I am having an issue with a 12v power adapter as a massive drop in voltage occurs when a 12v motor is attached. The adapter must be unregulated as it reads about 14v with my multi meter when it is plugged in with no load. When I attach a 12v dc motor the motor makes a quarter turn every few seconds and the voltage at the leads drop from 0 to 1v.
The motor has a rated current of 0.32A and rated voltage of 12V. The AC to DC adapter's input is 100-120v and it's output is 12v, 1amp. Similar issue with a 5v adapter with a 5v dc motor (this adapter seems to be regulated though).
I have tried using a diode in series with capacitors on the breadboard as well as other configurations with the L298N, same results. Perhaps I am being stubborn and should get a transformer and attempt to create a rectifier but was hoping to get a better understanding of what is occurring. Any info or clues of where to look are much appreciated.
"12V" often means 13.8V as that is the voltage in a 12V automobile when the engine is running and the battery is fully charged.
It sounds like the inrush current (stall current) on the motor is too high for the power supply and it is shutting down due to overload.
Do you have a 12V battery to test with? I have sometimes used a weak power supply to charge a small battery and connected the circuit to the battery under charge. The battery supplies peaks while the power supply is topping up the battery during the troughs. But I only did this while I was waiting for a new power supply to arrive.
The '12V' output specification on various power sources (eg. car batteries, some power supplies) is often misleading, and is/was quite normal for the no-load voltage to be higher than 12V. For example, some '12V DC' power sources might be 13.8 V (no load voltage) ----- although, some specifications really might indicate 13.8V DC.
A real power supply or voltage supply has some power losses --- which can be 'modeled' as a resistance or resistor. All you need to know is what the current is through the resistor (or an estimate of it). And this current not only flows through that model source resistance, but also flows through the load.
This means --- if the current that flows through the load is relatively large (even for a short period of time), then there is a formula (V = I.R) .... Ohm's law ... which allows you to estimate a voltage drop across that resistance at any particular time. In your case, you're measuring voltage across a wire or cable, which also has some resistance. So if you have a relatively large current that flows through the load, then you're going to measure a voltage (due to the current surge).
The thing is ... what current surge? That can happen with motors. If a motor is initially not moving, or unmoving, then enough force is required to get it moving ..... which is going to be related to getting enough current to move it. But once the motor is moving, the amount of current can then go down to some lower value. So the words 'motor starting current' might be relevant here.
So, depending on how much starting current is required, you probably need a more substantial power supply ..... a more hefty one, that can handle more power or current ..... to avoid hiccups or glitches.
I'll have to look into another supply after testing the motor with a 12v battery, however, with what you just stated above a 12v supply with a higher amperage should do the trick?
Crazy specs, make no sense. You are going to have to do some measurements.
Firstly you'll need an accurate (preferrably 4-wire) measurement of the motor winding resistance
when the rotor is held stationary.
This will tell you the stall current rating, and together with the basic size of the motor
enable a guess at the power rating (you'd expect about 85% to 90% efficiency for such
a motor at its continuous rated power, ie about 10 to 15% wasted as I-square-R heating
in the copper windings.)
Do you have a power supply with a configurable current limit? This makes measuring small
resistances easy.
Guessing from the size of the motor that 150W is a short term peak power rating, this looks like
the sort of motor used in cordless screwdrivers and drills, for which such a power rating is
believable.
The 0.32A figure is thus clearly complete nonsense. It might be a no-load current rating, but
its probably completely wrong.
