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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #41  
Old 12-18-2008, 06:55 PM
slisgrinder slisgrinder is offline
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yup that looks great. now onto the driver circuit...since i already ordered the mosfets (IRF540), what is a driver circuit anyway...

since the arduino supplies 5V at 40mA max to the gate, do i really need a driver circuit?
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  #42  
Old 12-18-2008, 07:16 PM
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Originally Posted by slisgrinder View Post
yup that looks great. now onto the driver circuit...since i already ordered the mosfets (IRF540), what is a driver circuit anyway...

since the arduino supplies 5V at 40mA max to the gate, do i really need a driver circuit?
IRF540 MOSFETs are standard N-channel MOSFETs. They will not work properly unless Vgs reaches 10v. This is why I specified logic level MOSFETs.

Now, IRL530's, IRL640's are also logic-level MOSFETs. Notice the "L" instead of the "F". That one letter makes a big difference.

Ordering the wrong MOSFETs will cause the circuit to be unnecessarily complicated.

Why don't you order some IRL530 or IRL540 MOSFETs from Digikey? They will ship them quickly, and this will keep your project much more simple.
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  #43  
Old 12-18-2008, 07:22 PM
slisgrinder slisgrinder is offline
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what about an irl510?
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  #44  
Old 12-18-2008, 07:27 PM
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what about an irl510?
That might work, but it has a much higher Rds(on) than the 530's and 540's. This means more power loss in the MOSFET, which means greater power dissipation. If you want the MOSFETs to run cool (which you do!) then use MOSFETs with a low Rds(on).

The IRLZ24 and IRLZ34 are less expensive than the IRL530/IRL540. But for some unknown reason, you seem to like to choose other parts than what are recommended.
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Old 12-18-2008, 07:36 PM
slisgrinder slisgrinder is offline
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well, the irf540 are on their way...i guess i will have to use those...the supplier (lee electronics, the closest to where i live (calgary)) only has irl510 but not in stock so i guess i will have to use a driver circuit and stick with the irf540...
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  #46  
Old 12-18-2008, 07:42 PM
slisgrinder slisgrinder is offline
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so what is a driver circuit anyway...
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  #47  
Old 12-18-2008, 07:47 PM
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A driver circuit translates the 0v-5v output of your Arduino uC to the 0v-10v required by the MOSFET gate.
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  #48  
Old 12-18-2008, 07:52 PM
slisgrinder slisgrinder is offline
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how do you accomplish this? by having a transistor, and since this is a pwm signal, a transistor wouldnt work so...what am i suppose to do...i thought the gate-source voltage was +-20V?
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  #49  
Old 12-18-2008, 08:09 PM
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See the attached schematic.

V1 is just a signal generator, but it represents the 0v-5v output of your Arduino uC.

The rest is to handle the charging/discharging of the MOSFET's gate.

The 1N4148 really should be a 1N4150. A 1N4148 won't handle enough current.

R5 represents the load.
Attached Images
File Type: png MOSFETdriver.PNG (58.5 KB, 17 views)
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  #50  
Old 12-18-2008, 09:02 PM
slisgrinder slisgrinder is offline
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so this schematic you just made it for the irf540? wow, thats cool...
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