Considerations about Circuit

[viviantern]

Note: Can skip all images except last, which is a schematic created using the editor.

I am at a point in the design process where I have created a schematic of the circuit that I want to create. I am using a buck converter to step down a 24V DC battery to 5V and using that battery to power an arduino. This arduino is acting as a speed controller, using PWM and getting input from external switch to set the speed. The input from this switch will be programatically read to set the speed output. The 5V output signal from the arduino then gets run through an op-amp configured as a non-inverting amplifier and drives a motor. The schematic follows: []1

This is the first real circuit I have created, and I don't know where to go from here. It is more than likely that I have made a mistake somewhere or forgotten a part or some heat/power consideration, but I don't have the slightest idea (1) how I could check my circuit for those things or (2) how I would remedy them.

I was wondering how I could go about doing these things and improving my knowledge of electronics in this way. I apologize if this question is somewhat vague; however, I really respect this community and the years of experience you have in the field, and I was hoping that your insights would be valuable in this question, as I don't really know how I could make it more specific. Thanks.

EDIT 1: Ok, after suggestion I am replacing the op-amp with an n-channel MOSFET as follows (Edit 2: added a 10K pull-down resistor on the gate of the MOSFET):

EDIT 3: Added pull down resistor to schematic and flipped MOSFET:

EDIT 4: Adding a full schematic LM2678T-ADJ datasheet:http://www.kynix.com/uploadfiles/pdf2286/LM2678T-ADJ.pdf(Edit 5: switched NMOS and Motor position):

simulate this circuit – Schematic created using CircuitLab

[AustralianPyromaniac]

Sorry, what is this a schematic of? What are you making?

 

Unless I missed something.

 

Regards, AP

Edited December 15, 2017 by AustralianPyromaniac

[PeteyPyro]

Motor speed controller for a ball mill motor?

[AustralianPyromaniac]

Something for actively controlling the speed of a motor it does seem although what for I don't know. To create such a system for a mill is just overcomplicating things for no reason if that's the plan. Anyway, I'm sure we'll find out soon. In the mean time the suspense is killing me :-)

 

Regards, AP

[PeteyPyro]

I don't see a feedback loop for regulation nor a potentiometer for PWM/speed control. What am I missing? This seems a bit over engineered for what I'm thinking.

[OldMarine]

I didn't see a flux capacitor in there nor Dilithium crystals so I have no idea what it is.

[Baldor]

Forget the buck converter for only supplying an arduino. Just use a linear one, and put the arduino in low power as long as you can. Forget the arduino also, and the op-amp. Just use a 555 and a Mosfet.

[Richtee]

Well..I DID learn something. I had no clue what a “arduino” was

[MadMat]

Forget the buck converter for only supplying an arduino. Just use a linear one, and put the arduino in low power as long as you can. Forget the arduino also, and the op-amp. Just use a 555 and a Mosfet.

I agree, Pulse width, or duty cycle, is the way to go. The required circuitry is much more simple and reliable. Not to mention, you can switch out the mosfet with a GTO type triac and control ac motors as well. On to your question; when designing a circuit, once you get your calculations compete and have a schematic drawn, the next step would be to wire-up a prototype circuit on a solder-less breadboard. All the components and wires simply plug in on this kind of board, so, if you run into any unexpected problems. it is very easy to make changes.

Edited December 27, 2017 by MadMat

[starxplor]

I am disappointed it took three pages of results for 'bread board' to get to this:

 

As for the arduino, sometimes it is just more fun AND educational to learn to program one?

[shenghuo]

thank you so much for sharing it, it's really good, I found the LM2678T-ADJ on Jotrin Electronics Limited. Can you recommend some other electronic onlineshops for me to choose from? thank you in advance.