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Considerations about Circuit

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#1 viviantern

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Posted 15 December 2017 - 01:42 AM

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: [76t2e.jpg]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):0dLFv.jpg

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

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

dLO0v.png

simulate this circuit – Schematic created using CircuitLab



#2 AustralianPyromaniac

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Posted 15 December 2017 - 01:52 AM

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

Unless I missed something.

Regards, AP

Edited by AustralianPyromaniac, 15 December 2017 - 01:56 AM.

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#3 PeteyPyro

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Posted 15 December 2017 - 06:30 AM

Motor speed controller for a ball mill motor?
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Pyrotechnician. It's not an ocupation. It's a diagnosis. Please WEAR YOUR PPE!!!

#4 AustralianPyromaniac

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Posted 15 December 2017 - 07:44 AM

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
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#5 PeteyPyro

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Posted 15 December 2017 - 09:24 AM

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.
Pyrotechnician. It's not an ocupation. It's a diagnosis. Please WEAR YOUR PPE!!!

#6 OldMarine

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Posted 15 December 2017 - 10:42 AM

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


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#7 Baldor

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Posted 16 December 2017 - 02:36 PM

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.



#8 Richtee

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Posted 17 December 2017 - 08:34 AM

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


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#9 MadMat

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Posted 27 December 2017 - 02:51 PM

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 by MadMat, 27 December 2017 - 02:58 PM.


#10 starxplor

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Posted 27 December 2017 - 10:40 PM

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

normal_bread_chopping_board_2_top_view.j

 

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


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