[Fritzing] Circuit help for buttons

Alright, so I've changed my circuit over to 3.3v instead of 5v. I've got it working with my 5v led strip with external power.

However, even with a 50-100ohm resistor - my two 3mm leds can only stay on so long before they stop being lit. Do I need a higher resistor? or have I reached the limit of 3.3v in some way?


Measure the voltage across the resistor when the LEDs are ON.
Use OHMS LAW to work out what the LED current is.

Usually if they fade it is because the current is too high and they are dying.

Tom... :smiley: :+1: :coffee: :australia:

Is the 3.3V coming from the 3.3V pin on the Nano? If so that may be the problem. The 3.3volt supply of a Nano is extracted from the USB<>Serial chip, and 30mA draw is about max.

Why switch to 3.3V?

Can you post a schematic of your circuit as it is now. No need for a fancy CAD generated schematic, photos of a hand drawn schematic are fine.

Alright, I'll give this a go and let you know tomorrow if it's solved.

I'll also add an active buzzer as I'm using the indicator buttons to also select/iterate through modes.

Mode 1) indicators
Mode 2) change led colour (hue)

Initially I tried hooking up a power supply to the 3v3 pin to power the arduino. However nothing happened. So I connected it to the 5v and it worked perfectly. Maybe the 3v3 pin does something different?

I'm only connecting a digitan pin to the data pin of the led strip. I don't believe it has much power draw at all. The entire arduino is using 9ma @ 3.3v when controlling the lights. 2ma when it goes into deepsleep mode.

I switched to 3.3v for a few reasons. It uses less power, the active buzzer I have is 3v, it's able to interact with a sim/gps module as it supports 4.5v max (in the future), and now that I'll be using a mosfet - I don't need 5v like for the reed?

I'm very bewildered why the aduino uses less power at 5v. It's like 25ma 5v vs 8ma 3.3v (without lights)

I'll work on a schematic. Hopefully you guys aren't too nit picky.

Pls clarify the voltage and where it is coming from** :

  1. Arduino
  2. LEDs

** i.e. external power supply, a pin on the arduino etc.

Arduino power supply is from a step down buck, it'll be either a 12v to 3.3v or 72v to 3.3v. I'll probably start with the first and switch to the second so it can draw power when it's off.

The LEDs are powered from a USB pack. I noticed it draws quite a bit of power, even when the LEDs are off. Presumably because each can be individually controlled. I'd need something like a mosfet, except something which doesn't draw power in the on/off state - only when switching.

No problem. If you make serious blunders, I won't tell you about them. Nah. Seriously what is wrong with constructive criticism that might lead to some improvement?

What is "it" that draws power? You've already built the MOSFET circuit? It should not be drawing any power. How do you know that power is being drawn?

You didn't apply 5V to the Vin pin did you? That is out of the published Arduino specifications. If you want to apply 5V, apply it to the 5V pin.

Obviously there are big problems in your circuit, so don't waste your time posting until you can produce a diagram.

Just to be sure, pls verify the Mosfet Drain is connected to the Arduino ground.

Mosfets when off draw power so low you will not be able to measure it (literally).

Trouble driving Mosfets with an Arduino are usually trying to turn the Mosfet's on, never been an issue driving it off.

CAUTION: I'm not sure where you will be getting your 72V, however buck converters do not isolate grounds so the 72v ground = Arduino ground = Mosfet/LED ground.

Need to be careful about the 72 volt power an how it is created.

I haven't bought the MOSFET's locally yet. I'm still busy working on getting everything else working perfectly.

Don't MOSFET's consume electricity to keep the gate open when they're on?

It's 60v as that's what the battery runs at, but I'm considering 72v for other scooter models.

Is the concern with non-isolated grounds that a shortcircuit might fry everything? Hmm, I'm initially sticking with the scooters 12v converter - it just means it's only on when the scooter is on and the cable out is from the headlight. (as there's no always active 12v connector)

I didn't realize it was a scooter. Had it been some industrial device one often doesn't know the ground path.

You are fine with a non-Isolated stepdown, but sure to add a fuse as close to the battery as practical

Only a few nanoamperes. We all got pretty excited when they came along.

Roger that.

What kind of fuse is recommended? I have a car blade fuse holder, car ANL, holder, glass fuses. It's really not going to draw more than 20 ma at 3.3v, although if I add the GPS/SIM module - I believe this can reach 60+ ma

So for my indicators, I was going to use mosfets as it's going to blink and normally be off.

I wasn't sure if they'd be suited to the LED strip lights which are commonly both on and off for long periods.

If so, I may need 3. I cannot find any multiple MOSFET gate IC, not sure if such a thing exists.

Here's a video of where I'm at. I've finished the software side for now.

Hi ground, thank you for all your help.

I've put together a schematic. I will update the missing ohm resistors when I figure out the correct values for the LEDs, although they are a placeholder for the mosfet relays.

I used EasyEDA to put it together.
Schematic_Light System V1_2021-11-25

Editable Schematic:

Arduino Source Code:

I'll try add the mosfet to the schematic. I've never made a circuit board, written a schematic or used an arduino before. So without your help, I would've never made it this far.