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What's actually the voltage and ampere or watt marked on brushed DC motor meaning ? e.g. once found

12 V, 4 watt

would it be optimum or maximum voltage and one-third ampere, from watt, would it be starting, optimum or maximum ampere ? What is the maker company really to mean ?

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  • \$\begingroup\$ Anybody's guess. Most likely, rated voltage, and running current on its design load. Starting current will be much higher. Actual running current will depend on the actual load. \$\endgroup\$
    – user16324
    Jan 5, 2023 at 22:46
  • \$\begingroup\$ Ideally you shouldn't let it go above either of those values (might need a "slow start" circuit, for example) \$\endgroup\$
    – Ben Voigt
    Jan 5, 2023 at 22:46

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The voltage and current written on the motor can be called "nominal" or "nameplate" rating, and they tell you what conditions the designers intended the motor to run at, long-term. They're good for comparison purposes. You need about 4 watts of mechanical power and you are using 12 volts? Use this motor - it does what you need. Big ones are often rated in horsepower.

The actual voltage and current relate to the amount of speed and torque required. As you noted, a stalled or starting motor can take a lot of current (well above the nameplate current, which isn't a maximum limit); an unloaded motor can take very little current. If you give the motor less voltage it will be weaker and slower.

If you give it more voltage it will be stronger and faster - until it burns out. Any motor can burn out from overheating; the brushes in brushed motors can also wear out faster if the voltage is too high. If you make the voltage way too high you will be able to see flashing lights through the ventilation holes, caused by arcing - but the motor will still spin - for a while. On Youtube you can see people "upgrading" their 24V electric wheelchairs to 120V for funsies. It certainly works for long enough to make a video.


Motors aren't the only electronic components like this. Almost any component, even ICs, can be abused to a certain extent - as long as you're okay with voiding your warranty. Many hobbyists, prototypes and even commercial products do overdrive components beyond what the label says, or use them in weird ways. However, you're on your own, because (unless you're a very big customer with a lot of money) the manufacturer won't guarantee anything beyond what's written on the datasheet. So it's usually best to avoid it. At least if you stick to intended uses, you can point the finger at someone else if it doesn't work.

A capacitor and a backwards transistor without the base connected can make an oscillator. You bet the transistor manufacturer doesn't tell you what'll happen if you use it like this.

A different backwards transistor circuit can be used to generate white noise by amplifying the randomness of the individual electrons passing through the transistor.

Some CMOS NOT gate ICs, with some added negative feedback, can be made to hold in the middle between on and off, and act as an amplifier, as a small input "nudge" will cause the output to rocket towards being properly on or properly off.

Maybe someone else knows another interesting example in the comments.

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