Hello everyone,
This thread is about my experiments with bucking coils based on Chris' Non-Inductive Coil Experiment. I still have a ton to learn and understand, but with time I will get it. I want to say a BIG thanks to Chris and the rest here who put in so much effort in helping others!
Best Regards,
ansen
I am still waiting for some parts to arrive, but here's a list of them:
TRANSFORMER CORE: AMCC-320
Link: https://www.mouser.de/ProductDetail/205-AMCC0320
Later I put clear tape on the core, because apparently they rust easily and definitely flake a lot.
COIL BOBBINS
I designed the bobbins using OnShape, then 3D printed them. (I got the design idea from someone else on this forum, sorry can't remember who.)
If anyone is interested, here's the design: https://cad.onshape.com/documents/70f06e7ec6659a9c674d7924/w/bac78a22749f303d79cfdb22/e/ca907c1e90e33e679e04da66
CURRENT SENSE RESISTORS: 0.01Ω 1% 5W
Link: https://www.mouser.de/ProductDetail/756-OAR5-R010FI
I designed a PCB to mount the resistor and wire terminals, similar to what Chris has. Ordered from China and shipping will take a while.
SWITCHING MODULE: 3D Printer Heated Bed MOSFET Power Module
Since I want to get to work as quickly as possible, I just ordered one of these:
OUTPUT LOAD
I have a couple 12V 500mA light bulbs which should work well for a load.
Hi Ansen,
Looking good My Friend!
Careful design of your coils is worth thinking about, please see the thread: Coil Geometry.
Understanding why this is important is a good first step to Building, as it took me sometime to understand why this is the case.
Cant wait to see more of your progress! Thank You for sharing!
Best Wishes,
Chris
Hi everyone,
So the switching module finally arrived, but the switched output was really dirty, so I decided to do the switching with a TIP120.
But I'm really getting odd results with current measurement. I currently have a symmetrical setup (for testing).
Current sensing resistors are 0.01Ω, probes are set to 1x, scope to 100x. (0.01Ω x1 x100 = 1Ω)
Schematic of setup:
Scope shot (purple is input, green is output:
So for the input it should be showing ~150mA, (it's actually showing 265mA) that's what my power supply is saying and I also confirmed it with a multimeter. The output current value is pretty accurate though.
Also there's a ton of noise in there. Is that maybe because I'm partly using alligator clips?
And here's a pic of my current measurement board:
I'm by far not an electronics expert or circuit designer, so if you have any better ideas or comments I'm ready to listen.
Regards,
ansen
Hello
the problem is the way you have the transistor setup.
the grounding of the sig gen needs to go directly to the emitter and you should have a base resistor that is calculated for the transistor you are using.
You are also running in emitter follower mode which is not a problem as such but it it usually not done as it requires a floating potential above the supply, might be best to ground the emitter and work out a way of sharing a common ground to avoid loops.
If your scope and sig gen are not grounded together then obviously you cant measure the primary current.
your diode is switching off your transistor when the coil is turned on and off and its causing an oscillation.
Try something like this.
Thank you for all that helpful information! The circuit seems to work a lot better and produces a better waveform.
I'm still getting outrageously wrong readings though. I forgot to include it in the previous schematic, but I did use a 2.2k resistor from the sig gen to the transistor base. I also used the same value in this circuit because 500R didn't work.
This is what I have now:
I also have a driver module like this that I will try out:
https://www.amazon.co.uk/HALJIA-IRF520-MOSFET-Arduino-Raspberry/dp/B06XB9B16Z/ref=sr_1_5?crid=LN2YUQPBV3LE&keywords=irf520+mosfet+driver+module+for+arduino&qid=1670090640&sprefix=%2Caps%2C151&sr=8-5
The top circuit you posted is a tip120 is an NPN transistor, the circuit you just posted is for a PNP, that's why its acting up.
Just copy the circuit i sent and replace the led and resistor with the coil, put a diode across your transistor emitter and collector to protect it from kickback.
otherwise you are going to be sending nasty spikes into your signal generator from the looks of it.
Hi Ansen,
In your circuit here:
The problem is the Tip 120 is grounded through all the components.
Move your Tip120 right down to the bottom, where the Gnd is connected directly to the Tip120 Emitter:
Get all your Negatives in the same point, not through components/coils. Low Side Switching.
To be able to switch on the High Side, you need a fully isolated driver.
Best Wishes,
Chris
Hey Ansen
your first config is ok too, you have a common collector config
and you can have common emitter too, check this tuto for helpping you
https://www.electronics-tutorials.ws/transistor/tran_1.html
this is omly for BJT, not the same forMOSFET config
Jagau
your first config is ok too, you have a common collector config
No im afraid its not, the transistor is being switched through the load, you will damage your signal generator.
you need to move the grounding position for this to work.
