.. *OK, a shorted battery would count, but it can be protected, and would be enclosed.

 

[Deleted member 4232]

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[Deleted member 4232]

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[dunnyrail]

After a little research I have as many questions as answers. Could one of these units be used to slow start or stop an engine including when the direction is switched abruptly? Since they are not specifically for model railroads I may not know what I'm looking for. I opted against DCC for now until my son is a little older. Thank you.

As a rule a sharp reversal will set the train off in the opposite direction with the same current as before, potential damage can be caused to gears and motors with this treatment given on a regular basis.

With DCC and some Battery systems the train on a reversal of direction will slow down to a gradual stop and start in the opposite direction speeding up till the controller setting has been reached.

 

[Bryan Thatcher]

Bryan, here you go.
Alpha 100K Linear slide potentiometer
Slider knob for above.
DPDT Centre Off Switch

Case to house it in?
Remount LED on case?

View attachment 231428

DC Speed Controller board, picture below shows both types in use,
The smaller one:
Specification: Input voltage: DC6V - 28V Sustained current: 3A PWM duty cycle: 5% - 100% PWM frequency: 21KHz

And the one previously referred to:
Specification: Input voltage: DC12V - 36V Sustained current: 3A, Max. 6A PWM Duty Cycle:0 -100% PWM Frequency:500KHz

View attachment 231430

Just waiting for the cases then these can be assembled.

As for their sustainability and performance, two have been in permanent use for over three months, a third for the automatic shuttle was added for the Christmas Fair exhibition, all three were in operation for the two days, and they got hammered, by both young and old visitors, plus the operators gave the entire loco fleet a good workout!

Two more were assigned to the shop window display for automatic shuttles, this pair are about to enter their third week of 24/7 operation.

Meters, prefer these types, variety of AMP and Voltage levels available.

View attachment 231431

evilBay is useful and probably convenient for searching and tracking down the bits, there are other places to obtain the items.

I hadn't gotten as far as the case, but this is what I was envisioning. Do you sell this equipment or would you be willing to provide a parts list and supplier?

 

[Bryan Thatcher]

As a rule a sharp reversal will set the train off in the opposite direction with the same current as before, potential damage can be caused to gears and motors with this treatment given on a regular basis.

With DCC and some Battery systems the train on a reversal of direction will slow down to a gradual stop and start in the opposite direction speeding up till the controller setting has been reached.

Yes I've explained that to my son several times, I'm looking into preventative measures. I have several less expensive Playmobile engines and cars for him to use when I'm not around.

 

[Deleted member 4232]

Moved

 

[Greg Elmassian]

So, just double checking, your "analog throttle" means PWM is ok? (pulsed power)

Many people want "pure dc" which is not what you are getting here.

Most trains run fine on PWM, but some sound cards do not.

Greg