OT reef help.. DC motors

andrew2010

andrew2010

New member
I need local help with a dc motor/ servo(continuos ) project. If anyone has any hobby/ robotics knowlege I will make it worth your time. Thanks in advance.
Drew
 
trying to make a piston type drive that is adjustable with a Pot or pwm circut. needs to be in a small footprint. an ardurino (sp) is to big. a 555 circut might work , however i just need a 0-50 rpm adjustment with the motor / servo.
 
this drive must be able to run 24/7 Back in the day if i remember right i could use a 5w 10k pot with a 3vdc motor but IDK if that would run to hot. Im trying to keep price low because I want to make multiple.s so a logic board would make this project not viable .
 
Are you trying to use a motor or a servo? There's a huge difference.

Do you need position feedback? Or do you just need something to spin at a set rate?

If you're concerned about heat, there are always heat sinks.
 
just an adjustable SLOW RPM that is durable and in a small footprint. piston gearing. (push pull) i thought a continuous servo but i would have to do a pwm. a 3v dc motor with a POT would be super simple , however I plan on having the entire mechanism in a water tight small project box, so the 3v dc motor idea would be ideal as far as simplicity but I worry about heat issues with the POT.

I dont need position feedback, the piston would be at a set length but speed of gearing/action must be adjustable.
BTW .. I do have a shaft seal for a 3v motor to keep project watertight if I go that route.
 
How much heat would the proposed motor generate at those speeds? I can't imagine it would be a whole lot.

I'd probably just do some testing prior to implementation, since it would be a rather simple test. Throw the motor in the box, attach a thermocouple to the motor chassis and set it to the maximum RPM you plan to run it at. Monitor for max temp.



edit: just noticed this was in a local subforum, and you requested local help....oops!
 
Are you trying to make a metering piston pump for dosage of small volumes of liquid on-the-cheap? If you don't want to get into the nitty-gritty of designing your own board, there are MANY off the shelf kits for DIY PWM solutions. Even cheap ones with simple analog trim pot control on the PWM board can be had for a handful of dollars. Frankly, almost so cheap it isn't cost-effective to design and build your own. If you need is as cheap of a PWM motor controller as you can find and a DC motor of appropriate size. Finding the motor will be the harder part. Mind your torque specs when you're doing continuous duty.

And yes, all are welcome here for that kind of help. I think the OP is hoping someone might be kind enough to drive to his house for the help :)
 
no.. no one has to drive to my house.. lol. I am not making a light mover or doser. It is something I have been tinkering with. pm to gary and gbru. and THANK YOU ! for the outside help.
 
simply put , the motor/ servo will be on continuous rotation at an adjusted speed. all of the heat I was worried about was in the POT not the motor. heat would be generated by high resistance in the pot to make the dc motor run at a low rpm
 
andrew2010 said:
simply put , the motor/ servo will be on continuous rotation at an adjusted speed. all of the heat I was worried about was in the POT not the motor. heat would be generated by high resistance in the pot to make the dc motor run at a low rpm
Click to expand...

How much current are we talking about?

mouser has pots rated up to 5 watts, you think you'll need something bigger than that?

Instead of using a pot to directly control the motor, why not use the pot to adjust a regulator? If you use a switching regulator (you can get "engineering samples" of switching regulators from TI for free), you won't have to worry about heat.

TI has switching regulator "boards" that are capable of handling up to 10A, and are pretty much plug and play.

I'm assuming you're talking about a gearmotor, not a standard high-rpm electric motor?
 
Last edited:
yes a 5 w 10k pot. thats big enough. @ CISCOKID same mechanical motion as a sterling but driven by a 3vdc motor.
 
Spinning that motor from 0-50 rpm probably isn't the best use of it. It would be much more desirable to spin at the nominal speed, or close to it, and gear down to the desired RPM.

I'm concerned about running into stall issues by reducing a (roughly)7k rpm motor down to less than 50 rpm.
 
I know it can be done, but i was looking for advice like that.. :) I was worried about reliability also . after further thought 20 rpm would be the slowest it should need to be.....so

-need it to be cheap ( or it will defeat my purpose)
-needs to be low voltage
-and very small footprint (small project box)

so i thought about a continuous rotation servo with a built in POT , however I dont know how to power one without a pc interface ,pwm , or arduino. If anyone knows how to simplify a power circut to a servo without one of the above that would be helpfull.
 
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