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Topic: Motor Shield Capable of Driving 5 DC motors? (Read 1 time) previous topic - next topic

Jeffro


If you use H-Bridge ICs, they may already have flyback diodes installed. If they do not, they are a smart thing to add. Other than that, the IC really doesn't typically need anything extra. For my TA7291S chips for example, you have IN1 and IN2 which control forward or reverse, and you have OUT1 and OUT2 which you wire up to your motors. These also have the flyback diodes built in. Look at the datasheet for a "typical application circuit." I attached it.

The S comes in a really compact SIP package which I find nice to work with. You would need one for each motor. The L298 ICs are quite different, but they do have two H-bridges in them, so you can control 2 motors with one IC.

However, since these cannot handle 6A directly, point me to some of the ones you found and I might be able to give you a hand with putting the circuit together.


Hi RetroPlayer,

Thanks again. I found http://www.ti.com/lit/ds/symlink/lmd18200.pdf this H-Bridge. I did see on the datasheet that it has a built in protection diode. It looks like it can handle the amount of current & voltage that is required. It has a continuous output current of 3.0A with a peak output current of 6A. Since the motors have a max peak stall of 5.54A, I figure this will be suitable. Although these would be $75 for five,  I'm willing to drop the money if this is my only option. Would I be able to just buy these with no extra circuitry/design and connect them to the arduino & motors?

Retroplayer

It looks like you would only need a few common components to get that H-Bridge running. The examples show a PWM chip being used, but if you will be using the PWM from the arudion, you don't need that. The bootstrap caps are necessary. Depending on whether you wish to use the current sense output, it looks like you may need a few more common components.

I have learned one thing from looking around at these.... I am in the wrong business. Good Lord on these prices. Ridiculous!

Jeffro


It looks like you would only need a few common components to get that H-Bridge running. The examples show a PWM chip being used, but if you will be using the PWM from the arudion, you don't need that. The bootstrap caps are necessary. Depending on whether you wish to use the current sense output, it looks like you may need a few more common components.

I have learned one thing from looking around at these.... I am in the wrong business. Good Lord on these prices. Ridiculous!


Ha! No kidding on the prices! I can get the bootstrap caps and necessary resistors (for the current sense output) from one of the labs at the university. Another question though, what is the current sensing actually there for? I read on the datasheet that the LMD18200 uses sinking and sourcing outputs. Does the statement (below) from the datasheet just mean that the current sensing pin is used for sourcing? I guess what I'm really trying to ask is why is pin 8 there and what purpose does it serve?

"USING THE CURRENT SENSE OUTPUT
The CURRENT SENSE output (pin 8) has a sensitivity of 377 mA per ampere of output current. For optimal accuracy and linearity of this signal, the value of voltage generating resistor between pin 8 and ground should be chosen to limit the maximum voltage developed at pin 8 to 5V, or less. The maximum voltage compliance is 12V. It should be noted that the recirculating currents (free
wheeling currents) are ignored by the current sense circuitry. Therefore, only the currents in the upper sourcing outputs are sensed."

wildbill

Guessing - I haven't used one, but I'd assume that the current sensing pin gives you the opportunity to measure the current the motor is pulling, on the arduino by using analogread and doing a little math. This would let you detect when your motors are stalled.

Retroplayer


Guessing - I haven't used one, but I'd assume that the current sensing pin gives you the opportunity to measure the current the motor is pulling, on the arduino by using analogread and doing a little math. This would let you detect when your motors are stalled.


Yes, that is typically what it is used for. It is also used for torque feedback, which some applications require.

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