Electric motor recommendation

J

jensmith25

Senior Member
Hi all,

Can anyone recommend a tiny electric motor to run off a picaxe chip? It doesn't need to be able to carry any load as such. I'm building a plastic model kit of the Starship Enterprise from the 2009/2013 Star Trek movies and the on the warp nacelles, at the front there is a bussard collector on each nacelle.
Some people have used LED chaser effects but others have made a rotor template to match the design in the film and then backlit it which I think is a much better idea, but I don't know a lot about model motors, other than the ones I've used in technics lego many years ago.

There seems to be a bewildering number of motors available and I'm not sure where to start. One person has used a servo adapted to continuos rotation but I don't know if this is better than a small motor?

Requirements:
Low cost but reliable, if possible
Small and lightweight (has to fit inside a plastic nacelle without causing issues)
Only spinning a lightweight card or similar rotor so doesn't need to be powerful
Ability to run off the Picaxe chips


Any recommendations gratefully received.

Jennifer,
 
G

Goeytex

Senior Member
What RPM ?

When you say "run off the Picaxe ...", Do you mean directly from a Picaxe IO Pin, or can you use a transistor to take the load off of the Picaxe?
 
J

jensmith25

Senior Member
Goeytex said:
What RPM ?

When you say "run off the Picaxe ...", Do you mean directly from a Picaxe IO Pin, or can you use a transistor to take the load off of the Picaxe?
Click to expand...
Re RPM - I'm not looking for incredible speed I don't think. I think I would use a speed control on it so it can be slow when in impulse mode and then speed up before warp. I think the two rotors also need to rotate in opposite directions so one clockwise and one anticlockwise.

I would appreciate recommendations on best practise. I was considering the motor control board - AXE023 or the 18M2 High power board with the motor control CHI035.
I need to drive other LEDs for strobe effects etc, number not yet confirmed but I think something like the 18m2 is possibly a good option to do everything.
 
The bear

The bear

Senior Member
Hi Jen,
Another source, electric toothbrush motors. However, I think Jim & myself are talking recycling.
If its for a client, then I guess you are talking new.
 
J

jensmith25

Senior Member
The bear said:
Hi Jen,
Another source, electric toothbrush motors. However, I think Jim & myself are talking recycling.
If its for a client, then I guess you are talking new.
Click to expand...
Thanks Bear - yes, I need them to be new. This is an R&D piece so looking to sell as the end goal.
 
techElder

techElder

Well-known member
Also, in case you haven't gotten that far, the PICAXE program you build can be the "speed control" and IMHO should be. No need for all those "driver" dodads.
 
J

jensmith25

Senior Member
eclectic said:
Back to Goeytex's #2 post.

How fast? Numbers?

And how big? (maximum dimensions)

e
Click to expand...
I have managed to find another now discontinued kit that had motors and the speed was 120rpm. I am looking to control the speed to some degree using the picaxe programme so I can speed it up and down so there's a bit of leeway. A different suggestion is 58rpm @12v.


I will be working on the kit tomorrow so can get exact sizes then for the supplied kit parts. The kit is 1/500. A 1/350 model had a motor that was 12mm dia.
 
J

jensmith25

Senior Member
Thanks Erco. I've used standard servo's quite a lot so I know how they work.

I'll check sizes of the kit parts today and go from there.
 
J

jensmith25

Senior Member
Having started working on the model today the nacelles are actually pretty big. The bussard collector sits into this as a clear plastic dome and the rear piece of that has a 3mm dia shaft which I will need to drill out to fit a motor /servo shaft through depending on best options.

The width is 30mm.

Nacelle.jpg

I guess the main consideration is weight as they are made from very thin plastic so perhaps a continuous rotation servo is actually a better idea as I know there are very light, whereas the odd small motors I've used in the past have been quite heavy by comparison.

Whatever is in there will need some support so smaller is better.

Example of what they look like in the film model concept.
new-enterprise-final-03.jpg
 
erco

erco

Senior Member
If it's just for special effects, you might consider simply PWMing some LEDs in tubes, as I did here. No moving parts, decent effect.

