planning build mosfet h bridge motor control


Posted on Feb 7, 2014

At 9 volts the maximum stalled current of the motor types I`m going to use will be 700 mA. Since I`m not real experienced with this I want to check that I`m choosing good mosfets, I`m pretty clear on the rating, they say what current and voltage they can handle. But I`ve found with some the mosfets, particularly P type, the RDS (on) is fairly high for the low current ones. Now intuitively one assumes that you want


planning build mosfet h bridge motor control
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the smallest that will work for energy efficiency, that would be the case with some relays, but if I get a to-220 p channel mosfet that handles 1 amp, the best I can find is about 2 ohms RDS, If I go up to 13 amps, I can find one thats just 0. 009 ohms RDS, and it isnt even that expensive, 91 cents ( heres a transistor of that description, datasheet ). So from what I`ve learned so far, this would be a good choice, its go a wide factor of safety over the 700ma max im going to draw, and it should eat up a lot less power as heat because of its low RDS. While I probably misunderstand something here, I can learn from you guys telling me what I got wrong. I`ll come back and put the datasheets for the specific P and N type mosfets I plan to use once I get them picked out, for now I want to make sure I`ve got the theory right. The L298 is a dual full H-bridge capable of 46V at 4A max. It doesn`t care for the "not allowed" status, moreover it takes care of fast motor stop if inputs A and B are equal, no matter if they are high or low. An additional option is free running motor stop using the ENABLE input. 2. 5W and higher power resistors are not available as carbon (the worst choice since resistance increases considerably with in increasing temperature) or metal film resistors. Using a 5W wire wound resistor will be OK if nothing else is available. Applying PWM special care must be taken not to have both inputs at the same level...




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