I have a recently purchased Ardumoto shield. (Version unknown – not on board)
Everything works great (once I got the newer sketch to match the board).
I want to drive the motors at the max voltage that the board allows but I want to keep the Arduino running at 5V.
How do we separate the motor voltage from the logic voltage?
dkirtley,
It appears from the [catalog page that the Ardumoto power comes from the Vin pin of the Arduino. That pin, IIRC, is the voltage being fed to the Arduino through the power jack, it is not the logic voltage. In theory, you’re permitted a relatively high Vin for an Arduino, but above 12 V it’s likely to start overheating its regulator. How high are you looking to go?
Furthermore, the Ardumoto is shown without pins. There are comments on the catalog page referring to other means of attaching to Vin. There are two holes in the Ardumoto board labelled “Vin: Max 18 V”.
If you want to isolate the Vin for the motors from the Vin for the Arduino, I’d omit the Vin pin from the Ardumoto and connect the motor power supply to the Ardumoto Vin terminals. The grounds for the Arduino, Ardumoto, motor power supply and logic power supply, however, should all be connected to each other. To do that, I’d use the pin intended to tie the Ardumoto ground to the Arduino ground, and tie motor power supply ground to it.
Note: It appears that the intention was that you provide power to the Ardumoto and that power is then provided (through the Vin pin) to the Arduino. If you omit that pin, you’ll need some other way to power the Arduino.
Have Fun,
Eric ](http://www.sparkfun.com/commerce/product_info.php?products_id=9815)
Well, I would really like to go way beyond what the Ardumoto can handle (Ideally, I would love to push 48V through it since the L298 can deal with it. 
) but for now I would like to go to the 18V max. I connected the motor at 12V and was surprised when it lit up the Arduino. Sure am glad the Arduino is so forgiving.
Here is the full story:
I am playing with a little Emco CNC lathe that has lost its controller.
I am currently driving the spindle at 12V for testing but that is too high voltage for the EasySteppers and I have to run them separately. If I can separate the motor voltage from the logic voltage, I can run the motor higher and still have everything else at 5V for the steppers.
dkirtley:
Well, I would really like to go way beyond what the Ardumoto can handle (Ideally, I would love to push 48V through it since the L298 can deal with it.
It may be that the “Max. 18 V” is there to protect the Arduino, but you’ll need to examine what else is on the Ardumoto to make sure. If the Ardumoto (all of it, not just the L298) can handle the higher voltage, you may be able to run it at higher voltage as long as you remove the “Vin” pin connecting Ardumoto and Arduino power circuits
dkirtley:
Here is the full story:I am playing with a little Emco CNC lathe that has lost its controller.
I am currently driving the spindle at 12V for testing but that is too high voltage for the EasySteppers and I have to run them separately. If I can separate the motor voltage from the logic voltage, I can run the motor higher and still have everything else at 5V for the steppers.
To what (which circuit/pin on which board) are you referring as “logic voltage”?
How is the input voltage of the Ardumoto connected to the EasySteppers? More generally, how are the EasySteppers connected to anything else in this system.
Tangentially: If you’re driving only one motor with the Ardumoto and you have in hand the parts that are described in the [posted instructions, I suggest you take a look to see if you can use the terminal block provided for the second motor as a means of connecting the motor power supply to the Ardumoto. (Yes, you will need to unsolder it and you may need to unsolder both terminal blocks so you can separate them.)
Eric](http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=183)
The Ardumoto has a separate voltage in for the motors and is also connected to Vin and 5V on the Arduino and a soldered connection on board from 5V to V-Logic on PCB. In general, all the power on the board is all tied together in the same circuit as shipped. With only the motor voltage input connected to 12V, the circuit also feeds power back to the Arduino board at 12V. I was somewhat surprised by this when I connected it at first getting ready to test. Luckily, I had not connected any power to the Arduino prior since I usually power it off USB.
The logical choices would be to disconnect one or some combination of: the soldered V Logic connection, the 5V, or the Vin on the Ardumoto PCB to isolate the motor voltage from the logic control and the Arduino. I figured I would take my time and ask if someone already knew which to disconnect instead of trial and error and magic smoke releases.
