Large Scale Central

How to determine a car's direction of travel

Electronics
#21

Dan Pierce said:

A really simple way for determining direction would be to have an axle drive a small motor (a DC motor will be a generator) and the output would change polarity with a direction change. A small motor may have less drag than the wheel brushes. Now to have a double ended motor that car wheels can be mounted to to eliminate gears/drive belts.

You can even drive a led or a logic circuit with this method and no computer chip or relays needed!!!

Dan - That would surely work — I have some really small cell phone vibrator motors that might do the trick. The issue would be the physical connection from the axle to the motor - it sounds simple but could be a challenge - perhaps adding another wheel to the axle and use that to rub against the shaft of the motor.

I may experiment with that a bit…

thanks

dave

#22

Good news / bad news on the motor - I just hooked up a really small motor from a cell phone vibrator to a volt meter - it doesn’t reliably give a positive or negative swing till the shaft begins to rotate a what must be hundreds of revolutions per minute - at that point it puts out about 0.1 volts or -0.1 volts DC - that could be sensed by an op-amp.

At least with this small motor it would not be practical to sense direction at slow speeds - the reed switch and magnets determines the direction of travel at any speed so long as the wheel goes around a bit more than one time… perhaps a better solution for slow moving cars.

dave

#23

Dave, a 1.5 volt motor wont generate much power. Maybe a larger voltage motor would work better. I did an experiment years ago where I spun up a 12 volt motor, it would not charge a 9 volt battery, but it did ok charging a 6 volt battery pack.

#24

David - you are correct but such a motor would likely be way too large to use within a truck - I was going for tiny.

thanks

dave

#25

Dave, yea, maybe. But the hobby type 3 volt motors they used to sell at Radio Shack could possibly fit inside the truck, or be hung off the end of one.

#26

Dave, this is just a thought, it would require modification to every car in the train, however would add some realism to building the train.

What about just running a line off the motor control wires and MU it down the train? The benefit is that MANY passenger trains run with several hoses & cables between the cars. Even if its just an excursion train with air hoses, you could find some really cheap connectors online, and wire it on alternating sides, just like trainline hoses.

#27

That would certainly work, JD - I also considered using a small wireless transmitter in the loco to do the same thing - lots of options!

dave

#28

Dave, I just had a brainstorm/ “LightBulb”* moment. (*Its a minions thing, lol)

You were talking about those tiny cellphone vibrator motors. What about the motors that Aristocraft had used in their SD45 smoke generator? Those were a bit over 1/4" in diameter and maybe 5/8" in length. What I don’t know is what the voltage of model used was. They may have been stepped down from track speed.

If your customer isn’t afraid of a bit of kitbashing, one could modify a plastic wheel into a pulley, press it onto an axle between the steel wheels, and then use a rubber band to hoop that pulley to the smallest 12v motor you could find. The pulley would amplify the linear speed of the axle, giving you direction control at slower track speeds. But also, this is prototypically accurate until you get to the HEP age.

#29

Stick a 12 volt taillight blub from a car on the 12 volt line to give it something to do… that may bring it to life.

dave

#30

David Bodnar said:

Stick a 12 volt taillight blub from a car on the 12 volt line to give it something to do… that may bring it to life.

dave

oops - replied to the wrong thread!

dave

#31

J.D. Gallaway said:

Dave, I just had a brainstorm/ “LightBulb”* moment. (*Its a minions thing, lol)

You were talking about those tiny cellphone vibrator motors. What about the motors that Aristocraft had used in their SD45 smoke generator? Those were a bit over 1/4" in diameter and maybe 5/8" in length. What I don’t know is what the voltage of model used was. They may have been stepped down from track speed.

If your customer isn’t afraid of a bit of kitbashing, one could modify a plastic wheel into a pulley, press it onto an axle between the steel wheels, and then use a rubber band to hoop that pulley to the smallest 12v motor you could find. The pulley would amplify the linear speed of the axle, giving you direction control at slower track speeds. But also, this is prototypically accurate until you get to the HEP age.

JD - I may have one of those motors laying around - it is worth a try.

thanks!

dave