Stepper motors in sound sensitive enviorment

I've been working on a project which will use stepper motors to power a calibration device. The device will move a microphone under different angles. Some sound will be sent, and the results from the microphone will be measured. The measurements will be preformed over a range of different positions.
So, the microphone will be moved (while this operation performed, ambient sound is of no issue), and then the microphone is locked in place, after which the measurement is performed (there must be virtually ZERO ambient noise).

The entire thing will use 6-medium sized stepper motors. These will be fitted with an encoder, some gearing and a controller. These are the components which I want to use:

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1,00x EvoDrive St-17 Controller [www.evarobotics.com]
5,00x EvoDrive St-23 Controller [www.evarobotics.com]
1,00x EvoDrive St-17 non-optical Encoder [www.evarobotics.com]
5,00x EvoDrive St-23 non-optical Encoder [www.evarobotics.com]
1,00x Gear Ratio 100:1 Planetary Gearbox Nema 17 Stepper Motor [www.omc-stepperonline.com]
5,00x Gear Ratio 4:1 Planetary Gearbox Nema 23 Geared Stepper Motor [www.omc-stepperonline.com]
1,00x SB485L - Basic USB to RS485 Converter [www.pimzos.com]

I don't have much experience driving stepper motors. I'm unsure whether or not these components will do the job. They are no doubt powerful enough, but will they meet my sound requirements ?

Thanks for helping!

Stepper motor with encoder = servo

Encoder ----- rotary or linear?

Get requirements straight, size, positioning, accuracy, load weight.
Put together a concept of operation.

What are positioning requirements? Accuracy X, Y, Z with in 50 micron.
Stage size 1m x 1m x1m? 10m x 10m x10m?

6 motors X, Y. Z Pitch, Roll, Yaw (you really need to Roll a microphone)
Pitch and Yaw will effect position of tip of sensor

What type of guide rails?
Consider motors with brakes -- so there is no hum from holding current to motors.

What will be driving this? Controller?

Position command (software)--> PC USB interface--> micro controller (Arduino) --> micro controller firmware--> stepper driver --> stepper pulses
read encoder --> encoder controller interface --> controller --> controller firmware --> feedback algorithm

RAMPS 1.4 will control 5 motors

You have a parts list before you have a design?

Good luck

The steppers will always hum when the drivers are active. So a brake on the axis and disabling the stepper drivers is mandatory.

A worm gear can also act as a break, when the gear ratio is high enough. ( Think windscreen wiper motors )
With encoders you actually wouldn't need steppers but before mentioned wiper motors would do.

20 years ago I've built a similar device for testing light bulbs/reflectors *sigh*
-Olaf

Thanks for replying.

I'm using a linear encoder Link.
These encoders working conjunction with this controller Link.

This is a digital encoder. It can be controlled via either RS232 or RS485. The end goal is to connect six of these to the RS485 bus.
The master of these motors will be a piece of custom software on a PC. The software will be written in c++, and in the end offer high level controls to control the robot. This software will be made into a library, and then ported to matlab so the thing can be controlled from matlab code.

This thing wont have a stage. Like I said, these motors will surely be powerful enough. Another engineer made a design and did the calculations. The motors must be able to reach a step angle of at least 0.5 degrees, which I can manage through the use of gearing.

I think the worm gear is a good idea. However I think I need to use brakes aswell, since not every motor will meet the size requirements when using worm gears.

Do you have any recommendations as to which brakes are good ? And do you know of small worm gears?
Also, are these any worm gear that don't make a turn like this:

I think its in the nature of a worm drive to be 90° angled.
I can't recommend a brake, since I don't know the weight of your setup.
Anyway it should be spring loaded with a solenoid actuator. A servo-controlled brake would have a humming servo, so NoGo..
-Olaf

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o_lampe
The steppers will always hum when the drivers are active. So a brake on the axis and disabling the stepper drivers is mandatory.

With correctly-chosen drivers and a well-regulator power supply, the only "hum" should be ultrasonic. The motors on my printer produce just a very faint hum when stationary, which I believe is caused by ripple on the power supply output. You can often reduce the motor current when the motors are not moving, which reduces any hum caused by ripple (as it does on my printer). So it may be possible to avoid the need for a brake by using a sufficiently well-regulated power supply and/or reducing motor current to the minimum needed when stationary.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Your link is rotary encoder

I know linear encoder as in
[en.wikipedia.org]

I still don't understand why SIX motors?

I still don't understand what maximum movements are necessary?

What type of drive? Belt, line, leadscrew?

I don't understand the need for encoder? Stepper motor with 3200 steps per rotation
can do repeatable positioning with great accuracy without encoder feedback.

You will have six RS232, RS485, USB interfaces to drive motors
six more RS232, RS485, USB interfaces for encoder feedback

$250 per driver
$72 per encoder

Insanity!!! You could get 12 smoothieboard controllers or 10 Rambo controllers
each could control 5 stepper motors and have a fast processor to do all the firmware duties.
and one USB or ethernet interface to worry about.

Simplicity is NOT a requirement?
This "Calibration device" sounds more like robot that will roam around looking for sounds?

Good luck!

Quote
smokeythebandit
Thanks for replying.

I'm using a linear encoder Link.
These encoders working conjunction with this controller Link.

This is a digital encoder. It can be controlled via either RS232 or RS485. The end goal is to connect six of these to the RS485 bus.
The master of these motors will be a piece of custom software on a PC. The software will be written in c++, and in the end offer high level controls to control the robot. This software will be made into a library, and then ported to matlab so the thing can be controlled from matlab code.

This thing wont have a stage. Like I said, these motors will surely be powerful enough. Another engineer made a design and did the calculations. The motors must be able to reach a step angle of at least 0.5 degrees, which I can manage through the use of gearing.