Using an inductor to generate a magnetic field?

Thread Starter


Joined Sep 27, 2012
Hey guys,

I'm working of a project for school that revolves around "sending and receiving" magnetic fields to operate a robot.

Basically, I'm trying to transmit a magnetic field at a fixed frequency generated from an inductor to a receiver composed of two inductors, and a bunch of other components to measure/ modulate the amplitude. Inductors I'm using are all 1.16mH. I asked my professor what frequency wave I should try to generate, and he said 15kHz is what worked best for him.

I figured I could just build an H-Bridge with PWM from a microcontroller to drive a series LC tank at resonance, but it doesn't seem to be working. The H-Bridge is outputting the correct square wave, but I'm not seeing a sine wave between the inductor. I know the H-Bridge is working right, because I tested it with a motor, and could make it rotate both ways at a variable speed. Also, it looks like my microcontroller (a variant of the intel 8051) can't PWM greater than 1000hz.

Next, I googled a little bit, and came across this: More specifcally, I tried to build Figure 7 on page 6. The output wave of that circuit was a sine wave, but it was sort of disfigured at both ends.However, what was weird that instead of resonating at 14.8kHz like I hoped for, it did so at 128kHz. Also, changing the capacitor only slightly modified this value, even when replacing a 0.1uF one with a 100uF one. I wish I took a picture of the weird wave but I didn't, sorry.

I then went on to testing a few more fruitless ideas/designs and googling for information for hours, but came up with nothing. And here I am asking for help. Do you folks know how I could build a magnetic transmitter or what I'm doing wrong?

I know this is really wordy, and probably pretty hard to understand, given the nature of the project, so I'm really thankful if you got down this far!