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### Topic: smd H Bridge (Read 2088 times)previous topic - next topic

#### SouthernAtHeart

##### Apr 30, 2012, 08:20 pm
I found a SMD H bridge and got a few, but now I'm not sure it will work.  I'm familiar with using the L293 H Bridge.  Does this one work the same way.  I'm wanting to control a 12 volt DC motor 200mA, with a 5 volt Arduino Pro Mini.
Which pins are the signal pins (connected to my pro mini) on this chip? Sa & Sb, or InA and InB.
Should Vdd be 5V from my Arduino, or 12V for the motor?

the chip is here:
http://www.vishay.com/docs/70007/si9986.pdf

#### Chagrin

#1
##### May 01, 2012, 08:02 am
Sa and Sb could be used for current or voltage feedback but if you're looking for the simplest implementation you'd just tie them to GND.

Setting InA or InB high gives you forward or reverse, setting both high gives you coast, setting both low gives you brake. Using PWM should give you varying levels of each.

VDD is your motor power but it also provides power for the chip logic.

#### SouthernAtHeart

#2
##### May 01, 2012, 09:55 pm

Sa and Sb could be used for current or voltage feedback but if you're looking for the simplest implementation you'd just tie them to GND.

Setting InA or InB high gives you forward or reverse, setting both high gives you coast, setting both low gives you brake. Using PWM should give you varying levels of each.

VDD is your motor power but it also provides power for the chip logic.

Thanks.  I'm not familiar with those feedback pins.  I won't need them, so with tie them to ground.
So, Vdd will be 12 volts, as my motor is 12 volts, but I won't need any logic level shifting to run the signal IN pins from a pro mini 5 volt?
The data sheet says,
Input Voltage High (VINH)    minimum is  2 volt, so I guess I could even use this with the 3.3V pro mini?

Thanks again!

#### Chagrin

#3
##### May 01, 2012, 10:44 pm
I believe you're correct on all accounts.

I wouldn't mind a second opinion from someone else in the forum, however.

#### SouthernAtHeart

#4
##### May 05, 2012, 08:46 pm
I usually use a pulldown resister on the enable pin to keep the Hbridge inactive while the Arduino is starting up, so the motor doesn't run...  This Si9986 chip doesn't have an enable pin.  Could I use 10K pull-down resisters on the signal lines (IN-A, IN-B) to keep them pulled low during power up?

#### Chagrin

#5
##### May 06, 2012, 08:39 am
Yeah that looks to be correct.

#### MarkT

#6
##### May 07, 2012, 06:30 pm
Yes, but 100k would be enough I think.  If you add 1k resistors in line with the inputs then if the motor driver blows it won't blow the Arduino as well - its a reasonable precaution when driving a high voltage (here 12V) chip from logic levels esp. during prototyping.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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