Odd. I can only speculate that 0.1Ω is maybe not enough to shut down the one transistor that is hogging the current. Try a 0.2Ω if you have one.Even with .1Ohm ballast resistors and separate base resistors, one of the transistors steals all the current and burns up. I would think that if one had a breakdown the other one would be a little bit hot but I tried this with 3 transistors and 2 were cold, as if they never got any current.
If your only going to use 5 volts to drive them you probably should use logic level FETS.I'll try some of the suggestions. Yes I have a normally spec'd diode for 48V solenoids. I don't recall specifically which one.
I had some leftover IRF3205's and I picked up an NTE2390 today. Both MOSFETS.
Confusingly, the NTE2390 I can pull massive current (10A) for at least 5 seconds (probably more) and I tried on two of them. Both good. It gets hot but it doesn't break down. However, my old IRF3205's still will never work. They die immediately and I'm looking at the datasheets and they look pretty similar. I bought the IRF3205 off ebay so they could just be bad as people say dont buy off Ebay, but these guys look pretty similar on the datasheet. The RDS on the NTE part says .2, but I dont know if that is .2 milliOhm or what. If so that would make sense that it doesn't have as much resistance and why it holds up so well.
I'm putting 5V on their gate. Both TO-220 packages.
nte2390 is not a logic level Vgs and the Vgs=±10V, so when the Vgs=3.3V then the Rds will be too high and the Vds also too high as 3V, please check the "Drain−Source ON−Voltage" on page 2.
irf3205 I can't find the info to shows that it is a logic level Vgs, but the Vgs=4.5V, you still can get the Ids current as 25A, when the Vgs<4.5V then I can't the useful information.
Page 2 -- RDS(on), Static Drain-to-Source On-Resistance ––– ––– 8.0 mΩ, Vgs = 10V, ID = 62A.
SUP85N10-240141 -- When the Vgs <3.5V then maybe it is not a good choice for this application.
View attachment 179358
SSR-40DD 40A -- if you want then maybe it is suitable for you.
Another choice is that to use a stage of npn bjt (ie : 2N3904) and a P MOSFET, Vds>=48V*1.5V, Ids(on)>=12A, Rds(on)<=12 mΩ.
I'm putting 5V on their gate. Both TO-220 packages.It's painful to try to drive a low-side NFET or Transistor with 3.3V logic, especially when several amps are involved.
If it's a FET, you have a very limited selection of devices that can turn fully ON with 3.3V.
Transistors need substantial base drive current, hard to get from a 3.3V IO pin.
IF... you can configure your coil for a high-side switch (one side of the coil grounded), this circuit will do the job nicely.
The NPN transistor acts as a current sink and level shifter for the FET, it pulls around 5 ma into ground, which provides a nice 12 volts Vgs on the FET, regardless of the 48 V supply. (2400 ohms X 0.005 A = 12V)
Now the selection of the FET is easy, with a solid 12V on the gate, there are zillions of PFETS to chose from.
The only caveat is that it's not blazing fast, as long as you are not trying to do Khz PWM on the coil, it's plenty fast enough.
You still need a logic level MOSFET. With only 5 volts on the gate, the MOSFET won’t turn fully on and at your high amperage, will soon overheat. And could burn up.I'm putting 5V on their gate. Both TO-220 packages.
Did you notice, the circuit design on the older shematics ...Actually on NTE's website their product says .2Ohm for RDS(on), so that's interesting.
I knew that you were put the 5V on gate, what I thought was that the 3.3V is came from I/O port of uC, so I will count the Vin as 3.3V, 5V just for test, if the TS want to use 5V as Vin and shift 3.3V to 4.5V or 5V then use SUP85N10-240141 should be OK.I'm putting 5V on their gate. Both TO-220 packages.
Although the datasheet of SUP85N10-240141 didn't mention that it is a logic level MOSFET, but it was mentioned like there:You still need a logic level MOSFET. With only 5 volts on the gate, the MOSFET won’t turn fully on and at your high amperage, will soon overheat. And could burn up.
You need a component that satisfies all of your requirements. I looked for logic level n-channel MOSFET rated for at least 60V and more than 60A.
Here is a logic level n-channel MOSFET that satisfies those requirements.
Yeah, your right. We have both numbers.I knew that you were put the 5V on gate, what I thought was that the 3.3V is came from I/O port of uC, so I will count the Vin as 3.3V, 5V just for test, if the TS want to use 5V as Vin and shift 3.3V to 4.5V or 5V then use SUP85N10-240141 should be OK.
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by Jake Hertz