I have a project I'm working on and I need to run 4 brushed DC motors synchronously. Can anyone refer me to a motor driver that can do this and also power them? (Preferably taking up the least amount of pins possible- I also need to run an LCD on the same board) Thanks!
I need to run 4 brushed DC motors synchronously.
Since any two motors will run at different speeds when supplied the same voltage, you'll need some kind of [u]optical encoder[/u] to feed-back speed/position.
You'll need at least one pin per motor for on/off/speed. Another pin if you need to change direction, and one input-pin for the feedback.
Or if you don't need 360 degree rotation, you can use servo motors which have the driver & feedback built-in. And, you can run all 4 servos from the same pin.
FoxBlade:
run 4 brushed DC motors synchronously
I don't associate the word "synchronously" with DC motors.
A synchronous AC motor is one whose speed depends on the AC frequency. Hence several of them can run at exactly the same speed.
You could make stepper motors run synchronously by feeding them all with the same step instruction.
I wonder if you really meant to use the word synchronously?
Perhaps you just mean that you want to run 4 motors in parallel - but not necessarily at the exact same speed.
...R
Robin2:
I wonder if you really meant to use the word synchronously?[/quote
You're right. How about: Can anyone refer me to a motor driver that can let me supply the same amount of power to 4 motors and control it with an arduino so they run at a similar speed?
Do you need to control the speeds and/or directions of the motors? If not you could use the Arduino to operate relays or transistors to turn the motors on or off.
Suppliers such as Pololu sell motor drivers that can control two motors (I have some DRV8833 drivers) and you could easily use a pair of them for 4 motors. That sort of driver will allow you to use PWM to control the motor speed. Note, however, that the DRV8833 (as an example) requires a separate PWM pin for each direction if you want to be able to change direction and an Uno only has 6 PWM pins. An L298 driver can control direction with regular I/O pins and just needs 1 PWM pin per motor.
...R
Hi,
What is the application that you need this sort of control?
How close do the speeds need to be?
Thanks.. Tom... 
There is something in engineering called a DESIGN CRITERIA.
That would be the document that specifies the speed deviation tolerance for the 4 motors.
It would also be the document that answers the question "How close do the speeds need to match ?"
If you need precision, then you need tachometers and/or absolute encoders on the motor shafts.
I believe it is possible to add these features to motors that lack them by mounting them on the shaft but obviously it would be easier to buy motors that come with these features.