Talk:Practical Electronics/Stepper Motors

What are the suggested diode values in the unipolar circuit? I am speaking of the bottom schematic.

Other type
This page seems to completely omit one of the most usual types of stepper motors, where several (4) coils are connected to common ground and the rotation is achieved by connecting them consequently. (At least 2 on the photo are of this type - I know it, because I have taken it ;) --Filip Dominec 07:32, 20 May 2007 (UTC)

Yes, "5-wire stepper motors" are pretty common. Now the page briefly mentions them under Unipolar as "Sometimes there are just five, as the centre taps may be joined internally." And the circuit shown is the standard one for 5-wire unipolar stepper motors (even though it shows the center taps joined externally). Is there anything else that needs to be said about 5-wire stepper motors? --DavidCary 06:01, 23 May 2007 (UTC)

MOSFETS
The IRF530/9530 and similar mosfets usually require more than 5v to *fully* turn on (I am not sure about the 530's tho). I am not an expert, but are you sure you don't need to transistor the gates of these using the motor supply? Looking in the datasheet the threshold voltage states 4v, but I am not sure if that fully saturates the gate. Furthermore, would the TTL outputs on the logic supply be fast enough supplying the needed gate charge to switch the mosfets fully without causes some heating. What I mean is, mosfets act like resistors when the mosfet is only partially on or off, we want the mosfets to go through this "resistive zone" as fast as possible.

Lastly, the mosfets turn off slower than they turn on, in the given schematic there is going to be a very momentary short in the supply during transitions (15ns of full short before the shorting mosfet starts turning off). Ok, if you arent doing PWM (chopper mode) like here, but it will generate significant heat if you do.