hello, glad I found this forum!
I am working on a project and need some assistance.
I want to build a simple MOSFET switch to switch on a high current (up to 5A) load from a micrcontroller (arduino) 5V logic outputs. here are my specs and requirements:
standard 5V logic outputs from the microcontroller to my switch, 0V off, 5V on.
I must switch the positive, not the negative, so I have to use a P channel mosfet
for saftey reasons, I need my outputs to fail off, the microcontroller fails to off, and I need my output to fail to off (ie, positive trigger, positive output) so my plan is to run the arduino digital output through an 74HC04 inverter, then connect that to the gate of the MOSFET.
the load runs off a different voltage than the microcontroller, I need to switch approximately +12 to +15VDC.
I do not want the circuit dependent on the load current, I want to make transistor outputs capable of operating devices at 12-15VDC drawing anywhere from a few milliamps up to 5A of current.
is doing this just as simple as using a logic level P channel MOSFET with a drain/source rated for >5A (I want one rated for 10 just in case) and 15+ volts?
then making the connections: arduino output to inverter input, inverter output to MOSFET gate. MOSFET drain to the +15V/5A output to have the load connected, and the MOSFET source connected directly to the +15V source? is it really that easy?
do I need resistors anywhere like on the gate? my understanding is that a logic level mosfet can be connected directly up to the IC's output is that correct?
something like the 12V pic sample on this web site:
http://digital-diy.com/general-electronics/67-tip-logic-level-fets-p-channel.html
except couldn't I do away with the NPN using the inverter instead? are the resistors still needed?
can someone please help me design this circuit? and I'd really appreciate some help with selecting a MOSFET that will do the job. I'd prefer a TO-220 form factor device.
the above is what I really need help with but another related question:
these outputs may also be powered by other sources. if the transistor output were on or off and the output received +12-15V from some other source would that cause any problems? if so would just inserting a properly rated diode on between the transistor and the load solve the problem preventing any backfeeding of voltage from other sources? I'd rather avoid that if I don't need it to prevent the voltage drop, but if its needed I can add it.
thank you in advance!
I am working on a project and need some assistance.
I want to build a simple MOSFET switch to switch on a high current (up to 5A) load from a micrcontroller (arduino) 5V logic outputs. here are my specs and requirements:
standard 5V logic outputs from the microcontroller to my switch, 0V off, 5V on.
I must switch the positive, not the negative, so I have to use a P channel mosfet
for saftey reasons, I need my outputs to fail off, the microcontroller fails to off, and I need my output to fail to off (ie, positive trigger, positive output) so my plan is to run the arduino digital output through an 74HC04 inverter, then connect that to the gate of the MOSFET.
the load runs off a different voltage than the microcontroller, I need to switch approximately +12 to +15VDC.
I do not want the circuit dependent on the load current, I want to make transistor outputs capable of operating devices at 12-15VDC drawing anywhere from a few milliamps up to 5A of current.
is doing this just as simple as using a logic level P channel MOSFET with a drain/source rated for >5A (I want one rated for 10 just in case) and 15+ volts?
then making the connections: arduino output to inverter input, inverter output to MOSFET gate. MOSFET drain to the +15V/5A output to have the load connected, and the MOSFET source connected directly to the +15V source? is it really that easy?
do I need resistors anywhere like on the gate? my understanding is that a logic level mosfet can be connected directly up to the IC's output is that correct?
something like the 12V pic sample on this web site:
http://digital-diy.com/general-electronics/67-tip-logic-level-fets-p-channel.html
except couldn't I do away with the NPN using the inverter instead? are the resistors still needed?
can someone please help me design this circuit? and I'd really appreciate some help with selecting a MOSFET that will do the job. I'd prefer a TO-220 form factor device.
the above is what I really need help with but another related question:
these outputs may also be powered by other sources. if the transistor output were on or off and the output received +12-15V from some other source would that cause any problems? if so would just inserting a properly rated diode on between the transistor and the load solve the problem preventing any backfeeding of voltage from other sources? I'd rather avoid that if I don't need it to prevent the voltage drop, but if its needed I can add it.
thank you in advance!