The main limitations that keeps the Ardumoto from taking more than 18V would be the diodes, the capacitor, the traces on the board and the driver chip not having a heat sink. In other words, the only parts that can take more power are the connectors and the L298. Not a fault of the board. It was never designed to drive motors as large as I intend. Eventually, I know I will have to build my own controller but I am not quite there yet.
I have another L298 on a breadboard and some Schottky diodes rated for up to 100V to build a replacement but I am still looking at whether that will be enough to drive the motor I am dealing with. It is nearly 10 years old and lacking documentation. I honestly would rather dump the motor and move to something more modern with more power but I am not really ready to do major surgery on it as the lathe is pretty much built around it. If I am up to the 45V it is designed for, it carries low enough amperage to use the L298. At 12V, I don’t know. It might be pushing it. The L298 on the Ardumoto was getting pretty hot running it at 12V but it has no heat sink.
dkirtley:
The Ardumoto has a separate voltage in for the motors and is also connected to Vin and 5V on the Arduino and a soldered connection on board from 5V to V-Logic on PCB.In general, all the power on the board is all tied together in the same circuit as shipped. With only the motor voltage input connected to 12V, the circuit also feeds power back to the Arduino board at 12V.
It appears to me, from the [schematic, that power enters the system through the Vin connection on the Ardumoto near the motor connectors, then passes down through the “Vin” pin to the Arduino. The Arduino’s regulator produces 5 V from that and supplies it, through the “5V” pin to the logic on the Ardumoto.
dkirtley:
The logical choices would be to disconnect one or some combination of: the soldered V Logic connection, the 5V, or the Vin on the Ardumoto PCB to isolate the motor voltage from the logic control and the Arduino. I figured I would take my time and ask if someone already knew which to disconnect instead of trial and error and magic smoke releases.
I’m a bit confused, as I thought I answered this question in my first posting in this thread. If you remove the “Vin” pin from the Ardumoto board, then the Arduino will not be fed the motor voltage. If you don’t want to cut the pin, you could try bending it so it fails to connect with the Arduino. Alternatively, you could de-solder that group of pins and replace the pins you need (appear to be 5V and GND) with individual pins.
I do not believe that removing the “5V” pin or the solder jumper would isolate the Arduino from the power fed to the Ardumoto. Removing the “5V” pin or the solder jumper would, it appears, deprive the Ardumoto of the logic power it needs.
You will need to provide some other power source to the Arduino. The USB connection should work, as should providing 7 to 9 V through the Arduino’s power jack.
If you leave the “5V” pin intact, the Arduino’s regulator should continue to provide the logic power for the Ardumoto.
If you’re feeling adventurous and want a single-power-supply configuration, it appears you could (instead of what I’ve suggested above):
I hope that’s a more helpful response,
Eric](http://www.sparkfun.com/commerce/product_info.php?products_id=527)](http://www.sparkfun.com/datasheets/DevTools/Arduino/Ardumoto_v13.pdf)
Eric,
No, you are being very clear and helpful. It is just me being somewhat unable to explain myself clearly. I am just a bit frustrated with lack of flexibility with the design choice the board designer made. Yes, I could leave off the Vin pin. Then I have a shield that I will be unable to stack at a later date which is unacceptable. What they really should have done is to provide a jumper to be able to select motor power input from Arduino compatible motor voltage or a separate motor voltage source. I guess what I will do is to cut the trace and install one myself. I just hate making permanent changes to the board because I am not planning on permanently dedicating this board to this application. It is just proof of concept at this point because the board really is not designed to handle the full power requirements for this application. It is not my personal lathe and if they want a permanent one, the owner can buy one for themselves. 
Hi,
I am using ardumoto and arduino uno, supplying power to arduino through USB and 12 volt to ardumoto though Vin pin of shield saperately, i have removed the Vin pin which is feeding power to the shield.
I set the pwm value to 80 when i tested the code saperately on motor it was working but as i attached the motor to my robot it was unable to bear the load and was not able to move, and now my arduino is not getting detected! It’s just not showing up in the serial port, I have tried dmesg and it’s not getting detected, though it’s power led is glowing and there are no signs of anything burnt!
Can anyone give me the reason what has happened to my arduino - bootloader burned out or some issues with all the grounds?
Thanks