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Hello all.
I'll be giving an electrical engineering assessment test for a chemicals manufacturing company the day after tomorrow. The test will have sections on IQ, math, and engineering.
I was hoping that you all could provide sample recruitment tests that included questions of such a nature...
I apologize for not providing specifics. Yes, it's a power opamp: OPA549. And yes, the relay is a mechanical one and it is switching; it is fast enough to switch with the PWM (switching time of the relay is 5 ms whereas the period of the PWM is greater than 700 ms with a transitioning time of...
@FvM:
Thanks for the response.
I'm using this circuit for PWM generation:
An SPDT relay then monitors the High and Low of the PWM. If its High, the motor is connected to the PWM wave; if its low, the motor is connected to the secondary power source. I need to study the effect of the...
It seems I had misunderstood your explanation, BradtheRad. Thanks for clarifying and thank you, FvM, for helping with the clarification.
Zorro, I immensely appreciate the wave plots. I hope it's alright if I use it in my project report to explain the wave.
Humza
This is part of a project I'm working on. I have a relay that connects the motor to a small secondary power source when the PWM is low. However the secondary power source is useless since the motor's back EMF is of a greater magnitude than the secondary source's.
Hello everyone.
I'm operating a DC motor through a PWM signal but I'm facing a problem regarding the back EMF generated by the DC motor.
Ideally, I want the back EMF eliminated.
Currently when I connect an oscilloscope across the motor, I find that the voltage across the motor never reaches...
@FvM:
I believe the zero crossing occurs when the coil is in the center of two magnets - just about to change from one magnetic pole to another. The absolute maximum and minimums occur when the magnets are right in front of the coil rims and the secondary maxima and minima we see are a result...
@BradTheRad:
Your explanation sounds like the best one. The waveform you see is a result of the disc moving at nearly 1200 revolutions per minute. Since each revolution makes the coil go through two pairs of magnetic poles, the frequency of the waveform should be twice i.e. 2400 rpm. Or 40 Hz...
I brought the coil closer to the magnets and got a more sine-like wave; showing the comparison of BEFORE and AFTER in the following images. I cannot bring the coils any nearer otherwise I'm positive a better sine-like wave would've been achieved.
Are harmonics an explanation for this behavior...
Hello everyone.
I'm inducing voltage into a coil using 4 magnets that are arranged circularly with alternating poles. You can see from the diagram that when the magnets are moved, EMF is induced into the coil.
I was expecting to see a sine wave produced in the coil but the waveform shown is...
Hello everybody.
I've been using the analog PWM generator of which the schematic you can find here: **broken link removed**
While I understand the functioning of the circuit, I'm unclear as to how the frequency of the PWM waveform reduces to that mentioned on the page.
For people who'd...
@FvM:
Thanks for the response. The DC supply is being used not only to generate the PWM waveform but also to power up opamps in the circuit. I need a constant 12 V supply to keep those opamps powered up thus I need to regulate the unregulated DC supply. Can it be done?
Hello everyone.
I have an unregulated DC supply which I am using to operate a PWM motor driving circuit. When the load is connected, the supply voltage drops.
I need a regulator circuit that will let me regulate the voltage supply. The regulated voltage I require is 12 V and the maximum...
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