KhepeleSibilo
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« Reply #1 on: June 18, 2006, 05:14:56 17:14 » |
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**************** Ultrasonic Cleaner Schematic ****************
Ultrasonic cleaning is a means of removing dirt and surface contamination from
intricate and/or delicate parts using powerful high frequency sound waves in
a liquid (water/detergent/solvent) bath.
An ultrasonic cleaner contains a power oscillator driving a large piezoelectric
transducer under the cleaning tank. Depending on capacity, these can be quite
massive.
A typical circuit is shown below. This is from a Branson Model 41-4000 which
is typical of a small consumer grade unit.
R1 D1
H o------/\/\-------|>|----------+
1, 1/2 W EDA456 |
C1 D2 |
+----||----+----|>|-----+
| .1 uF | EDA456 | 2
| 200 V | +-----+---+ T1 +---+------->>------+
| R2 | _|_ C2 )|| o 4 | | |
+---/\/\---+ --- .8 uF D )|| +----+ | |
| 22K _|_ 200 V )||( + |
| 1 W - 1 o )||( )|| _|_
+-----------------+---------+ ||( O )|| L1 _x_ PT1
| R3 | 7 ||( )|| |
| +---/\/\---+ +-----+ ||( 5 + |
C \| | 10K, 1 W | F )|| +---+ | |
Q1 |--+-+--------------+ 6 o )|| | | |
E /| | D3 R4 +---+ +----+------->>------+
| +--|<|---/\/\--+ _|_
| 47, 1 W | --- Input: 115 VAC, 50/60 Hz
| | | Output: 460 VAC, pulsed 80 KHz
N o------+-------------------+---+
The power transistor (Q1) and its associated components form an self excited
driver for the piezo-transducer (PT1). I do not have specs on Q1 but based on
the circuit, it probably has a Vceo rating of at least 500 V and power rating
of at least 50 W.
Two windings on the transformer (T1, which is wound on a toroidal ferrite
core) provide drive (D) and feedback (F) respectively. L1 along with the
inherent capacitance of PT1 tunes the output circuit for maximum amplitude.
The output of this (and similar units) are bursts of high frequency (10s to
100s of KHz) acoustic waves at a 60 Hz repetition rate. The characteristic
sound these ultrasonic cleaners make during operation is due to the effects
of the bursts occuring at 60 Hz since you cannot actually hear the ultrasonic
frequencies they use.
The frequency of the ultrasound is approximately 80 KHz for this unit with a
maximum amplitude of about 460 VAC RMS (1,300 V p-p) for a 115 VAC input.
WARNING: Do not run the device with an empty tank since it expects to have
a proper load. Do not touch the bottom of the tank and avoid putting your
paws into the cleaning solution while the power is on. I don't know what,
if any, long term effects there may be but it isn't worth taking chances.
The effects definitely feel strange.
Where the device doesn't oscillate (it appears as dead as a door-nail), first
check for obvious failures such as bad connections and cracked, scorched, or
obliterated parts.
To get inside probably requires removing the bottom cover (after pulling the
plug and disposing of the cleaning solution!).
CAUTION: Confirm that all large capacitors are discharged before touching
anything inside!
The semiconductors (Q1, D1, D2, D3) can be tested for shorts with a multimeter
(see the document: "Basic Testing of Semiconductor Devices".
The transformer (T1) or inductor (L1) could have internal short circuits
preventing proper operation and/or blowing other parts due to excessive load
but this isn't kind of failure likely as you might think. However, where all
the other parts test good but the cleaning action appears weak without any
overheating, a L1 could be defective (open or other bad connections) detuning
the output circuit.
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