ARDUINO PWM should drive a opto coupler, and that is controlling the MOSFET, ( and i think i see 2 resistors in the circuit )
After some sleep and some more reading, I think it's because with the 5v from the arduino and 12v supply I can only get the Vgs to be -7V and I want it to be 0 to turn off the supply.
Would this be ok running PWM, as it has the 400 instead of the 10k, so should respond quicker?
Quote from: jimmy__riddle on Mar 30, 2012, 01:05 amWould this be ok running PWM, as it has the 400 instead of the 10k, so should respond quicker?Sorry, I wasn't catching on that you were using PWM :-) 400 Ohm may be sufficiently low for the default PWM frequency of the Arduino, at about 490 Hz. Less would be better, but keep a finger on the transistors, and you can tell if they get too hot pretty easily (and turn off the experiment.) However, if you power at 12 V, with 400 Ohm, that'll dissipate more than 1/4W, which is the most common resistor capacity. Make sure you get resistors that can "take the heat" so to speak.However, if you have optocouplers, how about using two, with an inverter into one of them instead of the resistor? Assuming the resistance of the optocoupler is low, that will be a significantly better design. Similar to CMOS in a way :-)
Ok, I'm a beginner at this, but trying very hard to learn. I'm trying to use my arduino uno to control a peltier, and I am planning on using an H-bridge from two N and 2 P ch MOSFETs.
The best thing to do is probably to isolate the gates for the two transistors, and use two digital out pins. This will let you turn one off before you turn the other on, thus preventing shoot-through. It would also let you turn the entire thing to the "off" state rather than driving one way or the other.If you really want to use only one control pin, then any kind of inverter will work. An opamp (MCP602) with the signal into the negative pin and the positive tied to a midpoint resistor ladder, for example. Or a 7400 NAND gate with the two inputs wired together. Or a single N-channel MOSFET, such as the BS170.