Producing step and direction signals for 8 servo motors

Projects General Guidance
1

Hi,

I apologise in advance for being simple! I have a bit of a knowledge of pic and a couple of plcs but never a arduino.

I have an application where I need to control speed and position of 8 motors, they all need to run at exactly the same speed and position relative to each other needs to be maintained from startup.

I have selected the relevant dc servos and servo drives but I need to generate the step and direction signals to control them, direction is easy as I only need to run one direction I can simply tie the direction to Gnd or 5v, step frequency needs a range of 0.5-2 kHz approx.

I've looked a lot at stepper function libraries but they just seem a bit over complicated for what I need to do, I would like to be able to adjust the frequency with a potentiometer and read the frequency being produced on an lcd or similar.

So as far as I can see if I use a simple lcd shield and a potentiometer that should cover the control requirements but as far as the frequency goes is it not possible to connect the step wires two 8 digital outs and then the code (forgive my lack of proper terms) is basically pins 1-8 high, pause an increment read from a registry which the pot is read into and the pins 1-8 low, pause the increment and then loop?

Am I anywhere close or is there an easier way?
thanks in advance

Matt

2

The simplest solution would be controlling all motors from the same pins. Just hardwire them.

3

Hi,

Thanks,

Surely I will run into drawing too much current from one pin? What would be a simple opto isolator or transistor shield to cover this?

Matt

4

That would depend on the input impedance of the divers. A aduino pin can provide 40mA i believe. If you need exceeds this you have to take one of the measures you mention. or distribute the load between several pins set at the same time.

5

Hi,

Just been looking at an adafruit 16 channel servo / pwm i2c shield, is there any chance of making this work?.

Thanks

Matt

6

yes, but as i see it there is no need