0
\$\begingroup\$

I'm currently trying to power a Piezoelectric Transducer with an oscillating signal. I am doing this because I want to experiment with "acoustic levitation." The piezoelectric transducer is a 50W 40kHz device. From my understanding, my input power does not have to match this wattage because it is just a maximum power spec.

To produce this oscillating signal, I am using a 555 timer with a transistor at its output so the current is high enough to power a transformer to step up the voltage; to provide a power sufficient enough to turn the transducer on.

I am doing everything step by step so I can make sure everything is working properly and right now I am stuck at amplifying the current from the output.

This is my circuit right now. Schematic I planned on having the transformer connected to the collector, which is why I put a 1k resistor there as a 'place-mat'

The problem lies in the voltage and current timing diagrams. The collector voltage and current waveforms are going crazy meanwhile the base and emitter mimic the square wave perfectly and I can't understand why.

Does anybody have any idea why? Voltage Levels Current Levels

\$\endgroup\$
13
  • \$\begingroup\$ Why would you want to drive a transformer with a collector (current sink or saturated switch) and an average DC voltage of Vcc/2? What LC self-resonance f and Q do you expect? when the transistor is not conducting current? \$\endgroup\$ Commented Mar 22, 2017 at 20:32
  • \$\begingroup\$ This is my first time creating a circuit like this on my own and I'm just going based off what I remember learning from Electronics I in school where we always used the collector to step up the voltage. It seems that I need to review my notes. My basis of thinking was that the base should be half of the source voltage to bias it properly. No? \$\endgroup\$
    – Rayaarito
    Commented Mar 22, 2017 at 20:45
  • \$\begingroup\$ @Dave It's not an appropriate design for use with driving a transformer. Besides, you've not specified any details yet, either. No idea what you want to actually achieve in terms of power (though I know you think the 555 isn't enough to handle it.) You should write more about your ACTUAL goals in the end, so that you can get some more useful help. You are asking for help for one thing, when you really need help for something else (which may, or may not, look like what you imagine right now -- probably at least somewhat different, though.) You probably want a center-tapped primary, at a guess. \$\endgroup\$
    – jonk
    Commented Mar 22, 2017 at 20:48
  • \$\begingroup\$ The ridiculously high base and emitter currents are an artefact of the base resistor being far too low. \$\endgroup\$
    – user16324
    Commented Mar 22, 2017 at 21:10
  • \$\begingroup\$ @jonk thank you for the reply. I edited my post to provide more detail. The ultimate goal is to get the transducer to vibrate at a high frequency of my choice. I will be adding a POT to 555 so I can adjust the frequency. I just didn't add it to the circuit because its just something I can add on my own when I make sure everything is actually working properly. I'm starting to have the feeling that I need to take the textbook out and actually reexamine how I am going about achieving my goals. Is there any keywords you can advise me to look up to appropriately drive a transformer? \$\endgroup\$
    – Rayaarito
    Commented Mar 22, 2017 at 21:26

1 Answer 1

1
\$\begingroup\$

This is probably a simulation artifact.

What simulator are you using? Are there any configuration parameters such as minimum time step that can be changed? Or selecting a different solver maybe?

\$\endgroup\$
6
  • \$\begingroup\$ Thank you for the fast response. I am using Multisim so I can change the minimum time step. Do you think it is too small so its "grabbing too much noise" causing it to go haywire? I'm sorry but what do you mean by selecting a different solver? \$\endgroup\$
    – Rayaarito
    Commented Mar 22, 2017 at 19:57
  • \$\begingroup\$ Often unexpected results occur if the time-step is too coarse rather than too fine, but a fine time step increases the simulation time. With some other simulation programs they have an option to use different methods to solve the equations in the simulation - they can give different results in some situations. Multisim may not. \$\endgroup\$ Commented Mar 22, 2017 at 20:04
  • 1
    \$\begingroup\$ @Dave The simulator is probably working with an infinite rise time on the 555. That will turn into ringing in the rest of it. If you can adjust the rise time do so. If not, add a small cap from the base to ground of Q1. 1nF or so. It wont hurt the design either. \$\endgroup\$
    – Trevor_G
    Commented Mar 22, 2017 at 20:07
  • \$\begingroup\$ @Dave You will also need a flyback diode across that transformer. \$\endgroup\$
    – Trevor_G
    Commented Mar 22, 2017 at 20:09
  • \$\begingroup\$ @Trevor - you must not have a flyback diode or you will clamp the wanted signal. You may need another winding on the transformer with a diode back to the supply to reset the magnetic flux. \$\endgroup\$ Commented Mar 22, 2017 at 23:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.