Hi BMW,
I believe Jagau means with a bit more hardware added to make the Transistor Isolated.
We have an Example here, that I have shared: Reliable and Flexible Switching System
If a Mosfet or Transistor has an Isolated Power Source, both Ve+ and Ve- then the Switch can be High Side or Low Side and this issue wont arise.
You are right, in the Current configuration and yes this is the cause of Ansen's current Switching problems, but there is a way around this issue.
Best Wishes,
Chris
Alright, thanks to your all's wonderful help, the switching circuit is working great. The input/output waveforms look different than in Chris' tutorials, but they are close to 180* out of phase.
For a test, I measured pulsed DC current flowing through a light bulb, and the reading was spot on when I had the scaling on the scope right. Chris did the same here except he used a sine wave:
So I thought, as long as I get the scaling right, it should work with measuring input to the coil. Turns out my scope shows a very unstable reading most of the time or above/below what it should be. Recap on my CSR config: 0.01Ω -> x1 probe -> x100 scope = 1Ω. For the pulsed input I use measure mean (average) and for the output RMS. Anyways, I've got to get accurate measurements if I want to get anywhere. FYI, I got the Siglent SDS1104-E 100MHz 4 channel scope.
Current setup:
Primary turns: 17
Secondary turns: 209
Input: ~3.5V, 60Hz, 25% duty cycle
Schematic:
Scope shots: (purple = primary current | blue = current on sec with load | green = current on shorted sec )
I definitely haven't gotten the right waveform yet. It seems like the secondaries aren't fighting each other. I might have made some silly mistake in the configuration. Anyways, I'll keep working on it.
Hi Ansel
what type of switching do you use for your circuit?
Show me the real circuit you used
Jagau
Looking good, try swapping your output diodes, put your scope across pin 1 and 3 of the transistor, with 3 being connected to ground so we can see what the switching signal looks like to the transistor.
Hi
I tried to turn you on with the little tutorial I provided but I think you haven't read it. So you didn't use the right component to make a switch. Chris tried to tell you but that didn't work too. You used the wrong component to make a fast switch.
We see it very well on your oscilloscope waveform, a darlington transistor like you used is not made to make a switch, it is made to increase the HFE of the BJT in a high way,it is a signalamplifier you have made.
BJT/Mosfet comparison
A Mosfet operates in nanoseconds compared to a BJT in micro second which is very slow and requires current at its base of your BJT
Used a Mosfet you will see a huge difference.
Jagau
Remember you will need a mosfet driver even with the board that you have, A signal generator is unlikely to be able to cope with driving the gate of a mosfet directly at high frequencies but you will be able to do tests, something simple like this might work okay for now.
you can get ready made gate drivers that have all this inside them and just require a power source (like a P3 9v battery) and connections to your mosfet and signal generator.
You're right, Jagau. I was trying to get something going as fast as possible without doing much research. I took a look at the tutorial before and it looked way too technical but after going through it I understood parts of it. I'm starting to realize how much I have to learn yet.
I only have some IRF9520N MOSFETs and maybe 1 or 2 other kinds that I could use right now, but to keep it simple this board which contains an IRF520 should work:
I have two of these, I tested it and it seems to work.
Schematic:
Do you think this module is suitable for this application? Thank you all for your patience with me.
Regards
ansen
Yes that will work to a degree, but to work properly especially at higher frequencies, you need a gate driver.
Use that board with an off the shelf gate driver or the circuit i posted that uses two transistors to amplify the signal from the function generator and you have good results,
There is a nice gate driver board in the resources here: https://www.aboveunity.com/thread/reliable-and-flexible-switching-system/
The IRF520 will tend to get less heated due to its lower RDS on, for what you did used the simple gate driver that BigMotherWale advised you t
this greatly improves the faster discharge of the Mosfet gate, for the protection of the mosfet there are several possibilities such as a real gate driver, but started with this.
Jagau
Hi everyone,
To save myself a lot of trouble in the future, I've decided to build a single channel driver according to the Quadratron plans here: https://www.aboveunity.com/thread/reliable-and-flexible-switching-system/, mentioned by bigmotherwhale. I think it's definitely worth it in the long run.
I'm done with designing the PCB and I hope it turns out well. Are there any design issues that you can see?
Note: the 3D components are just placeholders, and I also changed a couple of part labels.
The schematic:
The board is smaller than an Arduino Uno 😊, it's 68 x 50 mm. I designed it with EasyEDA, which is JLCPCB's design tool. They give you an $8 credit every month if you use their software, so I can order these boards pretty much for free.
