gogo2520 Posted April 29, 2011 Report Share Posted April 29, 2011 Hello I recently started a project, making a step motor controler board using IRLZ44 Mosfets (hex Mosfets) to control the power source to the motors. The way I understand them is they are either on or off no inbetween so if I set the circuit fo 12 volts when the mosfet is trigered 12 volts is sent. The board I am working on is using 5 volts for logic and 12 volts for the motor. Someware I read in order for the hex-mosfets to work the input voltage has to be twice the output voltage, so that would mean I would have to put 24 volts to the board, the step motors are only rated for 12. So back to were I don't know what I am doing. this is the board I am working on http://pminmo.com/3axis/3axis.htm thanks for any help you can offer.gogo Quote Link to comment Share on other sites More sharing options...
Hero999 Posted April 29, 2011 Report Share Posted April 29, 2011 You're wrong about how MOSFETs work. They have other modes of operation than just on and off. The gate voltage just needs to be high enough to allow enough current to flow through the load and a small voltage drop across the MOSFET. The maximum gate voltage depends on the device and normally varies between 10V and 20V depending on the device, see the datasheet. Quote Link to comment Share on other sites More sharing options...
gogo2520 Posted May 1, 2011 Author Report Share Posted May 1, 2011 thanks for the reply Hero999 I can see were I was wrong with the 24 volts, but it would still need a logic 5 volts to trigger it right. witch is ok because I need 5volts on the board to drive the rest of the logic chips. I guess I need to read some of the Pminmo help forms to see what they were talking about. Something about that particular mosfet. don't know I guess I will just have to read on. Studing the board as it is was worth the learning experience. But as soon as I figure out how the gates and the flip flops work together I plan on doing the driver a different way. The step motors I am using only need 12 volts at max so I could use a uln2803 for the drivers and I want to have opto isolation too. thanks again Hero Quote Link to comment Share on other sites More sharing options...
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