Motor shield and bluetooth module question
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Motor shield and bluetooth module question

by moimael on Thu Nov 15, 2012 3:57 pm

Hi,

We are currently on a project which uses an arduino mega 2560 rev 3 and adafruit motor shield.

We want to add bluetooth support with this module : https://dx.com/p/jy-mcu-arduino-bluetoo ... ule-104299

But it require to be wired to the VCC and GND pin of the arduino. (plus UART but they are freely accessible on the mega, even with the shield)

I wanted to know if the hole circled in red on the pictures are the same as the holes circles in blue and if i could solder some pin header to wire the bluetooth module ? Will the power be sufficient ?

Image

Other unrelated side question, is there a way (using a module or not) to power arduino + ext power on the shield with the same power supply ?

Thanks !
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Re: Motor shield and bluetooth module question

by adafruit_support_bill on Thu Nov 15, 2012 4:12 pm

Where did you purchase the shield?
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Re: Motor shield and bluetooth module question

by moimael on Thu Nov 15, 2012 4:24 pm

It's not exactly the same as the one of the photo don't worry ;) I take the picture from adafruit learning system. But the holes are placed the same way on the new one (i guess, i don't have the shield near to me at the moment)

I have the last revision with blue pcb. I bought it here : http://www.alpha-crucis.com/fr/shields/ ... 00817.html (again the picture is not up to date)
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Re: Motor shield and bluetooth module question

by adafruit_support_rick on Thu Nov 15, 2012 5:03 pm

The holes adjacent to the pins are wired together. You can see the traces on the solder side of the board. If the bluetooth module is designed to be powered from the arduino, then you shouldn't have a problem with power. To be safe, you should use an external supply for powering the motor shield.

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Re: Motor shield and bluetooth module question

by adafruit_support_bill on Thu Nov 15, 2012 5:16 pm

It's not exactly the same as the one of the photo don't worry ;) I take the picture from adafruit learning system.

Thanks for clarifying. It's been a couple of years since the new version came out. I didn't think any of our distributors had that much old stock on the shelves.

But anyhow, the two rows of holes are connected. Many people solder in headers to those holes for convenience.

Other unrelated side question, is there a way (using a module or not) to power arduino + ext power on the shield with the same power supply ?

That depends somewhat on your supply voltage:

If the supply is between 7 and 12v, you can use it to power both by connecting to the external power terminals and leaving the jumper in place.

If it is regulated 5v, you can connect to the external power terminals, remove the jumper and run a jumper from the positive power terminal direct to the 5v pin on the Arduino. :!: Be sure to get the polarity correct and be sure it is regulated 5v :!:

Other than that, separate supplies will be needed.
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Re: Motor shield and bluetooth module question

by moimael on Thu Nov 15, 2012 5:40 pm

Thanks you both ! It's much clearer now, i ordered some breakaway (from adafruit of course ! btw international air mail is very expensive for such a small thing, twice the price of the breakaway) to connect the bluetooth module solderless ;)

What is still unclear is the power supply for motor shield. I didn't know it should be regulated 5v. We bought a 12v 2250mAh power supply and made tests with it connected to arduino jack. The motor shield controlled only a 500mAh 10V stepper. From what i understood from the doc, it is bad to power motor shield + motors from the Arduino because it can harm it (we plan to add one more DC or stepper). So we were looking forward to plug this power supply directly to ext but you said it's a bad idea.

What is the best power supply configuration giving what i have ? (to drive 2 stepper or 1 stepper and 1 DC)

On a side note, did you plan to release a new version of motor shield with L298 instead of L293D ? I would be greatly interested in it !

Thanks for being so responsive and usefull !
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Re: Motor shield and bluetooth module question

by adafruit_support_bill on Fri Nov 16, 2012 7:13 am

What is still unclear is the power supply for motor shield. I didn't know it should be regulated 5v.

Your question was about using the same supply for both motors and Arduino. If you are using a 5v supply for both, it would need to be regulated.
From what i understood from the doc, it is bad to power motor shield + motors from the Arduino because it can harm it (we plan to add one more DC or stepper). So we were looking forward to plug this power supply directly to ext but you said it's a bad idea.

In general, we recommend separate supplies. But sometimes that is not practical. There are a lot of ways to make it work with one supply, but first we need to know what your motor requirements are.
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Re: Motor shield and bluetooth module question

by moimael on Sun Nov 18, 2012 8:38 am

We are doing a cocktail machine. Here is a video of early stage : https://www.youtube.com/watch?v=RJIllZ7x0-M.

So we control a 10V 500mA Stepper using Adafruit motor shield. We plan to add an electric actuator or DC motor to push optics for alcohol. It will most likely be 600mA. We also plan to control a pc fan (DC motor), 600mA too.

Now we power all of this with a 2250mAh power supply plugged on the arduino and jumper in place on motor shield. USB is plugged to program the arduino.

What is the best power configuration to suit our need ?

Thanks !
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Re: Motor shield and bluetooth module question

by adafruit_support_bill on Sun Nov 18, 2012 9:25 am

Stepper motors and PC fan motors (brushless DC) are not so noisy as brushed DC motors. They are also relatively steady loads, so you might be fine with those on the same supply.

Brushed DC motors very noisy electrically. When used as actuators, the current draw will spike on startups and direction reversals. When using a common supply, sometimes this is enough to cause erratic behavior or even a reset of the Arduino.

It sounds like your power supply has sufficient current capability to handle the peak loads. So noise would be the primary concern. One way to reduce the noise feeding back into the power supply is to add capacitors to the motor as described in the FAQ and shown in the picture below.

viewtopic.php?f=31&t=26873

Image
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