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Ultrasonic Cleaner Reverse-Engineering (Codyson CD-7810)

My Ultrasonic Cleaner that served me well for a couple of years, suddenly decided to quietly leave this world…

And so I reverse-engineered it’s schematic!

The problem wasn’t in electronic part – it was purely mechanical issue. Because of insufficient amount of adhesive, that was protecting wire solder joints from harmful influence of ultrasonic vibrations and vibration in general, one of the wires just fell off from ultrasonic transducer. I don’t think that this problem is common among these CD7810 Chinese ultrasonic cleaners, because this thing overall has very good build quality – I guess it’s just I was pretty lucky this time :)

And because ultrasonic transducer had metal coating on top of the ceramic plate(which is pretty usual stuff), the wire vibrated off taking away big piece of that metal coating. The ultrasonic cleaner is dead. R.I.P.

But wait! It’s corpse can serve us in a way other than cleaning stuff.. So I’ve decided to reverse engineer this thing. Someone might need this schematic, and it would be a pretty good learning material for beginners.

Here is main board where all the magic is going on(I lifted up some diodes to see their markings, so don’t pay attention to that):

The other board that is not shown here is a Timer Board, which is just seven segment display, some no-name MCU, three buttons and LED. It connects to the main board with three-pin connector(GND, +5V and ON/OFF 5V signal from MCU). And just counts down time switching off the cleaner when the time is up.

When reverse engineering board with through-hole components, it might be very helpful to draw schematic symbols on the back. This approach might considerably speed things up. And after you’ve done, just wipe off those drawings using some alcohol and brush.

Only those two transistor solder joints were really crappy, otherwise it has a good quality soldering joints.

Here is reverse engineered schematic of this ultrasonic cleaner. This model is very popular and manufactured under many brands. But originally it’s CODYSON CD-7810.

Earlier I said that it might be useful for beginners(even if you don’t need an ultrasonic cleaner schematic in particular), and here’s why:

  • You can see how filtering is done, to prevent high-frequency stuff going back to mains.
  • Transformer-less power supply which you can use in some of your projects(but bear in mind, that it’s NOT ISOLATED FROM MAINS)
  • You’ll find nice example of how to drive half-bridge driver through transformer.
  • Self-resonating LC circuit example.
  • How not to make a mess in a schematic drawing? Maybe.. :)

Files:

16 comments

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  1. Steele says:

    Drawing the parts on the reverse side of the pcb is a great tip!
    You might try using a silver infused epoxy to re-apply the wire that came loose from your transducer. I don’t recommend re-soldering because the silver layer on these Chinese transducers are very thin and will burn off easily. A spot of silicone with help keep it from vibrating off again.
    I work for an ultrasonic manufacturer, but our units work at 60kHz and are much more powerful than these Chinese machines.
    I put up a couple of youtube videos featuring ultrasonic cleaners if you search ssteele071. Just weed thru all the other videos i posted to find them.

    1. admin says:

      Hi Steele,

      Thanks for the advice, but unfortunately it’s a bit late for that. I thought I could get away with just soldering the wire back, but as you can guess – I’ve destroyed what’s left of the silver coating. (although I worked with smaller ultrasonic transducers before and I knew that it would probably happen).

      I’ve seen your videos. The test of the new board was pretty impressive. Al-foil piece was turned into nothing much faster than I have seen with any of the Chinese ultrasonic cleaners.

      Regards,
      Phil

  2. Sam says:

    Hi Phil,
    hi all,

    I am new in electronics, and I have a couple of these cleaners. Can you tell me, please, how can I change the oscillator frequency in this circuit ? It is possible to dis-coupling the transducer and use this circuit as a ultrasonic frequency generator at his ends , possibly attaching other loads, as coils or other type of transducers ?

    thank you and Regards.
    ; nice schematic

    sam

    1. admin says:

      Hi Sam,

      I guess, you can change frequency by changing the value of L4 inductor, or by placing additional capacitance in parallel with transducer itself.

      To use it as a generator, you can replace ultrasonic transducer with a capacitor, that has the same capacitance value. (because ultrasonic transducer basically is just a ceramic capacitor capacitor).
      But driving different capacitive or inductive loads with this “generator” will change its frequency. So you might need to tweak the substitute capacitor value a bit.

      P.S. be careful with those circuits, they’re not isolated from mains! and select capacitor voltages at least 1.5x-2x higher than your circuit requires.

      - Phil

      1. David Hoang says:

        Hi admin!
        I am currently repairing circuit board ultrasonic cleaner have the same schematic as website postings diagram.
        But there is a case that I’m quite a headache that killed two transistors Q4, Q5 and resistor R19 although I did learn quite a lot of possible causes.
        Just how much replacement Q4, Q5, R19 is much death, if Q4 Q5 not use BU406, use equivalent replacement.
        I hope admin help me to fix this problem.
        Thank you and Regards!

  3. WALTER LEGO says:

    I was looking at your schematic but could not find the transformer (the biggest in the photo) on it, did you forget to draw it?
    thanks

  4. rajeev mehndirata says:

    Dear

    Can you provide mechanical drawings for the ultrasonic transducer? Of which material it is made of?
    Kindly help me?
    I look forward to your mail.
    Rajeev

  5. Skunk Works says:

    great work….u explained very well with the help of circuit. thanks for sharing and keep posting!!
    Ultrasonic Transducer For Cleaner

  6. nikola says:

    I have the same schematic from above but i have a problem:
    The cleaner it is working but i think it has not the full power so i opened it up and i have what to see. The resistors R20,R21,R13 and R14 are black like they are burned, measuring is showing 21 ohm wich is ok..I also noticed that someone have changed the one Bu406.May this be the problem for burned resistors?
    From what can be this caused?

  7. milo says:

    hey great work, but could you tell the size of the toroidal ferrite core and the no of turns and gauge of the copper wire on the EI 25 1.0 mh.

  8. Essam says:

    Hi all;

    I have an ultrasonic cleaner device & I have a problem on the two power transistors
    and I don’t know from were this damage of transistor.

    could you advice me to check what component ?

  9. chin says:

    Hi, my ultrasonic device malfuction now. (similar to your device)
    I checked and found that no reading at the terminal CN2 (To ultrasonic transducer).
    I mean no AC or DC voltage at CN2.

    Can you please advise me what should I check next?
    The terminal CN2 should have how many volt?

    best regards

  10. janis says:

    Great work!
    My cleaner has the same board and after some years in the shelf it kind of stopped working. The tipical sound goes away after some 10 seconds (it looses generation) and there is only some low frequency buzz (100 Hz). After ca 5 min both transistors get very hot to touch.
    I will use your schematics to check if some capacitors dried.

  11. janis says:

    Was unable to repair thing. It produces correct sound only for some 20 s and then sound dissapears. I looked with oscilloscope probe in vicinity of piezo cable. The circuit oscillates but frequency is way too high: 80 kHz and both transistors get pretty hot. I guess the frequency should be 40 kHz.
    1nF capacitor in parallel to the piezo is OK. The piezo transducer visually seems OK. But could it have internal damage (may be some part of it is lost and capacitance decreased?)

    1. ilde says:

      Hi Janis!

      I had a similar problem as yours. All was due to a loose piezo. I took it apart and cleaned its surface with alcohol, then I epoxied it to the tank again. I Mixed a 60% hardener/40% resin of 5minute epoxy. I let it dry overnight, and it is working ok now.

      Cheers.

  12. rohith says:

    can i have the circuit diagram of CD4820

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