I am a rookie in this field. So please be gentle.
I am trying to turn ON / OFF (only ON / OFF) 12V LED Strip using arduino (and not even at high speed - ON/OFF transition after 15 seconds).
I did my homework and searched forums here and found out that I need a logic level mosef which has
1: Max gate threshold voltage (under 5V)
2: Low Rds (ON)
3: ID greater than my needs for LED strip.
I think that 2203 is better than 3205 because it has lower resistance but it is double the price and i need 40 pieces and I am on very small budget (it is home project)
Therefore I am asking you guys here to please help me and tell me if it is ok that i can order 3205?
It is a lot of money for me for my home project and I dont want to order wrong item.
In "Gate Threshold Voltage" it says MAX 4V. It concerns me. Does it mean that 5V of arduino will destroy it.
I know for someone who knows this stuff it is a simple answer. But please help me as I am a lot concerned.
Wow, those are some beefy mosfets! Are you really planning on running 100A? Even with a Ron of 7mOhm that's still a dissipation of 70W!
And you say not switch slow, no no dimming?
The L in IRL is for a logic level optimized mosfet. The Vgs thershold is very low. The IRF3205 is not optimized for logic level. As you can see in figure 3 you can have a Id of around 30A when you apply 5V. With the IRL2203 it's around 110A (given you can transfer the heat...)
But if the current isn't that absurd as the mosfets (aka more normal ledstrip currents...) are rated you might look at the
IRLML2502 45mOhm 4,2A
IRF7313 29mOhm 6,5A Dual channel
septillion:
Wow, those are some beefy mosfets! Are you really planning on running 100A? Even with a Ron of 7mOhm that's still a dissipation of 70W!
And you say not switch slow, no no dimming?
The L in IRL is for a logic level optimized mosfet. The Vgs thershold is very low. The IRF3205 is not optimized for logic level. As you can see in figure 3 you can have a Id of around 30A when you apply 5V. With the IRL2203 it's around 110A (given you can transfer the heat...)
I am sorry, i didnt mention current. My current needs are only 2AMP. So anything above that is fine.
septillion:
But if the current isn't that absurd as the mosfets (aka more normal ledstrip currents...) are rated you might look at the
IRLML2502 45mOhm 4,2A
IRF7313 29mOhm 6,5A Dual channel
Both are very cheap
Does IRF7313 has two mosfets in 1 ? Does it mean that I can buy only 20 mosfet instead of 40 in this one?
Please can you confirm me this ?
Yes, two MOSFETs in one package.
However: With Vgs = 4.5V, Rds will be 0.032 to 0.046 ohm with up to 4.7A of current - but for 300uS pulses not exceeding 2% duty cycle. Longer on-times at that current level and you risk burning up the chip.
I'd go with AOI-514, just 37 cents each for >25 quantity. Overdue for delivery at Digikey at the moment.
I use 32 of them on this board I offer. Traces were designed for 1A/channel continuous with 10A connectors to bring current in. The parts will handle more, I think if you had 2A on all channels at once things might get warm, you may need to add extra wiring over the traces to beef up current carrying capability and perhaps change the blue connectors to something more capable.
The board is designed to be daisychainable, so perhaps use two and spread the 40 channels out to use 20 per card, and just 5 channels out of each 8 for 10A max per group of 8. http://www.crossroadsfencing.com/BobuinoRev17/
Yes, 2 in one. You need 20 to drive 40 groups. It's a nice and easy package. And 50 will set you back $10,- on eBay. Or €0,37 a piece on TME (so €0,19 per group). Whole lot less then the €0,98 a pop for the IRL2203N.
CrossRoads:
However: With Vgs = 4.5V, Rds will be 0.032 to 0.046 ohm with up to 4.7A of current - but for 300uS pulses not exceeding 2% duty cycle. Longer on-times at that current level and you risk burning up the chip.
That's indeed the test condition for the Ron. But it tells you nothing about the driving limit... It can even drive 30A in pulses... Yeay, the Ron might not be the advertised 29mOhm with 5V but 46mOhm still isn't a problem. It will dissipate less then 200mW per channel @ 2A. Gives it a temperature rise of less then 25C. That's just fine.
septillion:
That's indeed the test condition for the Ron. But it tells you nothing about the driving limit... It can even drive 30A in pulses... Yeay, the Ron might not be the advertised 29mOhm with 5V but 46mOhm still isn't a problem. It will dissipate less then 200mW per channel @ 2A. Gives it a temperature rise of less then 25C. That's just fine.
