Anyone know of an equivalent faster motor?

[madsci1016]

My Google-fu is weak today.

I'm trying to give SAGAR a speed boost. He is strong enough to pull himself over curbs that are taller then he is, but that's not needed. I'd rather have a lower gear ration for better speed. Does anyone know of an equivalent but faster motor to this one:

http://www.lynxmotion.com/Product.aspx?productID=653&CategoryID=11



Or a good source for similar gear head motors with encoder shafts?

[Razor Concepts]

Those look similar to the servocity gearmotors, they sell a 300rpm one as opposed to the lynxmotion 200rpm
http://servocity.com/html/3-12v_gear_motors.html

[madsci1016]

Good find, Thanks.

Although I still need them to have an encoder shaft off the back. hmmm....

Any others?

I'll sweeten the deal for anyone who finds me a suitable replacement, I'll send you two of the motors I replace in SAGAR. $40 value total. Same as pictured and linked, but no encoder shaft.

[MechHead]

I rarely ever see motors with shafts for encoders sticking out the back.  Unless you really need the precision you might be better off putting your encoders somewhere else in the system.
The closest motor I found was this:
http://www.ecrater.com/product.php?pid=6184108
It already has an encoder on it, but I have no idea if it is close enough to the motor you already have (I know the motor shaft is of a different diameter, and other specs.)
Personally, I would just over-volt the motor if the controller would take it.

[madsci1016]

This is for an outdoor AWD robot, I'd rather keep as much sensitive electronics inside the main chassis.

Motor looks interesting, I'll have to give it a good look.

[MechHead]

Well since it looks like the wheels are mounted directly on the motors I guess the encoder does need to be mounted directly on the motor.
Best of luck finding some motors that fit the bill.

[Invicta]

Hi

Have a look at these motors from Pololu, their specs suggest they will fit but there are no encoder shafts.

   http://www.pololu.com/catalog/product/1103
   http://www.pololu.com/catalog/product/1102

Notes.

Putting the encoder on the motor may not be wise because:
Unless you have tight linkage to the wheels of your robot you could get output from the encoder before your robot has moved.
Your MCU may spend all of it's time reading the output from the encoder and do nothing else.   

If you put an encoder on one of the wheels be careful of slippage. You need to accelerate your robot gently to avoid the wheels slipping and getting output from the encoders without the robot moving.

Let me know if I win the prize and I will send you my address.

Cheers

[Invicta]

Hi

Try this one:

   http://www.robotmarketplace.com/products/0-BHG31.html

Cheers

[madsci1016]

I'm quite aware of the pitfalls of encoders. The way I have it, I get 3000 clicks of the encoder per wheel rotation, the max wheel speed is over 2 revolutions a second, and I have an encoder on both Left and right side power tracks.

I have a dedicated Arduino that i built into a motor controller, all it does is count ticks and PWM an H-bridge, and with the way i wrote my code, it has time to run a 37 Hz PD controller around wheel speed, and measure battery voltage and current. Also, of course talk to the main MCU at 10 Hz. And it's only an 8 Mhz arduino.

So, yeah, I want my encoders to be on my motors to keep them protected inside the chassis, and they work fine doing so. And, with a lower gear ratio, it will actually be less work to count fewer encoder ticks for the same speed. Not to sound too defensive, but suggesting I get rid of my motor side encoders is not an option.

I'll look at these and see if I can remove there gear boxes and replace mine with them, as that seems to be the only option right now.

[tim_wang]

Hi,

I have used that exact same motor with US Digital's E4P encoder. It is a great combo! To gain higher speed for your robot, you have 3 options.

1) Use larger tires so you can travel farther per revolution. Not sure if changing wheel and tire dimensions is an option for you.

2) Overvolt the motor since the motor RPM is proportional to its input voltage. The drawback to this method is that you risk melting the rotor coil's insulation with higher running temperature and shortening the motor's life.

3) You can try transplanting the gearbox from this motor: http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=164786&productId=164786&cid=PDF%09CAT%09109. According to its spec sheet, the dimensions and holes are identical, so it should be a viable transplant.

Good luck!

[madsci1016]

Yeah, I have been thinking about the over-volt option.

Without building new battery packs, to series the ones I have would mean my battery bus would increase to 30V. Running 12V motors and 5V electronics (with regulators) at 30V bus just scares me, but i might try it.

Since my motorcontroller is closed loop around speed and my code won't be affected by battery voltage, I might just add a switch that series/parallels the two battery packs. So it can act as a 'turbo' switch during races.

[MechHead]

Don't overvolt the electronics, they will almost definitely fry.  Also overvolting the motor to 30V will make it get very hot and burn up rather quickly so I would not recommend overvolting unless you can go at a lower voltage, more like around 18V (or a little less).

[Razor Concepts]

He said he is using regulators    It is just that the voltage drop from 30v to 12v is significant and will waste a lot of power.

[madsci1016]

Using regulators for the 5V electronics, the idea here is to increase speed of the motors by increasing the voltage to them to 30V from 15V.

Also, all my electronics regulators are switching, so there would not be much more of a power loss then there is now.

[tim_wang]

I hope you have plenty of spare motors if you plan to run 12 volt motors at 30 volts. Over voltage increases the motor temperature and leads to insulation failure. The rule of thumb in electrical engineering is that the motor life is cut in half for EVERY 10 degrees Celsius increase in operating temperature.

[madsci1016]

I'm considering the over-volting option.

As anyone run with over-volt motors before?

Can I monitor motor case temperature to see if they are running too hot? Is it just heat to worry about, or is 28V really going to start arcing rotor windings? (Doesn't seem likely to me)

I was thinking of a single relay setup that would be able to parallel/series my two battery packs on the fly. So for straight a-ways, when (right now, all motors only draw ~200ma total at full speed) work load is low, series to 28V and monitor temps. When work load gets high (medium to hard turns draw jumps up to ~2 Amps total) parallel to 14V to keep the motor from heating up.

[MechHead]

I believe the only thing to worry about is the temperature.  I have run 12V motors at 24V before for short periods of time and that worked fine.

[madsci1016]

Man, Invicta was the closest. One click away from what he posted was this:

http://www.pololu.com/catalog/product/1442



500RPM with more torque then what i have. Max current will be an issue however.

Invicta I may owe you some motors, even though you were only close, not spot on. Maybe you pay shipping?

[Invicta]

Hi madsci1016

Glad to have been Helpful . I have sent you an email regarding your old motors. Good luck with your SAGAR.