Powering stpper / shield

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mahuro
 
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Powering stpper / shield

Post by mahuro »

Hi All,

I hope you can help me ... I am not a bad programmer ... but a total newbie to electronics ....

I got a motor shield ...and a couple of stepper motors ( Nanotech ST4209S1006-B) , in the label (stepper) says 4.0V 0.95A ....

I Would like to power up my arduino from USB, and the Steppers from an external ( wall) source ... so my questions are:

1- what type of power supply do I need/can use ? I have one that says output 12VAC 1000mA ... would that work ... or can you suggest one ( I believe I read on the shield page that a 5-6 Volts is good, is that right ???

2- can i connnect the external power supply to the arduino DC jack with a power source greater than 5V ?? i.e.: the 12VAC , mentioned above ...

3- to Plug the power supply to the shield external , I would have to remove the "fitting" and plug the wires directly to each of the two screw inputs, how do I know which one is Live and which one is Neutral ?? I read that pluging it inverted will kill the shield ....

Many thanks !!

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adafruit_support_bill
 
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Re: Powering stpper / shield

Post by adafruit_support_bill »

1. 12v is too much for a 4v motor. 5-6v should work fine (there is about a 1.4v drop in the controller itself).
2. It is better to connect via the external power connection on the shield - and remove the jumper. This will give you better isolation.
3. If your power supply outputs are not marked, measure them with a meter to be sure.

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

Hi Me again ...

Just to add to the questions above: I just noticed that my steppers have 6 wires !! , how can I connect them to the motor shield ???

Cheers ..

Mahuro.

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adafruit_support_bill
 
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Re: Powering stpper / shield

Post by adafruit_support_bill »

Check here for tips for figuring out what the leads are: http://www.ladyada.net/make/mshield/resources.html
Once you find the two center-taps, twist them together and connect them to the GND (center) terminal of the motor output connector. Wire the other 4 wires as shown in the tutorial.

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

Hi ,

Thank you Arduwino ... I'll read and follow the tutorial and let you know how I get on ...

Cheers ...

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

Success !!!

Many thanks Arduwino !

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

It moves !!

Now that I have regained my composure .. in order for these steppers to actually do the job they need to move some quite heavy pieces the piece they are part of (between 5kg each)

I know the torque of these steppers is : Torque Max:15N-cm . I have searched the net for a clear explanation of calculating how much torque your stepper would need, but examples are quite vague.... Can you or anyone here point me to a good tutorial or explanation of what newtons / torque are and how to calculate them ( in a practical way ) ??

Many thanks.

Mahuro.

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adafruit_support_bill
 
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Re: Powering stpper / shield

Post by adafruit_support_bill »

Sounds like you need a good basic physics or mechanical engineering text. There are probably some good sites online as well, but I don't know of any firsthand.

The mass of the objects is part of the picture. You also need to know in what ways they must move, and how fast they must accelerate.

With a torque of 15N-cm, your motor will be able to just lift a load of about 1.5 Kg, using a 1cm long arm. I think it is safe to say that to deal with 5Kg loads you will need some sort of mechanical advantage (gears, pullys etc)

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

Thanks arduwino ... While I search for an answer can I run through a couple of ideas I got a bout this ????? ...

From you explanation that : With a torque of 15N-cm, your motor will be able to just lift a load of about 1.5 Kg, using a 1cm long arm

1- What happens if the Arm is doubled in size (2cm) does the torque decrease or increase ? , what is the proportion ? to a longer arm lesser weight to be handled, or viceversa.

2- If I needed a "bigger" steper, that problably would need a bigger power source (isn't it) but that would not affect the arduino board , as the board itself is being powered by usb ... If I needed a bigger stepper I could power it with 12V ( or whatever is required by the motor) or more to the Extrn jack, isn't ???

Many thanks.

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adafruit_support_bill
 
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Re: Powering stpper / shield

Post by adafruit_support_bill »

1- What happens if the Arm is doubled in size (2cm) does the torque decrease or increase ? , what is the proportion ? to a longer arm lesser weight to be handled, or viceversa.
The torque is constant. If you double the length of the arm, you halve the force that can be exerted at the end of it.
2- If I needed a "bigger" steper, that problably would need a bigger power source (isn't it) but that would not affect the arduino board , as the board itself is being powered by usb ... If I needed a bigger stepper I could power it with 12V ( or whatever is required by the motor) or more to the Extrn jack, isn't ???
You would use the external power connector on the motor shield (and be sure to remove the PWR jumper to separate it from the Arduino supply).
The standard shield can handle up to 36v at 0.6A. With some modifications you can increase the current capabilities a bit.

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

Many thanks Arduwino ...

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

HI Arduwino and all,

I have found that I need a bigger Stepper for my project the one I need is this one:

* STEPPER MOTOR, 0.9DEG, 2 PHASE
* Coil Type:Unipolar / Bipolar
* Torque Max:135N-cm
* Current Rating:1.1A
* No. of Phases:2
* Resistance:7.2ohm
* Inductance:16mH
* Rotor Inertia:480g-cm²
* External Length / Height:77.5mm
* Holding Torque:1.91N-m
* Indexing Angle:0.9°
* Output Current per Phase Max:1.1A
* Weight:1.0kg


Do you think I can power it up from the motor shield safely ????

Many thanks !!

Mahuro.

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adafruit_support_bill
 
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Re: Powering stpper / shield

Post by adafruit_support_bill »

1.1A per phase is about twice the capability of the L293D. But should be within the capabilities of a piggy-backed pair of L293Ds. Just line up the second one on top and in the same orientation as the first and solder each pin.

mahuro
 
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Re: Powering stpper / shield

Post by mahuro »

Hi arduwino,

Many thanks... I could not find a L293D , but I found this one from spark fun, which apparently is a " pin to pin replacement of the L293D:

http://www.sparkfun.com/commerce/produc ... cts_id=315

Description: Faster, cheaper, smaller, better, right? The SN754410 Quad Half H-Bridge is just that. Capable of driving high voltage motors using TTL 5V logic levels, the SN754410 can drive 4.5V up to 36V at 1A continuous output current! Please see datasheet for more information. This is a pin to pin compatible replacement for the L293D.

Many thanks.

Mahuro.

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adafruit_support_bill
 
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Re: Powering stpper / shield

Post by adafruit_support_bill »

Lady Ada has done a bit of research on these: http://www.ladyada.net/make/mshield/use.html
On using the SN754410: Some people use the SN754410 motor driver chip because it is pin-compatible, has output diodes and can provide 1A per motor, 2A peak. After careful reading of the datasheet and discussion with TI tech support and power engineers it appears that the output diodes were designed for ESD protection only and that using them as kickback-protection is a hack and not guaranteed for performance. For that reason the kit does not come with the SN754410 and instead uses the L293D with integrated kickback-protection diodes. If you're willing to risk it, and need the extra currrent, feel free to buy SN754410's and replace the provided chips.
That said, I've used the SN754410's in several prototypes without a problem. I've even piggybacked them to drive 2A/phase motors. For a critical application, I'd consider adding some external kickback diodes for better protection.

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