# Is there a CV to make the motor only run at one speed?



## tkruger (Jan 18, 2009)

I have upgraded a DC motorized rotary snow plow to DCC. I used an NCE decoder. Is there a CV that I can set so that the power is off or 50%? Also can the decoder be set to only run it in forward regardless of the direction selected in the cab? I want to constant it with other locomotives but do not want the blade speed changing as they accelerate and de-accelerate. 

If nothing else I can just set the top speed low.


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## Brakeman Jake (Mar 8, 2009)

You want three features that I have never experimented,so...just ideas here...

Constant speed...use "speed table" and give CV67 through CV94 the same value,likey 128 for 50% throttle.
With these settings,you should have...Throttle 0=Off and throttle 1 & up=On

Constant direction...since there's no CV adjustments for motor direction that I know of,I'd try installing diodes (4,two opposing pairs) within the orange and grey wires so that the motor always gets the same polarity.Risky though,maybe the decoder won't like it,I can't tell....

Then if you want the blower to respond with the loco's commands,you'll have to give it the same address.Or use a separate throttle.


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## Brakeman Jake (Mar 8, 2009)

If you ever do it,I sure would like to know if it worked.....


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## tkruger (Jan 18, 2009)

Brakeman Jake said:


> Then if you want the blower to respond with the loco's commands,you'll have to give it the same address.Or use a separate throttle.


If I run it as a newer style constant all locomotives in the constant will respond to the lead locomotives number. This is why I want it to be on or off with the motor.


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## CTValleyRR (Jul 26, 2014)

Having a little trouble following. You keep saying "constant". Do you mean "consist"?


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## wvgca (Jan 21, 2013)

another option may be to set start speed fairly high [ie:30], and then set max speed just a bit higher [ie:32], on just the decoder for the blower rotor ..if it's in a consist, it would only come on when the main loco starts moving..


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## tkruger (Jan 18, 2009)

CTValleyRR said:


> Having a little trouble following. You keep saying "constant". Do you mean "consist"?


Sorry I meant consist.


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## Cycleops (Dec 6, 2014)

To do what you want to do you wont be able to run it in a consist, that would mean matching the speed with the other loco(s).


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## CTValleyRR (Jul 26, 2014)

tkruger said:


> Sorry I meant consist.


NOW things make sense!


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## tkruger (Jan 18, 2009)

Cycleops said:


> To do what you want to do you wont be able to run it in a consist, that would mean matching the speed with the other loco(s).


Ok, so there is no way to 'remap' the throttle to the voltage output values then. That is what i was hoping to do. 

I know I was able to match a pair of FA units to run identically by adjusting various CVs. Was just hopping for one more step.

Thanks all for the suggestions. Currently it works great with the variable speed blower. Now I need to build a tender to match it.


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## tkruger (Jan 18, 2009)

Found out how to do it. Thanks for all of the suggestions. They helped me allot. For the NCE decoder that I used I had to set the following 3 CVs to the same value, in my case 80 was the just right. CV2 is the start voltage, CV5 is the max voltage and CV6 is the mid voltage. Basically what happens is the curve of the voltage applied is adjusted based on these three parameters. Setting them all the same makes the starting, middle and end voltage applied to the motor the same at all throttle positions. In addition I can now add this to a consist. As soon as power is applied the decoder in the rotary translates every speed step to put out whatever the value of 80 is in volts to the motor. The locomotive's motors get whatever their decoders putout. 

Thanks all again for the help. So far the old Athearn blue box plow is motorized and converted to DCC. Next steps will be to add a tender (thinking of using a Mantua 12 wheel tender or something similar) with power pickups and LEDs for lights.


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## greenwizard88 (Dec 5, 2014)

You can use an h-bridge to keep the motor turning the plow in the same direction. Just attach the decoder leads to the "ac" input and the motor leads to the "dc" output.


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