# Is this a feasible circuit?

Hello everyone!
The last couple months I’ve been working on this project, I’m nearing its end and I’m getting really excited! However, this is still pretty new to me and so I was hoping my electrical diagram/accumulated knowledge could be verified before I go and start spending money on parts. All criticism is welcome as are any additional resources.

Logic:
Arduino setup:
Arduino pins (aside from the power section) at the bottom are capable of outputting up to 40mA at most and when using multiple pins, no more than 200 mA should ever be drawn at once

Piezo buzzers are the only electrical component that do not need resistors

This was taken directly from How To Mechatronics, attaching a 330 Ohm resistor to the LED strip lowers its electrical noise

The other resistor attached to the LED strip should be 25 ohms, seeing as I don’t have one though I will be using a 27-ohm resistor instead. Where 5 LED’s on the strip should take up 300mA (each GRB uses 20mA and I’m using 5 in total, therefore 20 x 3 x 5 = 300). Using Ohms law R = V/I, therefore R = 7.5/0.3, therefore R = 25.

**I would like to add that I also looked at Watt’s law and was a big confused as I got a current of 200 mA instead (as the LED’s each use between 0.1 – 0.3 Watts, therefore I = W/V, therefore I = 1.5/7.5, therefore I = 0.2) I went with the 27 ohms instead of the 37.5 ohms watts law gave me instead because How To Mechatronics really seemed to know what was up

I chose to power the board via the 7.5V, 1A adapter mostly because I wanted its voltage-in to be regulated and seeing as it won’t be plugged into a computer, I thought USB was a bit sketch and it made more sense to use the power port as opposed to the Vin pin.

Motor setup:

The motor was chosen based off of my need for high torque – the door handle I am trying to push requires 5 pounds (raised to 6 pounds for extra breathing room) and the entire handle is 4.5 inches (lowered to 3 inches for breathing room) in length (the measurements were provided by a friend as I wont be home for a little bit, might seem a bit overkill but its just cause I don’t think they are entirely accurate in the first place). Using these measurements and the equation Torque = length x Force I got the required torque had to be greater than 0.3572kg/cm to open my door. Knowing this I took a look at a bunch of Nema stepper motors and chose one capable of producing that torque (based off of its holding torque) that was the lightest and smallest. I wanted something light as I am still unsure how I will be mounting this to my door…

Originally, I was going to use the L298N but seeing as how using the 5V pin off the Arduino is not recommended for powering it and that they generally don’t dissipate heat that well for their motors I decided not to

Lastly, the 12V 4A power supply was chosen because I needed something stronger than 9V and I wanted to save money. Seeing as I would have the 0.5A - 0.7A current option selected (to my knowledge anything more could cause damage unlike with the Arduino, extra current is not necessarily a bad thing in this case) it’s a bit overkill. I’m thinking it shouldn’t cause any thermal limiting though seeing as it is rated to 4A and its not as if my motor will be going that often anyways

Links to components (all links except for the motor which goes to pololu resolve to amazon):

7.5V 1A Power supply:

12V 4A power supply:

KEYESTUDIO W5500 Ethernet Arduino (Uno):

NEMA 14 stepper motor (2.7V, 1 A/Phase):

TB6600 stepper motor driver:

LED strip (WS2812B):

Passive buzzer:

Ethernet cable:

LED strips do not use or need that 27 ohm resistor. Supply 5 volts at sufficient amperage capacity directly to the v+ of the strip.

The 330 or sometimes you see 470 is to protect you (your strip, that is) in case you do one of a few dumb things that can be. Done.

a7

The LED strip you link to says it is 18W total @5V....Arduino 5v regulator is not made to handle current that high.
You will need another power source, perhaps the 12v from your motor driver and drop down to 5v through an appropriately sized down converter or similar.
Switch the LED's via a mosfet say IRFZ44 or similar with gate connected to your pin 12 (I assume is the switch)

alto777:
The 330 or sometimes you see 470 is to protect you (your strip, that is) in case you do one of a few dumb things that can be. Done.

No, the resistor in the data line to the first WS chip is for noise reduction (AKA ringing of the PWM signal).

But, OP, you cannot power the LED strip from the Arduino 5V pin.

Is that just a piezo element in the buzzer ? I suggest a resistor of 120 Ω to that buzzer for safety. A piezo element behaves as a capacitor and the current peaks might be too much for the Arduino.

The 40 mA is the shortcut current for an Arduino Uno. The rule of thumb is to use a maximum of 20 mA.

The ledstrip controls the current to the leds. They need to be powered with 5V (without resistor). You use HowToMechanics as an example and they don't use that 27 Ω resistor: How To Control WS2812B Individually Addressable LEDs using Arduino.

The 330 Ω is good, but I had no trouble without it.

You can buy a 5V power supply for the leds, or use a single 12V power supply for everything.
It is only 5 leds, so with a 1A DC/DC-converter, you can make 5V out of 12V.
I suggest to buy a good quality DC/DC-converter, you can find them at Pololu.

It is possible to power the Arduino board via its 5V pin. When applying a very strong 5V to the 5V pin at once, then the onboard voltage regulator might blow. It is okay if that 5V is not very strong and not applied at once. The current from the 5V might run into the USB cable and into your computer. This can damage your computer. I did not look at the schematics of the board, but there should be a polyfuse. If that 5V is not too strong, your computer will be okay.

A safer way is a USB plug with 5V. Then you plug in either the 5V from the DC/DC-converter or a USB cable to the computer.

An alternative for that Arduino board with Ethernet is a ESP32 board with Wifi. When connecting a ESP32 to a 5V ledstrip, you have to amplify the 3.3v data-signal to a 5V data-signal for the ledstrip.
The Ethernet library might have trouble with sockets that are not closed. The ESP32 has Wifi with higher level functions and will be more reliable.

