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This is my theoretical (haven't tested yet) circuit I have designed for a project of mine. Electrics is a new field for me so please raise flags if my circuit has flaws.

Assuming the circuit is fine, the question I now have relates to component protection and noise. What is the best way to protect the MC and the motor Driver from potential back-EMF?

What size capacitor should be used over each DC?

Will the noise from the DC motors effect the circuit? if so, what can be done?

Anything else that should be done, please let me know. thanks enter image description here

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  • \$\begingroup\$ I think many of your questions hinge on the motor driver design. Is this an off the shelf or self-built unit? Either way, it and the microcontroller interfacing are the details needed before really helpful answers can be given. \$\endgroup\$ – user65586 Mar 31 '16 at 13:14
  • \$\begingroup\$ thanks, so yes it is a off the shelf MOSFET driver. Here are it's details, link \$\endgroup\$ – KiwiOnTheShore Mar 31 '16 at 22:13
  • \$\begingroup\$ Also I would like to use the energy restore capability of the driver as this system is being used of a electric vehicle, where a substantial amount of back-EMF will occur. Interms of the MC, I'm simply using an arduino that receives its step down power from the buck converter, details link \$\endgroup\$ – KiwiOnTheShore Mar 31 '16 at 22:24
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Diodes will protect your driver and MC from back EMF. Your driver has 30Amp peak and 10Amp rated, and your motors require 8+2.5=10.5 Amp, maybe it is not necessary to place output capacitors, but I would place some value around 47uF for starting (depending of what kind of output you have). Try to connect GND from motors close to the battery input (to define path to the circuit wide from driver and MCU as much as possible).

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Think about using Solid State Relays. They would give you the isolation and protection you need. This would be a perfect application for them. You can then upgrade the motors to 120V too. Also, adding varistors between the Driver and the motors would give the protection you need for the Driver, whatever that is. (Varistors are used in surge protection power strips)

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  • \$\begingroup\$ The motor driver probably already has relays or MOSFETs or something. And puzzled why a battery driven design would want 120V? \$\endgroup\$ – user65586 Mar 31 '16 at 13:12
  • \$\begingroup\$ Do you see any relays or MOSFETs in the diagram? If there were relays between the motors and whatever the Driver is , they would provide the protection. \$\endgroup\$ – Tim Spriggs Mar 31 '16 at 13:14
  • \$\begingroup\$ No, but a block diagram shows a black box device that could be powered by hamsters for all we know. If it is an off the shelf unit, then chances are it has relays or MOSFETs. The fact is that we don't know what this unit does, so suggesting "use relays" isn't actually helpful. It may already have relays on it. \$\endgroup\$ – user65586 Mar 31 '16 at 13:16
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    \$\begingroup\$ @TimSpriggs: This answer leaves a lot to be desired. (1) You don't put SSRs between a motor controller and the motor. (2) How would adding SSRs allow use of 120 V motors from a 24 V battery. (3) Normal protection diodes will provide much better protection than varistors on a low-voltage DC circuit. (4) Your comment that "relays ... would provide the protection" doesn't make sense either. Can you elaborate each in your answer explaining why you think they're good answers? \$\endgroup\$ – Transistor Mar 31 '16 at 13:52
  • \$\begingroup\$ If you notice it was just a suggestion (in order to upgrade to AC) but if you notice the varistor is the actual answer. Pardon me for any confusion. They make varistors for DC low voltage too. \$\endgroup\$ – Tim Spriggs Mar 31 '16 at 13:56
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A pair of diodes can hold the back emf between the rails. I googled for "back emf protection circuit", selected images, and quickly got a diagram of a circuit using diodes to clamp back emf to the rails. Such as:

enter image description here

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    \$\begingroup\$ I know the OP hasn't given a part number for the motor control board but it's very unlikely that clamping diodes have been omitted from it. i.e., They will be there already. \$\endgroup\$ – Transistor Mar 31 '16 at 15:38

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