Ultrasonic Cleaner Calibration Issue: Power Drops, Frequency Off After Restart (PE Mag 2021)

When first turned on, it does its initial calibration, and seems to settle at about 36KHz. On second start it is supposed to read the calibration value stored during the first start. That does not seem to go right; the unit keeps reducing power to the lowest setting, and output is very low now, at about 20-some KHz. The included diagnostic mode determined the resonant frequency of the transducer (loaded) at about 38KHz, and should be within the allowable tolerance. Anyone else have any experience?

Bill v

Hi

I travel a lot so I'm only now reading the article with interest. I'm contemplating construction and would be eager to hear more of any issues. Usually any problems are documented within the magazine over the next few months, which should take you up to current issue. If nothing within it may suggest the problem is perhaps local (hardware).

Please update with your progress and if I do construct I'll share too.

Regards

Hello,

Glad to hear from you. First of all, I think this is a very clever design. Having said that, I did run into a couple of software based issues. Most projects presented in PE come from the Ausie based magazine Silicon Chip, and this design was published there one year prior to PE. I searched their magazines, and could not find any discussion on this project.
I found 2 issues, in one case the author did not follow the requirements by the chip manufacturer regarding writing data to the flash memory, and a second calibration failed as a result. The second issue was related to the way the author uses the Timer 2 PR2 register. In the project PR2 has a valid range of numbers, and if for any reason the value falls outside this range, the program fails. I am luckily handy with assembly, so I wrote fixes for these issues. If you decide to build the project I will be happy to share the modified firmware. I wrote to the PE publisher about this, and he replied very quickly, and referred me to Silicon Chip. Unfortunately I have not received a response from them.

Cheers, Bill v

Hi

Sorry for the tardy reply, Christmas and all that.

Thanks for sharing. A lot of PE projects originate from SC and the previous publisher did explain why. Having been an avid reader of EE since the 70's I've seen a lot of change and can understand the need for some. One "plus" is as you note that the project may have appeared earlier in SC meaning any issues are likely to have been corrected by the time it appears in PE. I do think though that you may wait some time for any SC reply.

Glad to hear that you managed to find and resolve the software issue. I am not totally clueless regarding such but admit that most of my code is now written using Flowcode, so if I do build I would certainly appreciate your offer. I'm only now just reading part 2 and I can definitely see building it in my future. I do have an existing cleaner, obtained over thirty years ago and it works fine, but it is a little small, maybe about 4" x 4" x 2" but still can shake stones out of their settings as the power is fixed <s>

When I get the time to build I'll share.

Best regards