I got this, as well as heat sinks to run 24V water pumps.
It says it can handle 24V, but the data sheet for the IRF 520N lists plus or minus 20V as the max V gs.
The 24V pumps are well under the max A, but now I'm not sure the IRF 520N can handle 24V.
If I could get an opinion as to whether the IRF 520N can handle 24V, I would appreciate it.
It says it can handle 24V, but the data sheet for the IRF 520N lists plus or minus 20V as the max V gs.
When driving it with the Arduino, the gate voltage is 5V.
As DVDdoug points out, the gate voltage is 5v, HOWEVER, you specified it was an IRF-520 - you can't turn it on completely with a gate voltage of 5v so you will have problems with heat/control. What you want is an IRL-520 which is spec'd for a gate voltage as low as 5v (the "F" version requires 10v while the "L" version is spec'd for 5v - see http://www.vishay.com/docs/91298/91298.pdf for more info. According to that data sheet, the Vds (drain-source which is what you are controlling) is rated at 100v.
gpsmikey:
(the "F" version requires 10v while the "L" version is spec'd for 5v -
I wasn't aware that 5V would cause trouble switching the IRF-520. I was worried about driving a 24V pump with it....
Anyway, is 10V a minimum? I ask because if so, maybe I could power an UNO and 12 of these modules I bought with a 12V 1A wall wart that's laying around.
Thanks guys.
See Q8 example for driving:
.
saltyjoe:
I wasn't aware that 5V would cause trouble switching the IRF-520. I was worried about driving a 24V pump with it....Anyway, is 10V a minimum? I ask because if so, maybe I could power an UNO and 12 of these modules I bought with a 12V 1A wall wart that's laying around.
Thanks guys.
Take a look at Fig 3 in the link I provided above in #2 then look at the same figure 3 in the IRF 520 datasheet at http://www.vishay.com/docs/91017/91017.pdf notice the for the IRL, the transfer is showing for up to 5v on the gate, but on the IRF, it goes up to 10v to turn it on. If you use an additional control transistor like Larry showed in his schematic which does provide the 10v to the gate, then IRF is fine, but driving it directly with an Arduino which only has 5v (max) output, will not turn it on completely unless you use the "L" (Logic) version.
max gate voltage (Vgs) is nothing to do with the load.
The max gate-source voltage is a limit you must observe or you risk instantly blowing the gate oxide,
whether or not there is any load - this is just like overvoltage damage to a capacitor. Once you do this
the gate is no longer isolated from the source and drain and you have a crippled device. If the device is
switching high power gate-oxide failure will then lead to catastrophic failure.
The drain-source max voltage (Vds) is defined as the point where the drain-source leakage current rises above
some nominal point, with the device hard-off (Vgs=0). Some devices can take a certain amount of breakdown
energy if this is exceeded, as used with ignition systems. Too much energy will simply overheat (melt) the
device (or even explode it).
The IRF520 is not logic-level, it needs Vgs >= 10V to turn on (nominally 12V). You've been
sold a lemon.
Logic level devices often have a Vgs requirement of >= 4.5V (nominally 5V).
You guys saved me a lot of grief pointing out the problem with switching IRF 520 with 5V. Thanks a ton! Also, now I know what Vgs means-thanks for that too.
It is bogus to sell that module with an IRF-520 and say to use 5V. Would you guys take a look at the hookup scheme I attached?
I'll have twelve pumps, with a dedicated 24V power supply for each pump. The 12V power supply is 1A.
All twelve pumps will run at the same time for 2 minutes every 6 hours, otherwise 6 pumps will run at a time.
BTW LarryD, all I could make out in that schematic is the M inside a circle-must be my computer-it's getting old.
CCF07012016_0000.pdf (358 KB)
BTW LarryD, all I could make out in that schematic is the M inside a circle-must be my computer-it's getting old.
Thanks, now I can see the schematic.
OK, I was hoping 12V would do the heavy lifting for the switch and the signal from Arduino would tell it when to do so. Three views of my scheme and no comments makes me think you guys are being nice. (:
The next easiest fix that I can see is to replace the IRF-520 on my modules with IRL-520. Assuming everything on the module is hooked up correctly, would that likely do the trick?
Yes, the IRL520 is logic level. However its a truly ancient device, modern MOSFETs are literally 100's of
times better (lower on-resistance)
Any ballpark idea how much energy would get wasted to heat driving a 24V, 1A pump with a IRL520?
I searched 5Vgs mosfet and got a zillion hits...I won't ask anyone to search for me, but if off the top of your head you have a recommendation for my application, please post.
power = I-squared-R. energy = power x time.
On the IRL520 datasheet, http://www.vishay.com/docs/91298/91298.pdf fig. 3, it shows more than 10A flow at 5Vgs. Since my pumps are about 1A, I'm hoping for no heat issue there. Fig. 6 shows voltages a lot higher than my 24V pumps, so I'm thinking all is good there. I don't know enough electronics to read datasheets well, so I'll go with the IRL520 rather than take a chance on a more efficient mosfet.
If I were to power an Arduino UNO with a 9V 1A power supply, would connecting all twelve IRL520 mosfets to UNO's 5V pin push too much current through the UNO? All twelve pumps will run simultaneously for a few minutes every six hours.
If you look at the data sheet, under "Specifications" one of the test conditions they show lists what to expect for the RDS (effective resistance from the Drain to the Source). In this case, for 4v VGS with ID = 4.6A, they show a max of 0.38 ohms for RDS, which, when you plug that into the power equation (see Mark's post #12), using 1a which you say is typical for the pump, you get about 1/3 of a watt (I like to use the 4v instead of the 5v test case to be safe - you don't know if it is going to be fully driven to the 5v - I always design to the safe side). You should have a current inrush limit resistor between the Arduino output pin and the MOSFET gate because, while a MOSFET is a voltage controlled device, it has significant capacitance on the gate and you need to limit the charging current to safe levels from the Arduino. Otherwise you can drive all of the gates from one pin although, if you are turning them all on at the same time, why are you not using one MOSFET to control all of them ? (if they each take 1a running, the starting current is probably 2 or 3 amps, so for all of them, you would need a MOSFET rated for something like 30A. A IRL520 is rated for 9A, so you could probably safely drive 4 or 5 pumps in parallel with one transistor.
Thank you for all that good info. Since almost always only six pumps will be running, that's a waste of probably less than 2W. I can live with that.
I checked the IRF 520 module and there is a 1K resistor between the gate and sig pin. Does that sound about right?
I have dedicated mosfets because the pumps are doing different things at different times. It's cool to be able to scratch the surface of the magic of Arduino. A very simple sketch too...for most people anyway, ha.
Each pump has a dedicated 24V power supply. Is there any reason to connect the negative side of those 24V power supplies to the negative side of the 9V power supply that will feed the UNO?
You must common the grounds - MOSFETs are not isolating, the source is common to both
controlling and load circuits.
If you are running PWM then change that 1k to 150 for less switching loss.
Oops, the 1K resistor is between the ground pin on the IRF module and the gate. There is 1 ohm resistance between the sig pin and gate.
I'm thinking I should ditch these modules....do you agree?
Yes
Dr.Azzy, a solid contributor, makes a line of MOSFET boards.
He does good work.
