Component Identification: 5-Pin Transformer - Page 1
Forum section: electronics / beginners

author: evildaemond
author_rank: Newbie
timestamp: March 08, 2017, 03:19:07 am
content: Hey Guys,I have been working on Reverse Engineering a USB Ionic Purifier from an el cheepo aliexpress seller as part of a research project at Uni, and I have done everything up to the 5-pin Transformer, the problem comes that this is my first major dive into reverse engineering, and most of my older projects have been mundane at best.I would love some advice on how I can find the transformer or a suitable replacement, I have included a picture of the PCB top half which contains the imprint "KB140213" which I have searched and found no info on and the 5-Pin transformer, which has no identifying marks on it.Images:http://imgur.com/a/15HFGThanks

author: technogeeky
author_rank: Frequent Contributor
timestamp: March 08, 2017, 05:16:20 am
content: Hello and welcome!I have discussed this question on ##electronics, and I have made some spreadsheets (I would link them, but they would just be more confusing) for this purpose. In my case, I had a bunch ofpower(e.g. big) transformers, and I wanted to know what they could be used for after salvaging. So what is the question we are asking? I think it's:Supposewe have an arbitrary unknown transformer in front of us. What steps do we take to completely characterize it?** At least to the extent that we understand everything except its power handling capability; which is important but a harder topic.I am not certain that this answer is correctorcomplete, but I think it's a good start and I hope others will amend the instructions as they see helpful:Measure and record the resistance between every pin and every other pin.Hint: 0L means the two pins do not form an inductive coil (or are disconnected because of a blown fuse).Hint: Check visually to see if a pin is even connected. Often the pin is only there for mechanical support.Hint: If you get a reading near 1 or 2 Ohms, you'll need a more accurate measurement of this inductive coil later.Hint: If you have three pins which seem to be connected, and have approx. the same resistance, this is probably a center-tapped coil.Acquire a 3-12VACsignal source.This can be a signal generator (a sine wave is 'pure' AC), or anACplugpack (or "wall wart"). Not a switching power supply. AC plug-packs are more rare than DC ones I think, but virtually any DC plugpack will be made up of only four (maybe five) parts. If it has many more parts than this, it is probably as switching supply and not a simple transformer based plugpack. Anyway, the parts are:A transformerA fuseA full bridge rectifier (or 4 diodes)A capacitorIt may or may not be obvious that this can be easily disassembled and turned into an AC plugpack of similar voltage by deleting all parts except the transformer and the fuse. (Or simply bypassing them with new wires). This low-voltage AC source can be used to characterize the exact turns ratio of every coil versus every other coil.Apply a this small AC voltage to some coil.Then, we simply measure and record the voltage of this coil, and every other.Hint: Unlike resistance measurements, you do not need to exhaust all possible pin pairs.Hint: If you are unsure about power handling or the ability of a coil to cope with this power dissipation (e.g. you have a truly tiny transformer with truly tiny wires), simply pick the highest resistance coil to plug into (even if this is not the primary of the transformer).Hint: For a full characterization, you would do a sweep over both voltage and frequency (and even waveform, I guess). We're not going to do that.Use a$20 transistor checker(or similar device) to measure the inductance of each coil.Not only will this give us a direct measure of inductance (though we could have already calculated it from previous measurements, I think (fixme: is this true?); we can also corroborate the resistance measurements from earlier.Make the best physical measurements of the transformer that you can with available tools.Hint: If you have a set of calipers or a micrometer, measure and record the diameter of different type of wire.Hint: If you have a set of scales, measure the weight of the transformer. For heavier ones, this can almost directly tell you the power handling capability of the transformer. For light ones, it may be possible to extrapolate a rough bounds on switching frequency (the smaller the transformer, the higher the frequency must be) (fixme:can this extrapolation be made?).Hint: Note any physicalspacing elements, air gaps, copper (or otherwise) shields, special insulation,special insulated/braided wireconfigurations, etc.I think other people can and should extend and correct this list, but by this point you willalmosthave enough information to completely specify the properties of the transformer Finally, you can use the most basic properties of the transformer

author: Ian.M
author_rank: Super Contributor
timestamp: March 08, 2017, 05:46:06 am
content: A small switching transformer like that probably doesn't have a winding with enough turns to avoid saturating it if you apply any reasonable low voltage at power-line frequencies. Instead you need to use a signal generator feeding a single ended audio amplifier (not bridge tied load) with a 3.9 ohm high power resistor in series with the output to protect the amp, if the transformer has a shorted winding. Crank it up to the highest frequency the amp can handle, or to the switching frequency of whatever it came out of if lower, and monitor the voltage across the 3.9 ohm resistor, looking for distortion on the peaks so you can check it isn't saturating. Due to losses, whenever possible you want to power each winding in turn and measure all the voltages (make sure your meter is accurate at the frequency in question, or use a scope), calculate the turns ratios, and average the results for the same winding pair with different windings driven. If there's any space at all between the winding and the outer limbs of the core, sneak a fine enamelled copper wire through to form an extra winding with at least one but preferably two or three turns, so you can measure the volts per turn and closely estimate the turn counts.For ease of measurement, it may help to add a reversing switch so that you can instantly swap the chosen drive winding and the resistor, so you can simply keep the scope probe on the junction of the resistor and the winding, with its ground clip on the amp oV rail. Stick a 32 ohm resistor across the amp output, and a neon across the drive winding to damp any inductive kick from operating the switch.

author: Assafl
author_rank: Frequent Contributor
timestamp: March 08, 2017, 06:34:16 am
content: Since it is a ionic purifier it is probably a high voltage circuit. While probably low energy (so probably not very dangerous - but that also depends on the source) - it may be bad for your DMM.If it Still works you may want to probe the primary side to figure out what the excitation looks like and use a real high voltage lprobe to probe the output. Is it followed by a voltage doubler or ladder?