# SIMPLE speed control using batteries



## Jack - Freshwater Models (Feb 17, 2008)

OK, this is probably a long shot.

I want to build a critter and power it using a battery AND want to be able to control speed. I don't want to spend money on a comercially made speed controller. I have soldering ability and have made simple dc electric circuits and know the difference between a diode and a resistor. I don't mind buying some inexpensive electronic componants.

Is there a simple way to control speed (control voltage) between battery and motor?

Any help with this appreciated!

Jack


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## Del Tapparo (Jan 4, 2008)

Simple Critter Control

This will be smaller, more efficient, and easier to install and use than most anything you can do yourself. (But of course not near as much fun if you want to do it yourself







)


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## Michael Glavin (Jan 2, 2009)

Jack, 

Do you want to control the Critter mechanically i.e., when stopped turn a knob or what have you? There are commercially available mechanical speed controls for RC Cars with FWD-REV functions for $15.00 on up; plug-n-play. 

Michael


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## East Broad Top (Dec 29, 2007)

There's a simple circuit that uses a variable voltage regulator, potentometer, and a capacitor that will work. I built a series of those for my long-defunct HO scale railroad a while back. I forget where I saw the circuit diagram--I think Model Railroader?--but I found the backing for the variable voltage regulator that has what looks to be the same circuit but with different values for input voltage and potentiometers from what I used. Check Radio Shack for variable voltage regulators. (I think they still sell components.  ) 

I just gutted one of the old controls and put it in my B'mann Davenport. I discovered that the value of the potentiometer needs to vary based on the input voltage. When I run the control off of my 14 volt power supply, the throttle reaches top speed at the far end of the throw of the pot. When I run it on 7.4 volts (all that I need in the Davenport), I get top speed at about 1/2 way through the throw. 

The voltage regulator does require a good heat sink. I attached it directly to the die-cast frame of the Davenport. 

Later, 

K


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## Del Tapparo (Jan 4, 2008)

Linear voltage regulators are certainly an easy circuit and parts are easy to get. But that heatsink? ... That's where all of your wasted power from the batteries is going. It works. Just shortens your run times.

A PWM controller is much more efficient. My Simple Critter Control is good for a full 5 amps.I don't know the exact numbers, but the PWM controller is probably on the order of 98% efficient, while the linear regulator is around 50% (depending on speed and battery voltage).


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## East Broad Top (Dec 29, 2007)

Good point, Del. If you're knocking half your voltage off, you're wasting energy. (Matching your batteries to your normal maximum speed reduces wasted voltage, but if you're using it with a sound system, then you may have to match the voltage requirements of the sound system--and that could be twice your normal operating speed. Lots of wasted energy there. On the other hand, if you're looking for cheap-and-dirty throttle control, you're probably not putting a Phoenix sound system onboard. Check with your sound system's manufacturer to make sure it plays well with PWM when it comes to controlling things like chuff, motor revs, or other voltage-controlled sounds. Some do okay, some don't. 

Later, 

K


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## TonyWalsham (Jan 2, 2008)

There are plenty of speed controller kits available here in Australia from the likes of JayCar, Altronics and Dick Smith. 
I find it inconceivable that they cannot also be found from similar providers in any country. 
They will work. 
How well they will work is another question.


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## pdk (Jan 2, 2008)

Go here 

http://home.cogeco.ca/~daisybeach/index.html 

and choose 

Speed Control - For Manual Operation 

from the right hand menu


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## Stan Cedarleaf (Jan 2, 2008)

Jack, for many years I used simple battery voltage to set the speed of the trains. From 6 volt to 12 volt depending on the locomotive or kitbash I was running. I wired a DPDT reversing switch to be able to reverse the train if needed. The most common voltage was 7.2.


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## Del Tapparo (Jan 4, 2008)

Posted By pdk on 28 Jun 2010 07:11 AM 
Go here 

http://home.cogeco.ca/~daisybeach/index.html 

and choose 

Speed Control - For Manual Operation 

from the right hand menu 
The diode drop method also works, but the downside is still wasted power consumed by the diodes, and rather large speed steps between switch settings. Still better than the fixed speed of a battery though.


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## pdk (Jan 2, 2008)

Del's right about diodes being a primitive way to slow a motor, however, we're not talking about a huge waste of precious energy. I have never had a battery in any of my critters go from full to dead during an operating session -- that usually takes three or four sessions -- so, there's capacity to spare. Del's right about the steps between speeds too, but critters go real slow (in real life, anyway) so the steps (in my locos, at least) are not super jerky. In one of my critters I have no-step pot matched with a dpdt reversing switch and it is nice and smooth. But all I ever do it crank it from stop to full 90% of the time, so smoothness is a moot feature. 

Posted By pdk on 28 Jun 2010 07:11 AM Go here http://home.cogeco.ca/~daisybeach/index.html and choose Speed Control - For Manual Operation from the right hand menu The diode drop method also works, but the downside is still wasted power consumed by the diodes, and rather large speed steps between switch settings. Still better than the fixed speed of a battery though. 


Posted By Del Tapparo on 28 Jun 2010 09:22 AM


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## Torby (Jan 2, 2008)

In Junior College, I once made myself a motor speed "controler" with a 555, pot and big transistor. Worked quite nicely. Dad wanted a feedback system, but it worked beautifully for the purpose.


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## stanman (Jan 4, 2008)

And here I thought that adding and removing cars was the only way you battery guys controlled speed...


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## rmcintir (Apr 24, 2009)

Posted By stanman on 29 Jun 2010 09:10 AM 
And here I thought that adding and removing cars was the only way you battery guys controlled speed... 
Some of us even use Back EMF!


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## pdk (Jan 2, 2008)

I made one of those too! Mine had a big capacitor so that the loco started up real slow, like a homemade gokart with a slip clutch. Unfortunately it took the loco at least five feet to come to a panic stop, which led to some big crashes. Posted By Torby on 29 Jun 2010 07:22 AM 
In Junior College, I once made myself a motor speed "controler" with a 555, pot and big transistor. Worked quite nicely. Dad wanted a feedback system, but it worked beautifully for the purpose.


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## Torby (Jan 2, 2008)

The pot just changed the width of the pulse. Or did I keep the pulse width the same and vary the f. Junior college was a long time ago, but 555's are real easy to use.


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