A message from our CEO about the future of Stack Overflow and Stack Exchange. Read now.

Hot answers tagged

7

It's really simple. They have one fixed power level, and turn it on and off. You can hear it when it is on low power. It'll hum louder for a few seconds, then have a longer period when it is a little quieter. On is louder, off is quieter. On full power, it is on all the time. Lower power switches it off for a short pause with a longer on period. Low ...


4

If you begin with an analogue sine wave (basically an oscillator like a Colpitts or phase shift type), you can adjust it's amplitude to 1 volt peak to peak and feed it into an LTC6992. Pulse Width Modulation (PWM) Controlled by Simple 0V to 1V Analog Input The LTC®6992 is a silicon oscillator with an easy-to-use analog voltage-controlled ...


4

How to measure the voltage drop across the diodes D102 and D103 in this senario? Like you did: with an oscilloscoop. For example by measuring the anode of the diode on one channel and the cathode on the other channel and use the math functionality (if exist) to calculate the difference, or use the cursor to measure the difference. Another option would be to ...


4

How to measure the voltage drop across the diodes D102 and D103 in this senario? You have already done this with scopemeter. This is the correct way. Why am I getting a PWM voltage waveform only the cathode of the diode and not at the anode? Because you are not switching the source. And since the current flows through the diode, you'll see the pwm-like ...


3

Add a CMOS logic gate after the optocoupler/R2. That will buffer the output and the voltage will be more accurate and the time constant will be the same for on vs. off. split R4+R3 approximately evenly (11K-ish) and put the capacitor to IRET in the middle. You're not really filtering the current input well by putting the capacitor where it is. The time ...


3

No. You cannot calculate the speed based on the duty cycle. The duty cycle dictates the average power supplied to the motor, and although this is proportional to motor speed for certain regions of operation, no direct relationship exists in all cases. The speed at a given power will depend on the load. This is why a tiny motor whips round at no load and ...


2

Get two identical batteries. Power the audio amplifier with one battery, and your complete LED circuit with the other battery. Make sure both circuits are completely disconnected (including ground). Got noise? You have magnetic or electrostatic field coupling. This is a layout issue, for example a high current wire for a LED runs close to a wire carrying ...


2

How to measure the voltage drop across the diodes D102 and D103 in this scenario? On a DSO with 2 probes use CALC Ch A-B Why am I getting a PWM voltage waveform only the cathode of the diode and not at the anode? Anode is connected to a voltage source which in theory is a 0 Ohm to AC but Cathode is high impedance. Why is there a 0.3V ...


2

Most microwave ovens use the on-off method of control described in other answers. There are microwave ovens advertised as "inverter" products that rectify the incoming power to DC and then invert it to AC at a high frequency. That allows the use of a smaller transformer to boost the voltage to the 2000 volts or so required by the magnetron. The inverter can ...


1

Most, if not all microwave ovens, use the method 1. At full power it is always on, and at lower levels, it is just turned off for a period of time. The starting and stopping can usually be heard when observing the device operation.


1

You should use a microcontroller with 'fancy' PWM. This problem is almost purpose built for an inexpensive microcontroller because of the extent to which it needs to be customized (relationship between DC input to AC output frequency and amplitude, output filter configuration, bandwidth...). You can get a microcontroller for less than $1 with an ADC input ...


1

The problem is that the optocouipler current must flow from the vreg of the controller. 5V into 2.3K is about 2mA. that current is comiing from the 4-20mA loop - so there's your minimum 2mA to fix: Swap the opto-coupler output and R2 This will invert the sense of the optocoupler, so that when the optocoupler is off it calls for less current in the loop, ...


1

There should be a drop of about 0.7V across those diodes, when there is nonnegligible current through them. When Q100 is on and you have a load connected, it should be down at about 7.3V. In a perfect world, there would be no drop across the diodes when Q100 is off. However, a little bit of extrapolation on the curves indicates that a current of 1-10uA ...


1

You made a few errors in your code: ESC.attach(9,100,2000); should be ESC.attach(9,1000,2000);, so, 1000 instead of 100. and potValue = map(potValue, 0, 1023, 1000, 2000); should be potValue = map(potValue, 0, 1023, 0, 180); because the next line, the command writeMicroseconds(angle) only accepts a value to write to the servo, from 0 to 180 Have a look ...


1

The turn on overshoot without feedback depends on how much losses you allow in the FET (RdsOn) as L/R ratio affects Q or inverse damping factor. Simulation with 4 sliders


1

switching the ULN2003's GND (Pin 8)with a transistor at 1KHz. No,that will not work. At the moment that you 'switch' the ground off you have lost the reference against which the inputs switch. In other words: your whole ULN2003 is floating and you have no idea how the inputs will react to that, but my educated guess is bad. Much better if you would ...


1

If the PWM is being applied to to the motor properly (current recirculated through the motor during PWM 'off' period, and frequency high enough to smooth current via the winding inductance) then the speed of a permanent magnet DC motor should be proportional to the PWM ratio. PWM creates an average voltage equal to the supply voltage multiplied by the PWM ...


Only top voted, non community-wiki answers of a minimum length are eligible