To be honest, i do not understand what both of you are talking about. It is too technical for me.
What I can do is, i can tell you want I am using mosfet for.
I am trying to build a huge size 7 segment number.
The numbers will not pulse and they will remain ON for long period of time.
Number will increment only after 30 seconds.
Therefore my mosfet will not pulse. It will stay ON long time.
The mosfet will turn ON / OFF segment.
I hope now you are in better situation to advise me for AOI-514 or IRF7313
CrossRoads:
I'd go with AOI-514, just 37 cents each for >25 quantity. Overdue for delivery at Digikey at the moment.
Thanks for your input.
I checked the price for AOI514 at digikey.
The problem is that digikey charges me Shipping for AU$34.00. This ruins my budget.
If I order from ALIExpress it comes out at AU$0.71/piece
AOI514 I could not find on eBAY but IRF7313 was there on eBAY for AU$5 for 10 pcs (20 mosfets). It turns out to be AU$0.25/piece
From what I understand is that your concern is that resistance is too high and it will burn in long run.
Can you please advise some other mosfet which has low resistance and is cheaper than AOI514.
Thanks Larry for teaching me L means logic.
Thanks everyone for your help also. It is guys like you, smart and generous, that dumb guys like me get to make anything work.
I have searched a lot and I think I have found a mosfet that is logic level and has low resistance and is cheap and is available with free shipping to my country.
The mosfet is IRLB8721
I have seen it being used in Adafruit tutorial with arduino controlling RGB LED.
You agree that i can use it. Right?
Datasheet link is here
LarryD:
IRLB8721 looks OK
Why not use the IRLZ44N?
I can use IRLZ44N and it is the cheapest.
Just I thought that IRLB8721 has lesser resistance thus better.
I can be wrong also as I started learning this since yesterday.
What happend with the IRF7313? Did the calculation for you as well... With a tiny 2A I'm not concerned about the Ron at all... So you're obsession with a low Ron is totally unnecessary. Why would they otherwise make and sell them?
And wait, what?!
statbat:
Thanks Larry for teaching me L means logic.
Did you ignore all my posts? I told you that in relay 1!
Yes, you can use the IRLZ44N like a thousand other types. But I thought you wanted cheap... I give you some types, go to bed and wake up to see you ignore everything I post...
septillion:
What happend with the IRF7313? Did the calculation for you as well... With a tiny 2A I'm not concerned about the Ron at all... So you're obsession with a low Ron is totally unnecessary. Why would they otherwise make and sell them?
I am sorry I didnt mean to upset you.
I dont know much at all and I am only learning.
Crossroads said that it will burn and you replied to him saying about pulsing.
That is why I thought that may be it wont work as I wont be pulsing LEDs.
That is why I looked further in mosfets otherwise you are totally correct, you found me the cheapest solution. I just got confused that will it get heated or not.
septillion:
And wait, what?!Did you ignore all my posts? I told you that in relay 1!
YES you are right. When i woke up, i forgot that. I am sorry. You indeed were the first person to tell me that L stands for logic in the relays.
I am sorry that i forget the very next day. I feel even more stupid now
septillion:
Yes, you can use the IRLZ44N like a thousand other types. But I thought you wanted cheap... I give you some types, go to bed and wake up to see you ignore everything I post...
I m ordering 7313 as it is cheapest of all and you seem pretty confident in it so i am confident.
Thanks again and sorry again
But no, they will not burn. 2A is just a tiny amount of current really... They are designed for 6,5A and up to pulses of 30A. Okay, they might get a bit to hot then but I don't see a problem with 2A, even if the Ron is a bit higher then the advertised. The heat dissipation still is pretty insignificant.
And yes, they are surface mount, don't know if that's a problem. But I find a SO-8 pretty easy to solder, especially on a PCB with soldermask.
It's just one of the types I found and find nice to use. Most of all because they are cheap but they are easier so solder then SOT-23 as well etc. So just a nice type to remember in opinion.
