# Tag Info

8

Your multimeter and your clamp meter are both not meant to observe PWM going through an inductive devices. You need an oscilloscope with a high-bandwidth method of sensing current. I don't know your PWM frequency, but rule of thumb: estimate how fast the transition from fully on to fully off has to be, take the inverse of that time (yielding a frequency), ...

6

They are for EMC - noise suppression, interference with radio transmissions. 0.1uF disc ceramics are commonly used, in a triangle (delta) - one from each brush to GND (the can) and one between the two brushes. Should have essentially no effect on PWM.

4

The Arduino's default PWM frequency is ~490 Hz. At this low frequency the motor probably won't have sufficient inductance to make the current continuous, so the rms current and voltage will be much higher than the average values that your meters read. I created a simulation in LTspice representing your situation, adjusting the motor's internal resistance, ...

4

You need to increase PWM frequency to at least a few kHz for the motor inductance to smooth out the PWM. Some types of motors have more inductance than others, so the optimum frequency will vary with motor type. Otherwise you will get large RMS current and corresponding large I^2*R losses in the motor, transistors and connecting wires. The BTS7960 is ...

4

Okay, the basic function of this circuit is as an oscillator. The frequency and the duty cycle both vary with the input voltage. Maximum frequency is at Vin = 2.5V where the duty cycle is 50%. I'm just stating that. The capacitor charges or discharges through R3 toward Vout of the comparator (which we can reasonably approximate with either 0V or 5V in this ...

3

It is caused by your eyes, because when the duty cycle is small (for example 20%) and you have a higher frequency (few kHz or more), the LED is on only for small amount of time. Your eyes can't take such high speed changes, so you sees it as a smaller brightness. The LED is actually as bright as it would be in long term on state. You have got 5V and a ...

3

The apparent brightness of a PWM driven LED to human visual system is a very logarithmic curve. It means you can easily see a big difference between PWM signals of 1%, 2% and 3%, but will not see hardly any difference at all between PWM signals of 97%, 98% and 99%. The average brightness of the LED to a light meter will still be linear in respect to the PWM ...

2

Usually Peltier are driven in current but whatever your manufacturer says… Unless you are using some kind of digital regulator, the standard is to trick its control loop influencing the feedback voltage. Good luck if the FB node is not available externally. In 99.9% of the regulators the voltage on the FB pin is compared with some constant value and the loop ...

2

As already mentioned, you want the PWM period to be much shorter than the L/R time constant of your DC motor to better approximate constant current for a given setpoint. I'll just add that the other side of the trade is that as you go to higher and higher PWM switching frequencies, your controller FETs (in your H-bridge) start dissipating more power because ...

2

The small B in the CH1 label below indicates that the BW limit is on. click on CH1 knob and select Bandwidth Limit Off The real signal will look more rectangular most likely. The bandwidth limit is offered by these scopes so you are not overly confused by the oscillations when not doing a proper differential measurement with low loop impedance return cable. ...

2

Your scope should be able to reproduce rise and fall times down to around 3.5ns. There is a relationship between the rise time of an edge and the signal bandwidth. The bandwidth of a square wave does not depend on the square wave frequency. It will always be higher than the frequency. The exact bandwidth in the signal will depend on the rise and fall time of ...

2

Figure 1. Original circuit. R1 is not wired as a potentiometer. It's wired as a variable resistor or 'rheostat'. If you move the wiper to the right the op-amp will see 5 V. If you move it to the left the op-amp will see $\frac {200k}{20k + 200k}5 = 4.55 \ \text V$. Meanwhile your op-amp has a gain of $1 + \frac {R_4}{R_3} = 1 + \frac 1 {3.7} = 1.27$ ...

2

PWM brightness control enables dimming of white LEDs without significantly changing their color temperature or CRI. It is however less efficient, and if done at lower frequencies, it can cause eye strain. PWM is also unsuitable for many video or photography applications. Current adjustment is more efficient and does not cause eye strain, but is more ...

2

You can use any microcontroller with 2 independent PWM interfaces. Program the hardware registers of the 2 interfaces in order to get the desired PWM period and Ton. The values that you will program in the registers will depend on the clock frequency that drives the PWM interface. Don't do it in software (delay loop). Use the hardware registers.

2

This is from some of the folks who make Kanthal wire. It goes into some detail about designing things with Kanthal heating wires and elements. At no point does it tell you how to calculate temperature from voltage and current or voltage and current from temperature because you can't do that. You have to have the ambient temperature. You have to have values ...