Koepel:
The 330 Ω is good, but I had no trouble without it.

If your wire to the first LED is short, less than 1 meter, then the series resistor is not needed. Longer cables add capacitance and the series resistor makes a passive low-pass filter.

The series resistor, whatever it does for reflections and spikes and signal integrity, also protects from the damages that might occur if one were to hook up ground and connect the DI pin to V+. The rumor is that the protection circuitry normally found on inputs is somewhat under designed.

Which we can imagine happening many ways, like plugging in a strip to a live circuit in a clumsy matter.

So there's still a reason to use that resistor.

I've done about 1/2 the time just randomly according to mood. I have not had a problem without it. I pay some attention to lead dress. The strips are usually right there next to the processor.

a7

alto777:
LED strips do not use or need that 27 ohm resistor. Supply 5 volts at sufficient amperage capacity directly to the v+ of the strip.

The 330 or sometimes you see 470 is to protect you (your strip, that is) in case you do one of a few dumb things that can be. Done.

a7

Thank you so much!

bluejets:
The LED strip you link to says it is 18W total @5V....Arduino 5v regulator is not made to handle current that high.
You will need another power source, perhaps the 12v from your motor driver and drop down to 5v through an appropriately sized down converter or similar.
Switch the LED's via a mosfet say IRFZ44 or similar with gate connected to your pin 12 (I assume is the switch)

Thank you for taking the time to read it, I even learned how to read/write diagrams for this post to make it simpler but yeah no it was a lot so I really appreciate you taking your time to respond
With regardes to the 5V pin, I do not believe it actually goes through the regulator, this is because inputting Vin is not recommended through it via the L298N motor driver logic output (stated its not a regulated pin on the Arduino site) but also cause of this video I watched a while back https://youtu.be/mTHwa_UCYMQ?t=558
Either way I now have an idea about how to drop V in a circuit so thank you for that

Koepel:
Is that just a piezo element in the buzzer ? I suggest a resistor of 120 Ω to that buzzer for safety. A piezo element behaves as a capacitor and the current peaks might be too much for the Arduino.

The 40 mA is the shortcut current for an Arduino Uno. The rule of thumb is to use a maximum of 20 mA.

The ledstrip controls the current to the leds. They need to be powered with 5V (without resistor). You use HowToMechanics as an example and they don't use that 27 Ω resistor: How To Control WS2812B Individually Addressable LEDs using Arduino.

The 330 Ω is good, but I had no trouble without it.

You can buy a 5V power supply for the leds, or use a single 12V power supply for everything.
It is only 5 leds, so with a 1A DC/DC-converter, you can make 5V out of 12V.
I suggest to buy a good quality DC/DC-converter, you can find them at Pololu.

It is possible to power the Arduino board via its 5V pin. When applying a very strong 5V to the 5V pin at once, then the onboard voltage regulator might blow. It is okay if that 5V is not very strong and not applied at once. The current from the 5V might run into the USB cable and into your computer. This can damage your computer. I did not look at the schematics of the board, but there should be a polyfuse. If that 5V is not too strong, your computer will be okay.

A safer way is a USB plug with 5V. Then you plug in either the 5V from the DC/DC-converter or a USB cable to the computer.

An alternative for that Arduino board with Ethernet is a ESP32 board with Wifi. When connecting a ESP32 to a 5V ledstrip, you have to amplify the 3.3v data-signal to a 5V data-signal for the ledstrip.
The Ethernet library might have trouble with sockets that are not closed. The ESP32 has Wifi with higher level functions and will be more reliable.

It is a piezo, ok I'm definately wanting to error on the side of caution so I will for sure use it! Thank you! Also yeah the resistor was just me being dumb haha I thought cause it was only 5 LED's being used that I would need one in comparison to the video
I will be swapping to a micro USB port power supply for sure now so the arduino should be reciveing 5V at max for everything, I deffinately want the electricity to be regulated Im hoping it lasts a while haha
Also thank you I hadnt heard of the ESP32, I'll look into it Thank you so much I really appreciate your feedback

alto777:
The series resistor, whatever it does for reflections and spikes and signal integrity, also protects from the damages that might occur if one were to hook up ground and connect the DI pin to V+. The rumor is that the protection circuitry normally found on inputs is somewhat under designed.

Which we can imagine happening many ways, like plugging in a strip to a live circuit in a clumsy matter.

So there's still a reason to use that resistor.

I've done about 1/2 the time just randomly according to mood. I have not had a problem without it. I pay some attention to lead dress. The strips are usually right there next to the processor.

a7

Look at the data signal with and without the resistor.

dhw123:
With regardes to the 5V pin, I do not believe it actually goes through the regulator, this is because inputting Vin is not recommended through it via the L298N motor driver logic output (stated its not a regulated pin on the Arduino site) but also cause of this video I watched a while back https://youtu.be/mTHwa_UCYMQ?t=558
Either way I now have an idea about how to drop V in a circuit so thank you for that

Your diagram shows an input to the Arduino @7.5v and thr LEDs driven from the Arduino 5v out.
This 5v out comes through the regulator whether you like it or not.

dhw123:
I will be swapping to a micro USB port power supply for sure now so the arduino should be reciveing 5V at max for everything,

Do not use the USB port to carry the LED strip supply current, you are relying on the PCB of the, I assume, UNO to carry the current.
Although you will not be using the linear regulator on the UNO when you supply 5V, if you are supplying any external hardware with 5V, do it externally and not via the controller.

Does the motor just move a door handle to operate a door latch so that the door can be pushed open?
Did you consider an electric door strike?

Tom...