 
J

jensmith25

Senior Member
Erco - Thanks. That is a route that others have taken, I was just concerned about the number of LEDs it will take and the output pins it'll need when there's other strobe effects to do too. There's two nacelles and they need to spin in opposite directions.

Maybe, I'm missing a simple way of doing it, but I assumed you'd need a PWM output for each LED or pair of LEDs (could hook up opposites I presume to get the alternate spin)?
 
R

Ravenous

Member
Coming in a bit late, but I've found some compact geared motors from:

https://www.precisionmicrodrives.com

(Ordering in the UK.) A bit over a tenner for a small DC motor with planetary gearbox built in. Should be possible to get around one rev per second. On my picaxe I drove these from ULN... series driver chips easily.

I have both the 10mm and 6mm diameter series. Only used to 10mm so far, they're easily enough to drive a very small robot with four AA cells. I think they should be able to rotate your filter/mask in a slow controlled manner...
 
J

jensmith25

Senior Member
Hi Ravenous - thanks very much. They are tiny and lightweight. Perhaps a bit more than I was thinking to spend but certainly fit the criteria and the 6mm is a bit cheaper - I could get 2 for £12 ish which would be ok. £20-24 for two might be a bit pricey depending on overall costs.

Thanks again,
 
erco

erco

Senior Member
jensmith25 said:
Erco - Thanks. That is a route that others have taken, I was just concerned about the number of LEDs it will take and the output pins it'll need when there's other strobe effects to do too. There's two nacelles and they need to spin in opposite directions.

Maybe, I'm missing a simple way of doing it, but I assumed you'd need a PWM output for each LED or pair of LEDs (could hook up opposites I presume to get the alternate spin)?
Click to expand...
Correct on all counts. My model had two nacelles like yours, but only half of each was visible, as shown in that video. And yes, I wired them in parallel to spin in opposite directions. More pins, and more work, but no motor noise and nothing to wear out. The apparent motion is smoother if you PWM each channel, but the effect is still good if you just switch them full on and off, especially as the number of channels increases.

It took some experimenting to get mostly even lighting inside the tubes. I used fat blue soda straws with a 10 MM white LED in one end. From the opposite end of the tube, I inserted a slim tapered piece of translucent wax paper to catch & spread the light around.
 
J

jensmith25

Senior Member
Thanks very much Erco. I have been concerned about motor noise but I think I perhaps have to try both methods and see which is best. Both have advantages and disadvantages.
 
erco

erco

Senior Member
These little metal gearmotors are cheap & quiet. http://www.ebay.com/itm/DC-6V-30RPM-3mm-Mini-Metal-Gear-Motor-Gearwheel-Shaft-Diameter-be6e-/400779327548 Haven't tested long-term durability, but your application sounds like light loads, so if you keep the exposed gears dust-free, they would probably last a good long time.

You probably don't need reverse, so you could PWM them with a single pin, and drive using a single cheap transistor (FET or even a classic TIP31) to control speed of two motors. That is, no H-bridge is required.
 
J

jensmith25

Senior Member
Thanks Erco - think I've found the same ones in the UK which is easier for me.

I doubt they will be on for very long at a time. Model lighting rarely is.
 
premelec

premelec

Senior Member
@erco - that's a nice looking little gear motor and I gather you have some in hand - could you give an estimate of reasonable working torque those gears would handle?
 
erco

erco

Senior Member
Can't say right now (they're offsite) but they are beautiful little metal gearboxes. They come in 6 and 12V flavors, I've seen 30-300 RPM: http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_sop=15&_nkw=mini+metal+gear+motor&rt=nc&LH_BIN=1

Starting at just $3, they are worth ordering a few IMO.

They use all metal gears, but no lube and open frame. I think if you enclosed them and put some light oil on they would handle a decent load for a while. FYI, they are often paired up with a small wheel on Ebay: http://www.ebay.com/itm/DC-6V-Mini-Metal-N20-Gear-Motor-with-12MM-Rubber-Wheel-For-Robotics-Car-/281915950868

And Pololu uses them on their 3Pi robot: https://www.pololu.com/product/975
 
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