LED Dimmer with NMOS

321

11:35:32

Again, found a video online to attempt to learn more of the "why" and less of the just making it go version of things.

https://www.youtube.com/watch?v=kPyBkjgl5bI

Attempted to simulate the circuit, but failed again...  this circuit requires the use of the Body or Bulk connection on the MOSFET, but I have no idea where that is (or how to fake it).

I'm also certain I didn't understand the air wiring correctly in the video.

UPDATE - This circuit is now working thanks to the help of feedback from the community.

published 5 years ago

Redstone_guy

5 years ago

Voltage source is too high for the LEDs to handle

Beaker651

5 years ago

The reason is because you need to use current limiting resistor for your leds

NarWhale

5 years ago

Oh yeah, I get that the voltage is too high, and I figured that there should be current limiting resistors for the leds, but if you look at 10:21 in that video you can see there is only one resistor in his air wired model. Also, you can see in the video that he is using the Body of the MOSFET as part of the circuit. Can this be done in EveryCircuit? I wasn't able to figure out how.

BillyT

5 years ago

I think this is the circuit you were aiming for, top button makes the leds brighter, bottom button makes the leds dimmer. http://everycircuit.com/circuit/6473555568754688

BillyT

5 years ago

In this circuit the body of the fet is connected internally to the negative pin, check the devices spec sheet. And depending on the fet specification I would probably use more leds or a current limiting resistor.

NarWhale

5 years ago

BillyT: thank you for the example. What you show makes more sense than the circuit in the video. Perhaps the video one works, but I can understand yours better.

NarWhale

5 years ago

BillyT: I took what I saw in yours and I believe I have rebuilt it so it is staying within the general parameters and intent of the one I saw in the video: 12VDC, 3 LEDs, dim and bright, don't explode LEDs.

NarWhale

5 years ago

So the only difference between this version and the one in the video is we are using one more resistor, and we aren't bothering to use the Body of the MOSFET.

BillyT

5 years ago

That circuit is more correct, unless there are other reasons, try to keep the circuit drawings in a conventional layout, (transitors and fets are normally presented vertical. )

NarWhale

4 years ago

Right on, thank you BillyT. Sadly, I haven't actually learned "conventional layout" so I will add this to my growing understanding of it.

NarWhale

4 years ago

Would this be considered more conventionally accurate?

BillyT

4 years ago

In most cases, try using semi conductors the way that they drop down.

NarWhale

4 years ago

Gotcha... this layout makes me happier anyway since all of the little magic balls are going around in harmony.

BillyT

4 years ago

http://everycircuit.com/circuit/6353228670959616

NarWhale

4 years ago

I didn't realize that I could target wires with the "view waveform" tools. Also, I now see that the the MOSFET drops in differently than I had it. As for your circuit, I like that the buttons are "outside" of the active circuit, but I thought I was supposed to have the power source in the upper left of the schematic whenever possible. If that is something I picked up that is outdated, I will edit that part of my brain.

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