Adding potentiometer to lighting kit motors

bhatak · Post by **bhatak** » Wed Aug 07, 2013 5:26 pm

I am wondering if anyone has successfully added a potentiometer to the lighting kit for the polar lights 1/350 TOS Enterprise. I was hoping to be ale to slow the bussards down and just have the lights as a nightlight for my son.

Any advice for parts would be helpful.

lancehunter17 · Post by **lancehunter17** » Fri Sep 06, 2013 5:14 am

I plan on doing the same thing too! However I don't have the kit in hand but what you need to do is figure out how many ohms are in the bussard. My GUESS is 80 ohm should be . I also plan on putting a reverse switch to make them spin the other way. Their was a few times Kirk ordered full reverse!

lancehunter17 · Post by **lancehunter17** » Fri Sep 06, 2013 5:16 am

Hope that helps.

PatrikG73 · Post by **PatrikG73** » Sat Sep 21, 2013 10:29 am

Just remember that potentiometers usually don't support that many watts. Usually it's as low as 0.25W, which is not much if you have many LEDs.

Wattage is calculated as P = U x I, so if it's running on 12V, you can only draw 20mA from the source.

There are 2-5W resistors available, but they usually only run up to something like 33 ohms, which is not much, but you can try them.

Otherwise you can try to put in more resistors after each LED, or try to put a couple of the LEDs in series, like 2 or maybe 3, which are then parallel coupled to the power. I've done this in my own build of a Falcon, and it dimmed them pretty good. But remember that LEDs don't dim much before they just switch off.

Or if you're using a power adapter, try to get one with adjustable voltage and see if you can lower it. Just remember to get one that supports your needed power and amperes, or it will be very short lived.

Or (many choices...) just put some masking tape over them. Cheapest and safest way

MillenniumFalsehood · Post by **MillenniumFalsehood** » Mon Sep 23, 2013 2:21 pm

In his preview of the kit, ModelManTom added potentiometers to his motors and they worked just fine. In fact, it really added to the effect because they seemed to ramp up in power naturally when he twisted the knob.

swb186 · Post by **swb186** » Tue Sep 24, 2013 10:49 am

can anyone recommend a pot for this.

RossW · Post by **RossW** » Thu Sep 26, 2013 4:17 pm

AFAIK, pots are not recommended for adjusting DC motor speeds. You're better off using PWM from an Arduino/PIC but I realize that is more difficult and costs money. There might be some pre-built motor controllers available, though.

http://www.electro-tech-online.com/thre ... tor.96709/

"You can't use a potentiometer by itself to control the speed of a motor. It has to do with ohm's law and how potentiometers are constructed. First off, the motor needs x voltage to run and will draw y current. In most cases the current needed will exceed the current handling capability of the pot therefore burning it out. Secondly, the most commonly found potentiometers are "audio" taper potentiometers and not "linear" taper, therefore the resistance change across them is "bunched up" to one end.

While you might be able to setup a transistor and a potentiometer to change the speed of the motor you are going to burn the transistor out in most cases because once again of current requirements of the motor."

You can also create adjustable PWM using a 555 timer

http://www.eleinmec.com/article.asp?28

or this one (which uses only 1 555):

http://www.electro-tech-online.com/thre ... ost-779858