# Tag Info

19

"Partially cloudy sky" and especially "Indoor light" are not a good recipe of testing a PV module. It may sound somewhat surprizing, but human eyes are not very good at estimating a total amount of light even to an order of magnitude. In a sunny day one may get as much as 1 kW of light per sq. meter. Clouds may lower it to as low as 10W ...

3

I have found that feed-forward compensation works well for brushed motors. It can maintain fairly constant speed, even at slow RPM. From your motor specs, stall current is 17A, with 12V supply. This spec suggests that winding resistance plus brush resistance is $12V\over 17A$ or 0.7 ohms. A compensating resistance of -0.7 ohms is required for feed-forward ...

3

But with no losses in efficiency this angular velocity should remain constant, right? No. Efficiency and speed relation to voltage are not the same thing. Let's consider an ideal DC motor wound with superconducting wire, with a wound field, that can be either in series with or parallel to the armature, driving a load torque, or twice that load torque. The ...

3

Yes your analysis is correct. In a 100% efficient motor the output speed would not change with load applied. As you varied the torque the current pulled from the electrical supply would change in direct proportion to the torque to maintain the relationship Pmech = Pelec. You can actually see from this how an real motor works, because the above statement ...

3

PV's and motor's both have an impedance. Z(PV) = Voc/Isc Motor Z(RPM) = 2)DCR + L * RPM* 2pi * 3600// mechanical load. Is much lower. What did you compute? energy? Or power or impedance ratio? Measure 1) & 2) What did you measure? Where are your specs !! Try full sun or bright 4W LED up close

3

One of the motors is connected differently to three phase mains so it runs in different direction. Some 3 phase mains plugs contain a switch to swap 2 phases to change direction of motors.

3

As a general rule of thumb: there is always a transition between "on" and "off". For your solar cell that means: no light -> no voltage , a lot of light -> maximum voltage, maximum current. You can try this yourself, if you equip yourself with a cheap multimeter and use this as a replacement to the motor in both: current mode and ...

2

That's the stator from a 'universal' motor. As you've already identified that the windings are 'working', you have already found which pairs of wires go together. The simplest way to get this object to generate for you is to spin a permanent magnet between the poles. The magnet poles should be aligned N to one pole piece, S to the other pole piece, and spun ...

2

The PPR number gives the number of pulses for a full rotation. But every pulse has two edges, or signal change. So if you monitor only the rising edge, you will count exactly PPR events in a full rotation. Every pulse has also a falling edge: it is "electrically" necessary in order to generate a subsequent rising edge. And you can monitor it too, ...

2

If you are measuring voltage at the brushes, the problem is most likely lack of good contact between the brushes and the commutator. If it is a minor problem, turning the rotor by hand and trying to run with a different starting position will likely get the motor running and prove that is the problem. You will still need to clean up the commutator and ...

2

It's a universal motor, disconnect it from the power then measure the bits that should conduct to see if they do conduct.

2

When the motor is not turning the current is maximum, because there's no back-EMF to oppose the terminal voltage. All of the energy going into the motor is burnt up in the winding resistance. As seen in your graph, when the torque * RPM is at its maximum, that's exactly when the power output is maximum. At that point, the motor is roughly 50% efficient -- ...

2

Power = Torque * RPM The plot of RPM is not shown but would be a positive linear slope. (X=Y) The plot of Torque due to back EMF is a negative linear slope. The product of the two linear opposing linear slopes starts at zero and ends in zero with a parabolic shape in between.

2

The relative permeability of air is about 1.0000004. A stream of air will decrease air pressure (Bernoulli principle) and thus slightly lower the relative permeability. But clearly this can only change within the range of 1.0000004 to 1 (vacuum) which is a change that is likely not detectable.

1

I hate these graphs. People look at them and think that they are operational graphs of the motor or something. But they are not. These graphs cover the full range from stalled rotor to overload up to no-load. It is assumed, but not always stated, that the voltage is held fixed. In this case, the input voltage is held at 12 V. Also, understand that the power ...

1

Unless the number of magnets is changed, the base speed can be changed only by changing the base frequency and base voltage. That would not change the available torque or the flux of the permanent magnets. The operating torque is determined by the load.

1

You can simply connect the two windings in series. You will need a strong permanent magnet that will fit in the opening without touching the sides, but as close to the sides as possible. North and south must be directed towards the sides, not the openings at the ends. The crank must hold the magnet tightly enough to keep it from sticking to the sides. Start ...

1

The comments have basically answered your question, but allow me to summarize. The L298N is an inadequate motor driver for this robot. It has a high voltage drop, and it's rated for only a few amps. Each motor on the robot can draw up to 6.6A at 7.2V, so ideally you should use a 20A motor driver for each side of the robot. Here's an example: RB-Dim-47 Your ...

1

I went to a local electronics shop and they tipped me off to these being transistors. Looking for "G1" transistors finally led me to the correct parts, specifically MMBT5551. I purchased these as replacements. They are SOT23 dimensions and their resistance was ~3.5MOhm. I gave the extra detail in my original post because I figured context would ...

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