[Question] EV3 machine with 18 servo motors

[LegoDejc]

Hi fellas!

For some time now I am searching but don't find enough information anywhere...

I would like to build a machine with EV3 which will have 18 servo motors.

What components do I need to achieve it?

Please be as much specific as possible.

Any help would be much appreciated.

[DrJB]

The single EV3 brick can handle only 4 motors. Now, there were 3rd party contraptions that enabled you to multiplex multiple sensors in the past (not motors, primarily on RIS series). The most straightforward solution would be to use 5×EV3 and somehow have them all talk to each other ... not an easy feat, and you may need to upload a different OS than the stock version.

Edited December 11, 2014 by DrJB

[LegoDejc]

Thanks!

What about if I use NXTs?

They are cheaper to buy now.

If I remember correctly you can combine max 4 NXT bricks by bluetooth.

Is this true?

That would be 12 motors.

Remaining 6 - can I get them by connecting 3 NXT MMX multiplexers to one of four NXTs.

Does every multiplexer need it's own battery box?

[notareal]

What about this multiplexer? Sorry not tested personally, but sounds promising

http://www.mindsenso...age&PAGE_id=134

With this multiplexer, you can connect two additional motors to your NXT.

It also has a pass-through Digital Sensor Port to connect more sensors/multiplexers. (On this sensor port, you can daisy-chain more multiplexers to connect additional motors.)

• Connect NXT Motors and/or EV3 Motors
  
• Compact, Easy to Integrate Design
  
• Easy to Program
  
• Use with NXT and/or Arduino
  
• Supported in NXT-G, NXC, RobotC, LabVIEW
  
• Uses external power supply/battery for motors
  

• 
  

Edited December 11, 2014 by notareal

[LegoDejc]

Yes I was also thinking of this one.

[MajorAlvega]

Hi.

You need it pure LEGO?

You need original LEGO EV3 software?

And you need EV3/NXT servos or just servos (like Power Functions servos)?

If yes to the 3 questions, you need to connect 4 EV3 in daisy chain.

If not, I see several options, show you three:

a) just LEGO but PF servos are acceptable: use ev3dev and WeDo USB Hubs, each Hub can operate 2 PF servo motors

b) not just LEGO: beside the MUX you can use an I2C controller for normal (RC) servors, Mindsensor has one compatible with NXT/EV3 firmware but only allows 8 servos and I don't think you can use more than one but there are others, if you are confortable with some soldering you can use Adafruit 16 channel I2C PWM/Servo driver and control it with ev3dev.

c) not just LEGO: get 4 SBricks and a USB BT 4.0 dongle and use ev3dev to control 16 PF servos

Edited December 11, 2014 by MajorAlvega

[Surly]

If you get this almost lego part https://www.hitechnic.com/cgi-bin/commerce.cgi?preadd=action&key=NIL1046 you can run 4 servos from the EV3 and a further 8 PF servos.

Add this to the above solutions to get to 18.

Cheers

Surly

[NORAN]

So if you can do this without no LEGO servos you can use the PCA9685 from adafruit, heres a topic about it: http://www.eurobricks.com/forum/index.php?showtopic=102026&hl=