Hi All,
First time poster long time lurker.
I’ve been toying with a MOSFET driven motor and some PWM off of a Raspberry Pi. The PI is putting out 3.3v and the motor is a 12-28V DC with at least 10A draw. I choose the FQP30N06L (https://www.sparkfun.com/products/10213) for the logic level gate and high drain-source current. However, I was having difficulty (blue smoke) using a single MOSFET with a high side load and powering the motor at 28V. Researching lead me to believe that the MOSFET might be in the linear region with a higher than anticipate Rdson - which jived with my burnt fingers (was using hefty heat sink and thermal paste).
I decided the fix was a level shifter to get firmly in the active region. However, I was also impatient and figured using another MOSFET I could achieve basically the same end. See link for pic.
http://i57.tinypic.com/33djsph.jpg
Using the first to switch in the voltage divided 28V source (should be around 10V, exact value shouldn’t matter). Checking the circuit I connected the 3.3V in and GND lines to effectively shut of the first stage and ‘full on’ the second. The fluke shows ~10V at the R1 R2 junction, however, the second transistor doesn’t seem to come fully on at all. In fact, the total draw (as referenced from my bench supply) is only about 0.8A and the motor doesn’t budge. Another curious output was the D-S voltage (with 10V G-S) was like 600V (probably a fluke Fluke?).
Being NOT an EE I turn to you all for some quick insight. Where did I go wrong and how do I drive this large(ish) motor? Bonus points for solutions including only the referenced MOSFET and resistors…as that is what I have on hand today!