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I'm trying to build a small sized ultrasonic cleaner. I bought a couple ultrasonic transducers (ranging between 40kHz - 102kHZ and 15 - 35 watt) which I want to play around with.

There are already quite some driver boards and transducers out there, but I really want to keep a small form factor. Also I try to make a setup where I can easily play around with different transducers, so be able to change the frequency and supply voltage with little effort

I was thinking about creating a setup with Arduino so I can easily and precisely change the PWM frequency. I found the circuit below as a starting point from Ultrasonic schematic source:

Ultrasonic schematic

I'm trying to control a 35W 40khz transducer which is widely available: transducer link

Now I changed the first 555 timer part of the circuit with the Arduino. Resulting in the following:

Arduino ultrasonic cleaning circuit

But for one reason it's not working properly. It's drawing some current but not very much and seems not to do so much. As a power supply I'm using a simple bench-top power supply (0-30v, 5A)

What am I doing wrong and is there otherwise another way I could drive the Ultrasonic transducer using an Arduino?

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    \$\begingroup\$ This is most likely a wiring or software problem. Also, you don't need the CD4013, the Arduino can output two 180° phase shifted PWM signals by itself. \$\endgroup\$ – Janka Aug 8 '18 at 14:44
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enter image description here

Figure 1. Poor bridge driver circuit.

The problem is that of a badly designed bridge driver. The CD4013 is driven from a 5 V supply so the outputs (1) and (2) can only switch between 0 and +5 V. T1 and T2 are configured as voltage followers so the emitter can only reach 5 V less 0.7 V, the voltage drop across the base-emitter junction. The highest voltage at (3) or (4) is 4.3 V despite being powered from 25 V.

Note that the original circuit is all 12 V so the bridge may be able to switch between about 1 and 11 V.

You'll need to use a proper H-bridge driver circuit.

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  • \$\begingroup\$ Okay, good to know. Do you have a good reference to start with? I was already planning on trying to replace the BD679 and BD680 with NPN and PNP mosfets: IRL520 and IRF9530, would that maybe do the trick? \$\endgroup\$ – Ruben Aug 8 '18 at 15:14
  • \$\begingroup\$ I'm afraid not. I've never built one but have read much about them over the years. The problem you are facing is common on stepper motor drivers and H-bridges are available with TTL (5 V) control inputs so I would start looking there. Make sure that snubbers are built-in. Read up on shoot-through too. A readymade bridge shouldn't have this sort of issue though. \$\endgroup\$ – Transistor Aug 8 '18 at 15:18

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