Hi! So I’m working on a new project where I’d like to use all 6 motor ports in one program but during the first trials, my code seems to fizzle out after awhile as if the board runs out of power. I’m currently using a 9v wall plug and I found that if I plug it into the top power supply (straight into the Bricktronics shield) it will run longer than if I use the arduino mega board, but it still stops after awhile.
I guess my questions are, is it possible to use all 6 motor outputs at once? And would it be frowned upon to try plugging in another 9v into the mega (i.e. Will I break anything), or could I try using a 12v wall adapter?
Hello, good questions! You might be the first person to use all six motor outputs at the same time for an extended duration.
Don’t try to connect another 9v power supply. Power supplies don’t like to work together, and will actually fight each other if you try to do that. (This is because their desired output voltages will always be slightly off, like if one power supply wants to output 9.01 volts and another wants to output 8.99 volts, they will try to push the combined output voltage closer to each’s desired output voltage).
Always power a Bricktronics Megashield using the barrel jack on the shield, not the one on the Arduino Mega. There is only a single pin connecting the motor voltage between the two boards, and to prevent it from melting due to extreme over-current situations, we added a 200 mA auto-reset fuse there. That would explain why it stops working after a while when plugged into the arduino instead of the megashield. The fuse is not part of the power path between the megashield’s power socket and the motors, it’s only between the arduino mega and the megashield.
I would guess that either your chips are overheating and shutting down, or maybe your power supply isn’t able to provide enough current? What is the rating on your 9v wall plug? It should have a current rating in A (amps) or mA (mililamps, thousandths of an amp) on the case. Each motor can draw upwards of 0.8 amps (800 mA) [1] so you probably want a power supply that can handle at least 4.8 amps, to handle the worst-case power draw. Current used is proportional to how much load is on the motor shaft, so they will use less current when freely spinning (nothing connected) and use a lot of current when they are straining against a load that resists turning (moving heavy objects, etc).
Can you add some Serial.println statements to your Arduino code to check if the processor is still running when the motors stop? They the code is still running when the motors stop, then it’s probably an issue with the motor driver chips. Do they end up really hot when the motors cut-out?
If the arduino print statements stop printing out when the motors stop, that probably indicates a power supply problem. Double-check your 9v power supply to see how much current it can supply. If you have a multimeter we can make a slight modification to your power supply cable to be able to monitor how much current is being drawn from the power supply.
Good to know about where to plug in the power! And yes, the chips get super hot when it stops working so overheating sounds like a reasonable explanation.
My power supply that I’m using is 9V 2A. Is using a 12V power supply off the table? Also, could I put two power supplies in parallel to double the amperage?
I’m working on adding the series messages now and I’ll test it later tonight.
The only concern with using a 12v power supply is the motors, I don’t think they are officially rated to run at 12v but this page (http://www.philohome.com/motors/motorcomp.htm) shows some motor measurements done at 12v, so it just might work.
I think a better option would be to find a 9v power supply that can supply more amps of current. Ebay or amazon might be a good place to search.
I don’t think it would be a good idea to try to combine power supplies in parallel, I’ve heard that doesn’t really work very well, but you could try it and see if it works.
what does that first chip control? I quickly tried it with my original power supply and it seems the 1st motor port isn’t responsive now. Does that sound reasonable?
So, I have now begun my search to find a 9V and high Amp rating. Also, not to worry I do have another board
Oh no! At least you can see the cool inner-workings of the chip. That’s really weird that the chip overheated and popped, the L293D chips are supposed to be able to handle up to 36 volts. Maybe that was a defective or marginal chip?
That chip controls motor ports 1 and 2. The other two identical chips control motor ports 3/4 and 5/6.
If you feel like doing some soldering, we can totally send you a replacement chip. Otherwise we can swap out that board for a replacement. Get in contact with us and we’ll figure out what to do: https://www.wayneandlayne.com/contact/
Update! So good news, I had ordered a 9V 5A power supply online and it came in today. I tried it out with my friend’s shield and it works great with all 6 motors! The results are able to be replicated, which was an issue when using the other power supply since it overheated. Now, the board’s not even hot when using it. Thanks for all of your help and suggestions to help me solve this issue and thanks for sending me a replacement chip! I’m excited to fix my board and get this all squared away