Anyways, tell me what you think, I'm open to suggestions.
Best regards,
ansen
Im not a PCB designer so i cant say much but it looks great.
Why didnt you want the whole 4x Quadratron?
It would be good if the quadratron could be updated to SMD, just a preference but its much quicker to work with and there are more driver options.
One thing I will say is make sure your decoupling capacitors across the MC1403 chip supply are close to the chip with low resistance path and of good quality, you may consider increasing the 100n or allowing provisions to do so, it will determine the rise time of the gate pulse. From what I can see it looks ok.
Well, I guess the main reason is that I don't need a 4 channel driver if I'm only going to use 1 channel. Secondly, the part cost quadruples. But maybe I'll make the Quadraton one day.
And yes, it sure would be nice to have an SMD version.
I am almost finished with my driver. Just to make sure, is the IRFP150N MOSFET suitable for doing the switching?
Regards,
ansen
Hi,
100V at 41 A, thats a good one to start with.
Donovan
Update for today: I tested my driver setup, but I'm having a bit of trouble that I haven't figured out. I'm by far not an electronics expert as you have seen by now.
I connected my transformer coil with 3.5V input, but when I applied 12V input to the driver side, the coil side started pulling a lot of power (tested up to 1.4A) even though I wasn't putting in any switching signal. Of course no power should be drawn on the coil side in this exact configuration.
The only thing that I changed in the circuit is that I switched the 1 Ohm resistor with 2.2 Ohms since I couldn't find a 1 Ohm. Maybe you have some suggestions for me...
Regards,
ansen
Hi Ansen,
We need more information, some images, a scope shot of the Gate and drain, we need to see what your Mosfet is doing, it is obvious it is in some sort on On state, thus power is flowing when the Driver is supposed to be off.
I have given you a fully working and tested, High Speed, Driver Here! I have spent many hours testing and improving this Circuit and PCB! The Thread had all the Gerber files and everything.
Your Current Sensing Bridge will not work, you have a short across the Shunt Resistor:
You appear to be shorting components!
Here are the Gerber Files for the Measurement Block PCB, all given freely! Gerber's are all there!
You have all you need and more... Use what I have given you, it all works!
Best Wishes,
Chris
Hi everyone, hope you're doing well.
After getting discouraged because of my driver not working I took a (very) long break and then finally ordered the PCBs designed by Chris. Also ordered more parts and put one driver together. Didn't work, no matter what I tried. (I thought it would be better to figure this out on my own rather than bother you all with it.) Took another long break.
Today I went at it again, started assembling from scratch and testing as I went along. I then took a look at the datasheet for the ILD610 optoisolator, and realized that it doesn't make sense in the way the IC is hooked up according to the internals. Story is this, I couldn't find the IL610 on Mouser, so I bought the ILD610, which I thought was pretty much the same thing. Now that I think of it, I might have been using the wrong IC all along. Can anybody verify that the IL610 and ILD610 are in fact different ICs?
Best regards,
ansen
Hey Ansen,
Yes totally different parts:
ILD610 is an Optocoupler, Phototransistor
IL610 is a Passive-Input Digital Isolators
Make sure your part numbers are exact, and it will work.
Keep up the good work My Friend! It will pay off in the end, please understand, I started from a position where you are right now, many failures led me to useful working tools that will always be useful!
Best Wishes,
Chris
So after ordering and installing the IL610 ICs my driver works perfectly!
What I'm kind of stuck at now is accurate current measurement. I've watched this video from Chris on that topic:
As I mentioned in the beginning, I have 0.01Ω 1% 5W current sensing resistors. I did a quick setup with my power supply and a light bulb to see how accurate my current sensing bridges are. Probes at 1x and scope at 100x (0.01 * 100 = 1).
What I found out is that the current measurement on the scope varied wildly depending on the scope settings. There was only a specific setting/scale that showed a pretty accurate measurement compared to the power supply. I'm wondering if I should get 0.1Ω resistors instead, since 0.01Ω is so little that the noise threshold is causing interference etc. Any thoughts?
Best regards,
ansen
Good Job Ansen! I am pleased you are 100% operational now!
The Resistors are cheap, maybe get a few of both? They will be good for different resolutions.
Best Wishes,
Chris
Chris,
The 0.1Ω open air current sensing resistors that you are using seem to have become scarce, I can hardly find them anywhere. There are some on Alibaba, but I don't want to order a lot. What about different models like this one BPR58CFR10J ?
Or should I switch to SMD? There are resistors like WSHP2818R1000FEA that I think might work.
ansen
No one online at the moment
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