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What's inside an EC Apparatus brand constant voltage constant current power supply used for Electrophoresis - the separation of particles in a fluid by using an electric field.
You can get these supplies quite cheaply on ebay if you look around.
A quick reverse engineering of the circuit provides some insight into what's happening.
en.wikipedia.org/wiki/Electrop...
en.wikipedia.org/wiki/IGBT
en.wikipedia.org/wiki/Snubber
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Опубликовано:

1 окт 2013

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Комментарии : 85

@ivanv754 11 лет назад

Thank you very much for not mentioning the model or brand in the title. That should keep eBay prices low if the demand keeps relatively low.

@tra757200 11 лет назад

You probably don't want to hear that term while talking to your doctor. I used to work in a clinical reference lab and sat near the electrophoresis bench. I don't recall all the different assays they used but I wouldn't want my doctor ordering any of them on me! Excellent tear down Dave!

@whysguy3 10 лет назад

One of the best teardown vids on this channel! :) I wish Dave would take the time to explain the circuit in all of his tear-downs like he did in this video. Usually he will point to some component or sub-circuit, and say "nothing interesting there", and then my hart sinks. Love the channel! i would love to see more explanations like this.

@HambertHM 11 лет назад

My mother does biochemistry and this is soooo familiar to me, lol. Her power supply is custom made from a friend of her who does electronics, it's even older than me and still running! Recently the platinum electrodes failed and needed a new tray.

@jamieostrowski4447 11 месяцев назад

These work great for reforming high voltage capacitors

@mikeselectricstuff 11 лет назад

I took apart something similar a while ago made by LKB - initially spent ages tracing why it wouldn't work - eventually found a mechanical interlock on the output sockets that didn't quite kick in with standard 4mm plugs. It used a more conventional flyback transformer topology.

@tubical71 10 лет назад

All my DIY linear HV PS got these fluctuation problems without my online USV. Nowadays the mains voltage is rather reduced than setpped up. The days of the old Tube based radios and television sets are gone forever! So we have to deal with it, or spend much more money to get rid of it. For low output current (10-100mA) wind your SM PS tranny some more sec. windings to keep aprox. 100V between input and output. This helps the regulator, as well as a good ground! But causes more heat to dissipate

@Mikkel324 11 лет назад

I suspect the fluctuations on the output are caused by fluctuations in the mains input voltage. I think the output voltage is set purely based on the timing of the IGBT switching in relation to the zero crossing, and not regulated based on any sensing of the actual mains voltage. This means that the output voltage is a fixed fraction of the mains voltage, controlled by the voltage setting, and any fluctuations in the mains voltage will appear on the output.

@KX36 10 лет назад

The load on this is a block of polyacrylamide gel. As long as the voltage is vaguely constant the particles will move at a fixed speed through it depending on their charge. Allow them to move part way through the gel and remove the voltage and you can work out their charge from their position. Noise on the voltage doesn't make much difference and the gel isn't exactly going to breakdown from the spikes.

@mausball 11 лет назад

electro-for-eee-sis ;-) Dad got his PhD in biophysics/biochemistry. Used often for DNA and protein analysis.

@jrevillug 11 лет назад

Interesting stuff - that overshoot was a bit unexpected... One thing: as all this stuff is running from the mains frequency, it'd be worth using the line trigger. Much cleaner waveforms, and less fiddling with the trigger settings...

@otherphoenix1 11 лет назад

The circuit behaviour looks very much like a full wave thyristor rectifier, but using the diode bridge and IGBT instead. I.e. The zero crossing pulse starts a timer (firing angle) in the uC and the IGBT turns on just before the zero crossing of the AC waveform based on the timer. Easy test - the higher the voltage the earlier the IGBT should turn on with respect to the optocoupler pulse. I also found a manual but can't link the address! I put it on the forum.

@chuckvanderbildt 11 лет назад

Great stuff, thanks dave. I've been wanting to take one of these apart, but would have gotten in trouble.

@mausball 11 лет назад

Traces on the breakaway tabs match up with the lower edge of the UI board. They were built and tested together, then snapped apart I think.

@maeanderdev 10 лет назад

i guess there is going to be an IGBT fundamentals friday soon... Dear Dave, I'd appreciate that greetings from Germany, Mäander

@arcadianelectronics 10 лет назад

Hi Dave, great video--I love these teardowns. The issue you see with the knob not working when you spin it quickly is most likely because the micro isn't sampling the encoder fast enough. It probably decides that the position hasn't changed when you move it several "clicks" (usually 4) between samples. I bet the designers decided it was OK because who would ever spin it that fast anyhow :) It's a "feature."

