Are there any changes needed in this circuit?

Hello guys.

I'm making a simple circuit and not sure what components are further needed to complete it.

I've hooked up 9 3W leds in parallel, and they blink for 2000 microseconds(it's a pretty short time and it only needs to blink about once in a minute so I guess I don't need to attach heatsinks on the LEDs.) when a projectile flies between the phototransistors. In this diagram, I couldn't find any proper phototransistor icons, so I just substituded them with led signs.

The LEDs don't need any more resistors, since the datasheet recommends voltages from 3V to 5V. And I also already tested the phototransistors and they worked out beautifully.

the problem is, the battery connected to the battery charging module(TP4056) has a pretty high discharge rate of 65C, because it needs to give enough current in a very short amount of time to the leds. 3W * 9 = 27W so the leds in total eat up 9A of current so I decided to use a battery capable of giving the leds enough current to light up properly. The battery is originally used to power small flying drones.

and now I'm afraid the over powered battery could somehow do serious damage to the mosfet hooked up to the led, or further damage the whole circuit including the microcontroller.

Are there any suggestions on adding any more electrical parts to the circuit? (Capacitors, Diodes, etc...) or is this circuit a good-to-go?

Receive and Transmit LEDs are grounded out.

Pin 3 is grounded.

The battery is not ground referenced.

U1 has no ground reference.

The MOSFET is backwards/not wired correctly.

No power to the Pro Mini.

LEDs in parallel are a no-no, LEDs need current limiting.


It’s simply all wrong.
:frowning:

Why is out+ and out- going to RXI and TXO of the Pro Mini ?

Oops. My bad. It's 4am in Korea and I think I'm not seeing things correctly. :cry:

I corrected the circuit, but couldn't find a solution on how to hook up the leds correctly. (LEDs in parallel are a no-no, LEDs need current limiting.) Should I hook them up in series?

Also, I just replaced the sensors with a simple push button.


Here is a quick photo I picked up on google. Will option A be a proper way to equally distribute currents? (A and B are the same circuit.)

What is the MosFET doing and why do you need three LEDS?

Indeed, but option B is usually more practical. :grin:

The leds consume a lot of currents. Each spend 3W so I need to control them with a mosfet.

Also, I only placed 3 leds on the schematics instead of 9, because I was too lasy to hook up 6 more

Resistor before led. Got it!

But WHY do you need so many LEDs?
And, if the MOSFET is supposed to control the LEDs, it's wired completely wrong.

IRFZ44N is not a logic level MOSFET.

Hmm. Can you give me any suggestions on how to do the wiring? Should I hook up resistors on each led?

Yes. I thought it was a bit much overspec MOSFET to use in a project like this. But is it all right to use mosfets instead of fets, since it draws a lot of currents?

But WHY do you need so many LEDs?

We don't know what you are trying to do. Everything in your first drawing is wrong and the MOSFET in your second drawing does nothing.

Care to explain what that gobbledegook is supposed to mean? :face_with_raised_eyebrow:

This link will show you how to wire a MOSFET as a low-side switch. You need to understand how to recognize the gate, source and drain of a MOSFET symbol.

https://electronics.stackexchange.com/questions/188745/high-side-driver-and-low-side-driver

You must pick a logic level MOSFET if you want it to work from 5V gate drive.

Thanks for the link sir. I guess I'll have to go back to the beginning and learn the basics

Sorry sir. I'll try to improve the circuit based on the comment suggestions and reupload it this weekend.

Forget about resistors when using 3W leds. You'll be battling thermal and efficucency issues you don't want/need especially if batteries are involved.
How are you going to cool those 3W leds? Are they already mounted on a heatsink?