Im planing to control my 12 volt 1A led panel. so i need to use mosfet
And after searching around the forum i found this thread and found out that the best mosfet for arduino is the one with 5V VGS but thats not all. one of the user mentioned this:
Here's a quick guide to choosing a mosfet:
Choose a logic level mosfet - that is, one who main specifications are given at Vgs=5v, not Vgs=10v.
Choose a mosfet whose Vds(max) rating is comfortably above the voltage you want to switch.
Choose a mosfet whose Ids(max) rating is comfortably above the current you want to switch.
Choose a mosfet whose Rds(on) at Vgs=5v is low enough that for the current I you want to switch, the power dissipated when the mosfet is on, given by I^2 * Rds(on), is low, for example below 5W.
Can you help me undersstand the last point?
And from this website LINK, He used a RFP30N06LE mosfet with 10V VGS and he said that this mosfet is great to be used with arduino which contradict the first point from the quote.
Can you help me to understand the datasheet? what do i need to look on the datasheet to determine whether or not the mosfet is suitable for arduino and my project.
Thanks and English is not my first language so please tell me you don't understand my question
Can you help me to understand the datasheet? what do i need to look on the datasheet to determine whether or not the mosfet is suitable for arduino and my project.
You are misunderstanding the data sheet. The 10v GS is an absoulute maximum rating.
Take a look at the Drain to Source on Resistance (Rds-on) which is .047 ohm at 5v.
Also look at figures 8 and 9 which show the drain/source characteristics at gate/source 5v.
Just recently I made an Arduino control a RGB LED Strip with a common anode. I used 3x IRLZ44N MOSFETs to adjust the brightness of each individual color. It fits perfectly the task. Doesn't heat up even a bit, works great with PWM, at both high and low duty cycles.
Now, choosing a MOSFET can be tricky. Most IRLZ-series MOSFETs are logic-level-driven. Which means the threshold voltage on the gate to open the flow is about 1V and has decent performance at a 5V, allowing for high current to flow, without dissipating much heat.
I'm not a pro at these things, found out myself by just experimenting with different kind of MOSFETs. If i'm wrong - please, correct me.
cattledog:
You are misunderstanding the data sheet. The 10v GS is an absoulute maximum rating.
Take a look at the Drain to Source on Resistance (Rds-on) which is .047 ohm at 5v.
Also look at figures 8 and 9 which show the drain/source characteristics at gate/source 5v.
The RFP30N06LE is suitable for a 5v arduino
Thanks for the answer, So RDS on will show the optimal voltage to used with the mosfet? am i correct?
And can you explain more about figure 8 and 9?
Ghostt:
Just recently I made an Arduino control a RGB LED Strip with a common anode. I used 3x IRLZ44N MOSFETs to adjust the brightness of each individual color. It fits perfectly the task. Doesn't heat up even a bit, works great with PWM, at both high and low duty cycles.
Now, choosing a MOSFET can be tricky. Most IRLZ-series MOSFETs are logic-level-driven. Which means the threshold voltage on the gate to open the flow is about 1V and has decent performance at a 5V, allowing for high current to flow, without dissipating much heat.
I'm not a pro at these things, found out myself by just experimenting with different kind of MOSFETs. If i'm wrong - please, correct me.
I just checked the IRLZ44N and it can be used for arduino thanks.
ice856:
So RDS on will show the optimal voltage to used with the mosfet? am i correct?
Rds on shows the internal resistance from Drain to Source, in dependence of Gate voltage. Higher the resistance - more heat is generated at high current draw - higher the losses. With higher resistance or high current you may want to attach a radiator to the mosfet. Should not be the case with a simple led strip.
Choose a mosfet whose Rds(on) at Vgs=5v is low enough that for the current I you want to switch, the power dissipated when the mosfet is on, given by I^2 * Rds(on), is low, for example below 5W.
Can you help me understand the last point?
When you turn on the MOSFET it acts like a low-value resistor. Like any resistor it turns some of the power (Watts) into heat. Too much heat and the MOSFET is destroyed.
To figure out how much power (Watts) is being turned into heat, square the current (Amps) and multiply by the resistance (Ohms).
To find out how hot the MOSFET will get, multiply the power (Watts) by the thermal resistance from junction to ambient (from the datasheet). That will give you the temperature rise (how much hotter the silicon is than the air around the MOSFET). Add the ambient air temperature (about 20°C for room temperature) to get the junction temperature and make sure it isn't going as high as the maximum allowed junction temperature (from the datasheet).
If the MOSFET would get too hot you can add a heatsink to reduce the thermal resistance or use a MOSFET with a lower ON resistance.
I'm going to suggest you consider a "hybrid" approach, in this case using a transistor to control a MOSfet. This will immediately widen your choices of the FET, and just about any NPN transistor will work. In the example I've posted here ("I'll post a link, because this arduino editor does not offer me a way of posting an image directly), an NPN transistor is used to control an N channel Mosfet. The Transistor used for Q1 does not have to be the one shown. Acommon 2N2222 or just about any general purpose NPN transistor will do fine. For M1, an IRF8244 (SMT), maybe an an MPF102 if you prefer a discrete. Lots of choices. This Hybrid approach will make it much easier to control loads directly from a 3.3V output such as the ones offered in the Arduino line.
I prefer to go for a logic level MOSFET, and have no problems switching LED loads of 4-5A and pumps drawing about 2A with a 3.3V signal.
The main problem is that many such MOSFETs only come in SMB packages (so by now I'm getting quite skilled at soldering SOT-23 packages on perfboard - it's quite amazing how much current those tiny things can switch), but you may also look into the RFP30N06LE as mentioned before, a VGS, th of just 1-2V means it may do just fine for 3.3V loads, and it comes in convenient TO-220 package.
Both DigiKey.com and Mouser.com have parametric searches. You select your requirements and it shows you what parts they have that meet those requirements. DigiKey.com, for example, shows 98 devices when you filter for:
Through-hole devices
N-channel
Drive voltage for minimum RDS(on): 4V, 4.5V, or 5V ("Logic Level")
Add filters for voltage and current to narrow down the choices from there.
