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# DC Motor with variable speed project

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#### CharlN

##### Newbie level 2
Good morning geniuses!
I am new to electronics and new to this forum, so please excuse my lack of knowledge.
I want to assemble a variable speed DC motor and DC power source, and would really appreciate your thoughts about the logic, which components to use and how to put them all together. I have very little experience in electronics so it’s probably safer to buy the different ready-made components and just connect them all together (if possible).

1) Power Source:
- 3x 18650 rechargeable batteries
- Charge port
- Housed in a covered sled or housing
- Not sure if a BMS is needed?

2) Voltage Selector:
The motor needs to operate at 2 speeds (slow and fast), so my thinking is that by using a step-down type voltage regulator I can have a switch for 12V or 6V, giving me the fast and slow speed selection. Whichever voltage is selected, will then feed the PWM speed controller, to give the variable speed (0-100%) of the selected voltage, for more precise control of the motor speed. If my logic is correct (and that’s a stretch!), for a motor with max speed of 2,000rpm @ 12V, by feeding it with 6V the max speed will be 1,000rpm @ 6V. Thus by selecting 6V, the PWM speed controller will then allow me to regulate 0-100% of 1,000rpm?

3) PWM Speed Controller:
- Dial for 0-100%
- Switch for FWD (CW) or REV (CCW)
- Soft start and immediate stop
- Ability to add in a foot pedal potentiometer at a later stage (if required)

4) DC Motor
- Brushed (for simplicity and cost) and preferably not geared (for longevity and noise)
- Max speed of somewhere around 1,500 - 2,500rpm @ 12V
- CW and CCW rotation
- Not much torque required
- No more than +-2-3A max
- 755 type or smaller

Do you think this will work, and if so, which components would I need and how to connect them? Oh and the budget is not more than $100-$150 max.

#### d123

Hi,

Hard to say. In principle - yes it could work. Maybe show what you think might work - real parts and modules, that makes it easier for someone to offer meaningful advice and suggestions.

Maybe draw a block diagram of how these parts and modules interact with their connections. Then, referring to their specifications, look at ins and outs to see if they fit together or need additional parts. Think about what needs to be quiet and what will be noisy and if that will be a problem or is dealt with by the modules.

#### CharlN

##### Newbie level 2
Thank you for the suggestion d123, I’m not sure I could draw a block diagram because I have never done this and really don’t have a clue &#55357;&#56854;
But perhaps I can shop around for the components I think might work and post them here.

#### d123

Hi,

Yes, that's a good idea. Look for the parts and post them here, then it's easier to develop your idea.

A block diagram isn't so hard. Squares/Rectangles and lines/arrows joining them, showing how they interact, e.g.

Power source(s) for recharging->battery pack->step-down/voltage selector switch->PWM controller->motor

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