MOSFET Suggestions for LED Dimmer

Other Hardware LEDs and Multiplexing
1

I am very new to electronics and have had fun making a number of escape room games for my kids with a Uno and Nano. Now I'd like to try my hand at making some Halloween props.

I am starting to develop ideas for a Giant Spider Halloween Prop. I was hoping to do some multiple LED eyes that would dim up and down. Here is an image for inspiration that looks similar to what I am thinking about:

Screen Shot 2022-01-15 at 3.00.37 PM
Screen Shot 2022-01-15 at 3.00.37 PM914×598 40.7 KB

To control this I would like to use an Nano, here is a rough sketch from TinkerCAD of the concept of how I'd like to wire it up (I put a pot in there for now but will write dimming code later once I find levels I like):
Screen Shot 2022-01-15 at 4.06.48 PM
Screen Shot 2022-01-15 at 4.06.48 PM1894×1210 228 KB

Here is the schematic from TinkerCAD:
Screen Shot 2022-01-15 at 4.08.09 PM
Screen Shot 2022-01-15 at 4.08.09 PM1724×1332 161 KB

I was going to use some 3mm red LEDs with Input voltage: 1.8-2.2v, and Input Current: 20mA. I thought these would look good and are a reasonable a price on Aliexpress Aliexpress.

I'll likely have 10 to 20 leds that will be controlled (200-400mA).

Probably doesn't matter but here is some code of how I will test it:

#define MOSFET_Signal_PIN 6  // output to FET
#define POTM_PIN A0  // potmeter analog input 

byte pwm;

void setup()
{
  pinMode(MOSFET_Signal_PIN, OUTPUT);
}

void loop()
{
  pwm = map(analogRead(POTM_PIN), 0, 1024, 0, 256);
  analogWrite(MOSFET_Signal_PIN, pwm);

  delay(100);
}

I was hoping to get some advice on:

  1. What MOSFET would be best for my application so that I could order some from AliExpress? I was looking to get something I could use for this but also maybe get some extra for some simple 5v, 6v, and 12v devices like a mag lock.
  2. Do you see any issues with my basic concepts?

Thank you for your help.

Greg

2

Make sure you get a logic level FET, one where in the data sheet it says what the Rds is when it is fully on. Make sure this is for a gate voltage of 5V and not the normal 10V.

3

I trust you have realised by now that the Nano is far more useful than the UNO? :grin:

If you drive all those LEDs (as many as 64 but you do not need that) with a MAX7219 then you can dim the whole array to a certain extent (16 steps but the higher ones will be indistinguishable) and make individual LEDs flicker or move around.

Best to buy a couple of the matrix modules unassembled and wire your own LEDs as a matrix instead of installing the square ones in the kit; it's cheap enough anyway .

4

Are there any models you would suggest? There are so many it’s hard to choose which one is best.

5

No, because there are so many it depends on what you can get hold of in your part of the world. Where ever that is.

6

I was thinking about a 2N7000 like this:
Aliexpress 2N7000

Do you think it might be a good choice?

7

No, that device can only handle maybe 100 ma.

I doubt you will find a logic level MosFet at Aliexpress. They usually have older parts.

What part of the world are you? I purchase a lot of my specific parts at Digikey in the USA. Does that work for you?

8

Really?

9

FYI

image

10

Instead of a suggestive "Really?" I suggest you post something useful.
If I'm wrong about Aliexpress please show a link I may have missed. I for one would be appreciative.

11

You can't see a link? On my Firefox it shows up in blue. :sunglasses:

12

I stand corrected, thanks for the link :slight_smile:

13

And that is only the first listing for that FET, which was discussed on another thread and seems to be an extremely useful 3.3 V logic-level device. :+1:

The trouble is that the search engine on Aliexpress is truly abysmal and seems to have become even more dreadful over time, so the only reason I found that device is that following the discussion on the other thread, I searched for it by part number - and even then what the search brings up is confounded by mounds of total garbage. :grimacing:

14

Thank you for providing a device, I will look at the IRF7401TRPBF and variants on Ali. Agree on Ail search engine, I usually use google by part number and if you can find one on Ali it will list a bunch of other suppliers as suggested sellers below at the bottom. Other issue with Ali they never have data sheet info and they will list 5 to 10 similar parts so you're no sure which one you're getting. I could go on but the price is so good on Ali for me in Canada for my one off projects that as long as I'm patient I can get amazing value for the $.

15

I took a look at the spec sheets ... I have been looking at the IRL540, would there be any issues with using that?

16

I'm in Canada, I can get stuff at DigiKey but it's 10x the price of AliExpress. For my one off hobby projects (mostly escape rooms and Halloween props) that really only need to work for a couple of hours, I try and keep the price low by planning them months in advance and then wait the 60 days or so for the stuff from Ali. Some stuff is better from DigiKey like the Teensy which is twice the price on Ali but most of the stuff on DigiKey is 10x or more than Ali.

17

For me (in Canada) I can also get the IRF520 (not IRL) module on Ali for less that $0.50CDN. IRF520 Module on AliExpress

Any thoughts on this? I assume it will be fast enough for PWM dimming of the LED, but as a module not draw much? Size is not an issue for me for this project. Any downsides to using this as a MOSFET?

18

It is no use for what you want. It is not a logic level FET you need 10V on the gate to turn it on and the on resistance when you do is very high.

19

This is certainly confusing for a noob like me ... Where do I find that info? I found a data sheet here: IRF520 Datasheet

Are there a couple of MOSFETs that you might suggest I look at as good options? Do you think the IRL520 would be a good choice?

20

Canada here too.

IRL540, IRLZ44N, RFP30N06LE many more all available at Amazon.ca.