Motor Control Shield Cutting Out

Hi!

I am controlling a Nerf Vulcan with an Arduino and a motor shield. It is powered externally with 6 D batteries, supplying a total of about 9 volts. The gun works perfectly like this.

The issue is, I am trying to make it wall powered. I have three 9 volt AC-DC adapters wired in parallel. They each supply 210ma. The gun is supposed to draw about 600ma. The gun turns on and works perfectly when it is powered from the wall, until the gun tries to fire. As soon as that happens, the board resets.

If anyone can help me, I'd really appreciate it.

Thanks!

This is the shield: http://www.arduino.cc/en/Main/ArduinoMotorShieldR3

Could try putting a big capacitor (eg. 1000 uF) between the supply rail and ground of your Arduino board… making sure to get the polarity correct. Positive side on the supply rail, and negative side of the capacitor to ground.

Thank you so much! I tested it, and sure enough, when the motor turned on it was bringing it too low, resetting the board.

kornexls:
Thank you so much! I tested it, and sure enough, when the motor turned on it was bringing it too low, resetting the board.

Most welcome. I forgot to mention --- because you're wiring DC sources in a parallel kind of configuration, it might be a good idea to use blocking (protection) diodes on the outputs of each one, just in case. That's to avoid current from flowing back into any of those supplies. Maybe you're using blocking diodes already.

Ok, so I tested more, and although it's not resetting anymore, the motor is not turning with enough force to fire it. Does this mean the converters just aren't putting out enough current?

And thank you very much.

Does this mean the converters just aren't putting out enough current?

Yes. Motors briefly draw the stall current when they start up, and that can be several amperes.

As far as I know, the converters have no fuses/safety components in them, and I am not tripping the circuit breaker I am plugged in to. Given that this works when connected to battery power, what would be failing/tripping due to too much current?

Or do you mean that it's not providing enough current to start it? Is that even possible? It seems like it'd just start slowly if it was undercurrented.

kornexls:
Hi!

I am controlling a Nerf Vulcan with an Arduino and a motor shield. It is powered externally with 6 D batteries, supplying a total of about 9 volts. The gun works perfectly like this.

The issue is, I am trying to make it wall powered. I have three 9 volt AC-DC adapters wired in parallel. They each supply 210ma. The gun is supposed to draw about 600ma. The gun turns on and works perfectly when it is powered from the wall, until the gun tries to fire. As soon as that happens, the board resets.

If anyone can help me, I'd really appreciate it.

Thanks!

This is the shield: http://www.arduino.cc/en/Main/ArduinoMotorShieldR3

You never wire voltage supplies in parallel.

MarkT:
You never wire voltage supplies in parallel.

Why? What can happen if you do? And how is this different than putting batteries in parallel, which I know works.

Regulated voltage supplies can "fight" each other, because each one is set to a slightly different voltage.

Never wire them in parallel.

Thrift stores have great bargains on power supply bricks from laptops, monitors, etc. and the voltage/current output is stated on the label. Get one that can supply sufficient voltage and current for your project.

jremington:
Regulated voltage supplies can “fight” each other, because each one is set to a slightly different voltage.

Never wire them in parallel.

Thrift stores have great bargains on power supply bricks from laptops, monitors, etc. and the voltage/current output is stated on the label. Get one that can supply sufficient voltage and current for your project.

If they are identical power supplies, does that help? Or even then, will they mess each other up?

If you want your circuit to work you'll need a single power supply capable of enough current.

A voltage regulator is a high gain high current amplifier, it is not a battery, it is an active
circuit that will strive to output a precise output voltage. Put two in parallel and they can
fight, or simply one of them does nothing and is effectively useless because its set-point
output voltage is a few mV less than the other.

Batteries have internal resistance and are passive generators of voltage are will share
current if of identical type and manufacture.

Never connect (active) voltage sources in parallel.

Ok, I will buy a better converter.

Thank you all for the help!

:slight_smile:

Hi,
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom... :slight_smile: