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!
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.
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.
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.
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
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.
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.
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...
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
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.
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.
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.
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.
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."
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.
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.
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.
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.
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.
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?
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.
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?.
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".
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.
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.
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 ;-)
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
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).
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.
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
These work great for reforming high voltage capacitors
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!
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.
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.
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.
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.
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
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.
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.
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...
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
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.
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.
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.
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.
id rather leave gods mysteries a secret. seems like playing god to me.
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.
i guess there is going to be an IGBT fundamentals friday soon...
Dear Dave, I'd appreciate that
greetings from Germany,
Mäander
Great stuff, thanks dave. I've been wanting to take one of these apart, but would have gotten in trouble.
electro-for-eee-sis ;-)
Dad got his PhD in biophysics/biochemistry. Used often for DNA and protein analysis.
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."
Yes, a dumb feature, that pisses off any user.
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.
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.
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.
It only stays there for 30sec, and you can turn it off if you really want.
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.
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.
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?
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!
A very chunky case, worth $2,000 just by itself! :)
Not 100% here, but I may have seen that model marked as a BioRad... I get Electrophoresis supplies in for repair relatively often!
Got an EC575 from the genetics department, as a gift to my department (physical chemistry).
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.
The eevblog logo is blocking the multimeter... why did you start adding that logo in the upper right? Really annoying
It's a fancy light dimmer! :)
Very nice desulfator for battery charger :)
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?.
Any plans for HP 35660A DSA Upgrade Investigation Part 2 video? :)
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
For quick hack build videos I'd recommend Hack A Week.
Please do a video on how to create a variable power supply from a pc power supply
Because it went through a bridge rectifier. You multiply that voltage by a root square of two.
good for runnin neons???
I've heard of it but I cannot for the life of me figure out where from. Its obscure enough to recognise it instantly.
The 'pho' in electrophoresis sounds like in 'fox' , and the 're' in the 'resis' part sounds as in 'rich'
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".
Well, after all those years the schematic was not found yet? Anyone please?
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.
MikesElectricStuff completely ripped off DaveCad, you have the right to sue. I'd gladly pay through the nose to watch that lawsuit!
A 90W 250V flyback converter would be small, simple, cheap and probably work perfectly well for electrophoresis.
KX36 I am making a power supply for such purpose. Can you share some reading material/schematic?
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.
Or the microprocessor isn't polling it fast enough so it misses transitions.
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 ;-)
Do I smell a Fund. Fri. video on snubber circuits?
You are not wrong.
Electroph..ff..f..what?!?? :) nice video! Thanx!!
Took me a while, let me tell you, my brain didn't like it one bit...
the 're' syllable has a "long" e sound, e-lek-tro-fo-ree-sis NOT so very difficult
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
Should I have? My wife has, but she's a scientist.
That is actually a youtube thing. If you hover your mouse over the logo an X button will appear.
the pot is dirty, because that it fails when rolling it quickly.
Dave, you turned it on BEFORE you took it apart! FOR SHAME. ;)
you've never heard of electrophoresis?
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).
Don not turn it on! Take it apart! ;-)
man i want that transformer lol
+Daniel Hornes I would not pay a couple of thousand dollars for it.
Благодаря
it's a peace of sheet
I can't even say electrophoresis correctly!!
E-lektro-Four-e-sus (my girlfriend has one of these machines... don't ask me why)
Electro-four-e-sis....!
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.
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
I don't think you are pronouncing electrophoresis correctly. Go to Google translate a look it up.
wa
The world's worst regulated power supply..
+Markus Strangl Nah, they use cheap, second rate electrons in the Australian power-grid. That's the problem.
I can say it easily cause im greek :)
ah, first :D
One hell of a shit supply.