We have been using an Arduino UNO with the Arduino Motor Shield Rev3 for several years with no problems. However, we just recently are having a problem in getting Motor Shield boards which actually work.
One batch of boards had obvious chip placement problems. Another batch has no obvious board problems but still will not allow the UNO to boot.
With the Motor Shield connected to the UNO (NO MOTORS CONNECTED), the UNO will not boot...it appears that the 5V (from USB or external 12V supply) drops considerably with the Motor Shield connected to the UNO Headers.
Again, this is with NO MOTORS CONNECTED...the screw terminals are completely empty.
My experience says that the Motor Shield should talk to the UNO and operate fine on just USB power. Obviously, actually driving a motor will require external Motor Shield power to supply the required motor current.
I have most any kind of test equipment that may be required. We think we have narrowed the problem down to the Vin PIN on the Motor Shield...once it is connected to the UNO, very high current is drawn immediately...thereby dropping the 5V needed to power the UNO board itself.
The Vin Connect has NOT been altered on the new boards. Again, this seems fine with no motor load actually applied.
Also, we are in the process of ringing out some of the components...comparing the non-working boards to the one working board we have in-house; however, since this problem has been seen on at least a dozen new boards, it seems unlikely that anything we find can easily be addressed.
UPDATE: The working board that we have has the Vin Connect CUT. However, this should not be a problem since there are no motors actually connected to the board. It's simply plugged into the headers on the UNO.
The Vin pin on the shield is intended to power the Arduino from the motor power supply. As such, it is not going to take more than 12V safely and you must cut it if the motor voltage is higher.
I would expect it to work un-cut with no motors but that is obviously not true for all motor shield designs.
I agree that it should work...the issue is that it DID work on the Arduino Motor Shield R3, now it doesn't on newer boards...which are still supposed to be Arduino Motor Shield R3.
Well one reason may be that the 298 can put out 4 amps. However, there is a new chopper that is rated @ 10 amps based on the ST Electronics STEP01 driver.
I'd look at the LMX358MMX and it's circuit components.
We are using the Arduino Motor Shield because it suits our needs, is readily available, and SOLD in the Arduino store. Switching shields will cause considerable issues for production and field support. So, yes, we will use the Arduino Motor Shield for as long as possible.
UPDATE: It appears that the boards ordered directly through the Arduino.cc store work correctly. This is frankly quite confusing as all that we have ordered through 3 different vendors seem to be manufactured through Arduino in Italy. Does anyone know of a BAD RUN of these boards?
Also, FYI, Arduino Store support has told me that the Motor Shield Rev3 is NOT DISCONTINUED regardless of rumors stating otherwise and we should feel confident in moving forward with this board for quite some time.
I compared the photo of my board to your photos, they look the same with regard to the IOREF line. They are different to the Eagle files provided by Arduino.
I contacted support@arduino.cc and my distributor (Distrelec), waiting for their response.
Yesterday, I was told by Arduino.cc Customer Support that there had at one time been a faulty batch of boards produced; however, he suggested that all of the defective boards have been returned and all available boards (at least through the Arduino.cc store???) should work correctly.
I had not gotten into looking at the Eagle files...perhaps you have found the cause of the problem.
Still hard to tell if we got counterfeit boards or not...anyone have any suggestions on this?
One day after your post I received an email from Arduino support with the same information.
And yesterday I got two other Motor shield boards: One that I ordered directly from the Arduino.cc store, and another one from distributor Distrelec as a replacement for the broken board.
The Arduino.cc board works fine, but Distrelec sent another broken board. Looks like they have faulty boards in their stock.
I compared the two boards, the PCB layout seems to be the same, the board color and silkscreen print look the same. So I think counterfeit can be ruled out. The only difference between the boards is the opamp IC4. The orientation of IC4 is different and also the device marking is different, it's "74TI R5R" on the Arduino.cc board and "K170 Y740" on the Distrelec board.
I emailed Distrelec and asked them to check their stock.
And I also emailed Arduino support again because the board's layout does not agree with the Eagle files they provide on their website. I asked if an updated schematics diagram is available.
Hi,
[soapbox]
I cannot believe they are still using the L298 dinosaur.
Arduino are trying to encourage new users, so a lot of the projects are battery powered, so why supply such an in-efficient controller.
There is stacks of space to change to a MOSFET version, and there does not have to be a software/library change, MADNESS. (I don't mean the band).
[/soapbox]