@Sixta16 6 лет назад

Yes, a dumb feature, that pisses off any user.

@Afrotechmods 11 лет назад

Electrophoresis is cool stuff - you can read out DNA sequences with very simple equipment! And Dave is right - you don't need a high degree of precision on the output to do it. If anyone wants to learn more about it sign up for the MITx course 7.00x.

@magnuswootton6181 2 года назад

id rather leave gods mysteries a secret. seems like playing god to me.

@tubical71 10 лет назад

an additional "benefit" would be overshooting and/or very high peaks with spike errors and may some low frequency ringing may occur as well. Adding more low freq-gain to the error correction is not the right way. Stabilisation must be prior to the SMPS input.

@EEVblog 11 лет назад

Simple matter of the Rigol being on the teardown bench, and the Agilent being on my main working bench up on the instrument rack. I have two separate benches were I shoot videos, albeit right next to each other.

@EEVblog 11 лет назад

The overshoot was the collector voltage in constant current mode. In voltage mode it does not overshoot on the output as I showed. I didn't test for current overshoot

@Sinusoidal 11 лет назад

I would have guessed the pronunciation of Electrophoresis would be electro-foe-ree-siss but I could be wrong, would need a phonetic definition. Quite surprised by the very wide low frequency ripple voltage, still a very interesting supply.

@djstevovic 10 лет назад

Very nice desulfator for battery charger :)

@Tehsusenoh 11 лет назад

We used these quite often in our high school bio classes. I was a TA, so I've setup way to many experiments with these things. Honestly, I'd never heard of this brand, as we always got Bio-Rad ones, although I'm sure that has to do with who supplied the district.

@Normie_dog 11 лет назад

Electrophoresis moves DNA/ Protein through a gel matrix, this matrix depending on the concentration can have different pore sizes. So depending on the size of the DNA/Protein you can separate by size/charge..with smaller moving faster vs larger particles. The Voltage pretty much just dictate how fast it takes to run your gel. Higher voltage results in faster movement.

@DarcadeLP 10 лет назад

Please do a video on how to create a variable power supply from a pc power supply

@shinigamidestroyer 11 лет назад

Your definition made me wonder if I heard "eletrophoresis" before as I remember doing a lab in high school about something like that O_o

@andrejkiss 11 лет назад

Got an EC575 from the genetics department, as a gift to my department (physical chemistry).

@SwitchingPower 11 лет назад

We have fixed a lot of BioRad Electrophoresis Power Supply's and they are a pain to fault find and fix. We now have made ourself a BioRad repair kit whit the most common failed parts in it.

@sysmatt 10 лет назад

Great stuff... I love reverse engineering some mystery hunk of junk. Keeps you sharp! and you usually learn something new. Often, now NOT to do something ;-)

@otherphoenix1 11 лет назад

I'm pretty sure it's closed loop feedback control, just a really slow bandwidth, or else Dave would be getting closer to 110Vdc instead of the 100Vdc he commanded. It will still have a hard time rejecting mains fluctuations. The microcontroller must be getting output voltage+current measurements for the display, not much harder to put in a dumb PI (or even just integrator) to regulate the "firing angle"/IGBT drive.

@EEVblog 11 лет назад

For quick hack build videos I'd recommend Hack A Week.

@tubical71 10 лет назад

For the slow voltage changing, it´s a problem all HighVoltage PS got. Due to fluctuation of the mains input in terms of 0.1-2Hz If someone want to get rid of these, the circuit would be -by far- more complex. Rectify the mains. Store it in 1.000müF/400V cap per 10mA of output current. Build up a StepUp SMPS, to overcome the mains input fluctuation. For a true independent output voltage hook up a online USV prior to the PowerSupply, it´s cheaper sometimes.

@pmckinlay653 11 лет назад

Speaking of BioRad, their newer SMPS units are very slick bits of gear. That said, they're far more difficult to fault find and repair!

@OnlyKnowsGod 9 лет назад

How is the base of the igbt regulated from a digital source?..... I could get my head around a variable resistor. But how the heck does a semiconductor chip produce differing voltages to control the base?.

@gregoberfield 11 лет назад

Dave I've noticed that when you need to grab a quick measurement you almost always reach for your Rigol 2000 -- any reason you go that way vs your Agilent?

@EEVblog 11 лет назад

It only stays there for 30sec, and you can turn it off if you really want.

@FrozenHaxor 11 лет назад

Because it went through a bridge rectifier. You multiply that voltage by a root square of two.

@ioanniskyriakidis1495 6 лет назад

Well, after all those years the schematic was not found yet? Anyone please?

