motorpwmstepper motorvoltage
I'm using a PWM control signal that ranges from 0-24V to drive a stepper motor. However, the datasheet in the driver says it should range 0-5V.
How can I bring down the amplitude of my PWM control signal? Would I use a 5V regulator or does a potentiometer make more sense? If neither of these, then what?
I'm not sure what you mean by 'the limit setting potentiometer', but (assuming that you mean the current sense resistors \$R_{S1}\$ and \$R_{S2}\$ (which would be an interesting design, those should be matched low-impedance resistors) I read on page 9, in the section Internal PWM Current Control:
The maximum value of current limiting is set by the selection of RSx and the voltage at the VREF pin. The transconductance function is approximated by the maximum value of current limiting, \$I_{TripMAX}\$ (A), which is set by
\$ I_{TripMAX} = V_{REF} / ( 8 R_S) \$
where \$R_S\$ is the resistance of the sense resistor (Ω) and V_{REF} is the input voltage on the REF pin (V).
Do you have access to the REF pin (pin 17)? If so, adjusting this with a DAC will produce the same effect as varying the sense resistors.
If not, the Enable input is probably a better choice than cutting the power or using the sleep or shut-down pins, those would incur a 1 ms delay (per the description on p. 10).
Page 208 shows the block diagram of a typical I/O port.
The PWM peripheral communicates with the output drivers via the output multiplexers. Therefore the sink/source capabilities in PWM mode are the same as when they're in GPIO mode, which for this device is either 15mA or 20mA.
You may need to use an external driver fed from the PWM signal if you need strong sinking and sourcing capabilities.
Best Answer
Not the voltage regulator. That will try to give a constant voltage at the output, but PWM at the input won't allow this. Anyway, the regulator won't work, but your PWM signal will be lost.
A potentiometer will work, and allow you to vary the output level, but if you know what level you want (5V) then a resistor divider is cheaper. 3k9 for the higher resistor, and 1k for the lower one will give you 4.9V. Both values are E12, so they are more common that the values Nick suggests.
edit
Nick suggests higher resistance values, like 39k and 10k. Lower values mean less susceptibility to noise and other disturbances, and if you're working with stepper motors you can afford the extra few millis; the stepper motor will consume a lot more.