1

Current sensing is used to limit the output current to the voltage imposed by the error amplifier. If you force this to some predefined value you will still have output current given by the output voltage. It doesn't work as a current generator because if you'll change the load you'll get a different current, set by the voltage at the COMP pin. Therefore you ...

1

Low-side switching is easier to deal with using ordinary logic levels. High-side equivalents need a level shifter, be they FETs or BJTs. R2 is a pull-down to set the default state to ‘off’ when the MCU starts up but hasn’t yet configured the pin. No idea. Seems like it won’t work. If the cap were connected across Q1 collector / emitter that would work. I’...

1

As has been suggested, datasheets often not only explain how to use the chip but also offer example circuits. There are also websites that go into great detail on how to use the L293 such as All You Need to Know About L293D In any case, the L293D is a set of half-H bridges and there are some general concepts that are true for all half-H bridges. Think of a ...

1

I think you have slightly misunderstood the wiring schematic. Typically pin 8 and 16 are the main supplies that will be driving the motors. The PWM signal from the arduno will often be connected to pin 1 or pin 9, depending on witch H-bridge you are using TI's driver comes with a wiring schemattic you can use: https://www.ti.com/product/L293D

1

Edited after clarifications. This mode of operation is not so unusual for DC motors. Effectively, it is a buck converter, with the fixed side of the load attached to V-. Thus it shares some pecularities with the buck converter, such as discontinuous current mode operation (DCM). The difference is if you want to reverse direction. In your operation mode, you ...

1

So this is a dual MOSFET designed for battery protection, not really for general-purpose use because the drains are connected together internally. When PA4 or PA6 is high then 'R' and 'G' should show continuity to ground (they are connected together internally. When PA7 is high, then 'B' should show continuity to ground. If you were, say, to connect an LED ...

1

The 200000 cycles for a bulb likely has the implication of a thermal cycle per on off cycle, meaning the components heat up and cool down to increase wear. Good LED bulbs will also use a constant current driver rather than just a rectifier for better safety and efficiency, although you haven't linked a datasheet, my guess is Philips has the money to pay an ...

1

I quite sure that is measuring problem because if you loss power of 133W on driver, it totally melt down due to power converted to heat. Only reason for that is measuring tool can not average changing voltage or current to get correct value. I suggest to use RD low pass filter before measuring as shown. Note value for component just for example, you need to ...

1

Measure the current that the led draws without the R5 (with and without AINT0 connected). That's what I would do, if I were you, check what really is going on there,. I think it is more than "2mA drive strength" This 2mA must be the EK-TM4C123GXl pin's maximum value, which you should be taking care of (this means that the EK-TM4C123GXl can give ...

1

Will a higher order filter (Sallen-Key, Butterworth, etc.) work better than just a basic active RC filter? Yes it will. It'll be better because, as the "order" of the filter increases, the PWM switching artefacts seen on the output get progressively more reduced in amplitude: - Picture from here. So, in the above diagram you have a pass band ...

1

Additionally, depending on if you aren't concerned about cost, you can always add a buffer to help maintain signal integrity, this should protect the PWM from potentially being pulled to ground if its being attenuated significantly.

1

For a small motor my rule of thumb is to make the maximum pulse width of a given f and d.c. 10% of the L/DCR = Tau time constant. This puts it in continuous conduction mode (CCM) using the motor L as a RL low pass filter. However aliasing noises in the magnetics on different RPM frequencies of brush noise and switching frequency and if too low fSW then motor ...

1

You can use the following equations: $$\begin{bmatrix}V_a \\ V_b \\ V_c\end{bmatrix}=R_f \begin{bmatrix}I_{ag} \\ I_{bg} \\ I_{cg}\end{bmatrix}+L_f\dfrac{\mathrm{d}}{\mathrm{d}t} \begin{bmatrix}I_{ag} \\ I_{bg} \\ I_{cg}\end{bmatrix}+ \begin{bmatrix}V_{ax} \\ V_{bx} \\ V_{cx}\end{bmatrix}$$ where $V_{[a,b,c]x}$ are the voltages taken from the points ...

1

Since pwm from an MCU or an 555 IC is not used directly to the motor (a transistor/fet is placed between) it should not affect the pwm behavior. picture from here Various explanations can be found online like here The first and main reason is to reduce interference and noise. When the motor is in running condition, there is very frequently connect and ...

1

PWM (resolution and frequency) does influence the velocity accuracy via the torque production. velocity ripple is a form of acceleration (and deceleration) and this is influenced by the load inertia and torque. $T = J \alpha$ For a stabilized system where the load torque equals the torque production, there is no more acceleration and a steady velocity has ...

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