@mkuraczyk 11 лет назад

Any plans for HP 35660A DSA Upgrade Investigation Part 2 video? :)

@pmckinlay653 11 лет назад

Not 100% here, but I may have seen that model marked as a BioRad... I get Electrophoresis supplies in for repair relatively often!

@diggithal5054 10 лет назад

Electroph..ff..f..what?!?? :) nice video! Thanx!!

@NickStallman 11 лет назад

I've heard of it but I cannot for the life of me figure out where from. Its obscure enough to recognise it instantly.

@raguaviva 11 лет назад

The 'pho' in electrophoresis sounds like in 'fox' , and the 're' in the 'resis' part sounds as in 'rich'

@-vermin- 11 лет назад

You are not wrong.

@Mydrac 10 лет назад

EEVBLOG is more for EE, not just for hobbyists. Nothing personal. IMHO EEVBLOG is more for the purpose of understand what is happening, why the LED is blinking and not just make the LED blink.

@magnuswootton6181 2 года назад

good for runnin neons???

@ElectronicTonic156 11 лет назад

Do I smell a Fund. Fri. video on snubber circuits?

@KX36 10 лет назад

Well those are all possible problems with any poorly designed feedback loop and not specific to having a capacitor there. A well designed loop can minimise or avoid those problems or a poorly designed loop can have those problems even without that cap. If you can't even work out how to compensate a feedback loop properly, you shouldn't be designing power supplies. The feedback loop in the SMPS must be stable, regardless of what's "prior to its input".

@KX36 10 лет назад

A 90W 250V flyback converter would be small, simple, cheap and probably work perfectly well for electrophoresis.

@hrshovon 6 лет назад

KX36 I am making a power supply for such purpose. Can you share some reading material/schematic?

@EEVblog 11 лет назад

Took me a while, let me tell you, my brain didn't like it one bit...

@AureliusR 11 лет назад

The eevblog logo is blocking the multimeter... why did you start adding that logo in the upper right? Really annoying

@NickStallman 11 лет назад

Or the microprocessor isn't polling it fast enough so it misses transitions.

@commodork 11 лет назад

MikesElectricStuff completely ripped off DaveCad, you have the right to sue. I'd gladly pay through the nose to watch that lawsuit!

@danielhorne6042 10 лет назад

man i want that transformer lol

@thekaiser4333 9 лет назад

+Daniel Hornes I would not pay a couple of thousand dollars for it.

@EEVblog 11 лет назад

Should I have? My wife has, but she's a scientist.

@anonxanon7099 11 лет назад

Dave, you turned it on BEFORE you took it apart! FOR SHAME. ;)

@flyguille 11 лет назад

the pot is dirty, because that it fails when rolling it quickly.

@LZ1SSA 3 года назад

Благодаря

10 лет назад

Don not turn it on! Take it apart! ;-)

@ivanv754 11 лет назад

That is actually a youtube thing. If you hover your mouse over the logo an X button will appear.

@jeromekerngarcia 10 лет назад

the 're' syllable has a "long" e sound, e-lek-tro-fo-ree-sis NOT so very difficult

@mosesusani 7 лет назад

Hello EEV BLOG thanks for the electrophoresis reengineering video please can you do a reverse engineering on DY-300 (china) electrophoresis power supply video Thanks

@lulu137946825 10 лет назад

A colleague and I have created a couple of videos from electrophoresis simulations to illustrate the concept a while ago. You can check them out on his channel (ohickey100).

@KX36 10 лет назад

If you want good DC regulation in an SMPS, stick a capacitor in the local feedback loop of the error amplifier, giving it essentially open loop DC gain. More gain in the error amp means better regulation at that frequency. Most well designed SMPS have this.

@lionlinux 5 лет назад

it's a peace of sheet

@sonicase 11 лет назад

you've never heard of electrophoresis?

@nucleochemist 11 лет назад

Electro-four-e-sis....!

@haz939 11 лет назад

I can't even say electrophoresis correctly!!

@LdHrothgar 11 лет назад

E-lektro-Four-e-sus (my girlfriend has one of these machines... don't ask me why)

@treborrrrr 11 лет назад

Just for future reference re pronunciations. Just go to dictionary[.]com and it'll teach you how to say it by simply clicking the little speaker next to the word :) dictionary. reference. com / browse / electrophoresis

@xzaz2 10 лет назад

@ArunaRubasinghe 11 лет назад

ah, first :D

@Shit_I_Missed. 11 лет назад

it's pronounced ee-lec-tro-for-ee-sis

@SWORDENxxxSPARDA 11 лет назад

I can say it easily cause im greek :)

@danielaustin7643 6 лет назад

the way you pronounced it at the beginning really irritated me, but at the end you started pronouncing it properly. the important thing is the emphasis on the e.