Trouble building a controller for my 5V DC motor

Thread Starter

HerbertS

Joined Jan 16, 2024
3
Hello everyone! I'm currently working on building a controller for my 5V DC motor and could use some help with the challenges I'm facing. As a hobbyist in electronics with basic knowledge, I'm eager to learn and would greatly appreciate any assistance.

Here are the components I'm using:

  • 12V DC 2.5A power source
  • Resistors (220 ohms and 560 ohms)
  • Transistor (TIP122)
  • Diode (1N4007)
  • Capacitor (100nF)
  • Zener diode (6.8V)
I've attached a simulation image created in LTspice below. In the simulation, everything seems fine; the voltage at the emitter is 6.3V, and the representations of the motors have a decent 200mA current.

Real-life problems:

  1. In the simulation, I haven't connected a resistor between the collector and the source, but in real life, the 12V source beeps if left unconnected. This significantly reduces the current in the emitter, affecting the motors' performance.
  2. If I connect a resistor in parallel with the capacitor, my multimeter reads a 9V voltage. However, without the resistor, it drops to zero when I measure. The same happens when I connect my motor – zero current flows.
Could someone please provide guidance on what might be going wrong? I'm eager to understand these basic circuits to make progress.
 

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Thread Starter

HerbertS

Joined Jan 16, 2024
3
Hello! I have incorporated a potentiometer in the circuit between the motor and the power source, intending to control the motor's speed by adjusting the resistance. However, I've discovered that the motor fails to operate whether the potentiometer is included in the circuit or not.
 

BobTPH

Joined Jun 5, 2013
8,967
Well, if it is wired as in the schematic, the motor has no source of power connected to it, so I am not surprised it does not run.
 

crutschow

Joined Mar 14, 2008
34,452
I have incorporated a potentiometer in the circuit between the motor and the power source,
That's not how to do it.
The potentiometer will have to be a low value and dissipate a lot of power to control the motor speed.
You want use a pot to control the transistor output voltage which will then vary the motor's speed.
 

BobTPH

Joined Jun 5, 2013
8,967
Any use of a linear regulator or resistance to control a 5V motor from a 12V supply will waste more energy as heat than it will supply to the motor.
 

KeithWalker

Joined Jul 10, 2017
3,095
The most efficient way to control the speed of a small DC brushed motor is by using pulse width modulation. I suggest that you look it up. Here is a simple control circuit. The transistor may get hot if the motor draws too much current.

dcMOTOR.jpg
 

MisterBill2

Joined Jan 23, 2018
18,519
Staring from the beginning, just what "control" of the motor does the TS want?? Next question, does the TS understand the effects of resistance on current? Max has presented a circuit that can work but how much of it does the TS understand??
To provide useful help and good advice we need to understand what is needed.
 

KeithWalker

Joined Jul 10, 2017
3,095
Staring from the beginning, just what "control" of the motor does the TS want?? Next question, does the TS understand the effects of resistance on current? Max has presented a circuit that can work but how much of it does the TS understand??
To provide useful help and good advice we need to understand what is needed.
See post #3. The T.S. is trying to vary the speed of the motor.
 
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