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Messages - kamelryttarn

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1
Wow thank you both for excellent information!

Yes the 20MHz limit seem to be a switchable feature and I did find some information about it in on of Hanteks user manuals. One of the reason I think I prefer a USB oscilloscope as opposed to a bench model is the compactness. I can bring it with me practically anywhere and connect it to almost any computer I can install the software on.

Absolute accuracy is not extremely important. I need to get a good visual representation of the wave form so I can decide if a change in component value make things better or worse. The specs of the Hantek models is different depending on where on their site you look which makes it hard to compare the different models.

It is a bit outside my price range but their DSO3204 looks promising. However the series comparison specifies the rise time of the 200MHz model at 1,7ns but on the product page it says 3,8ns.

http://www.hantek.com/en/ProductDetail_2_134.html
http://www.hantek.com/en/productdetail_144.html

I like the possibility to have an external trigger and still have 4 usable channels. The network feature could also possibly useful to me.

Is the input capacitance of 25pF considered high and might that be a limiting factor? I tend to use regular RG58 cables and solder them in at my measuring points and I think that could add a lot of capacitance as well. I know it's not optimal but a good scope AND proper probes cost a ton of money so I am aiming for "good enough" but still want a fairly good scope. My dirt cheap 8 channel Hantek has helped me out a lot and I like it but as I said, 100kHz bandwidth is VERY limiting when dealing with frequencies above mains or audio. The fact that it's DC bias only also presents a challenge a lot of times.

EMC immunity is one thing to consider but the another is ground loops. I use a small "galvanic separator" with a built in DC-DC-converter but it has a connector for 5V-power so I could use battery or an external DC-supply of my choice. The built in works well with my Hantek1008B but perhaps I will not be able to power a higher end USB oscilloscope.

2
First off I would like to ask you to refrain from suggesting non Hantek oscilloscopes.

I am looking for a 4ch USB connected oscilloscope. I bought the Hantek 1008 a couple of years ago and I like but it has very limited bandwidth at only 100kHz. When fiddling around with the royer induction heater I realized I couldn't view the mosfet gate signals with much detail so I need higher bandwidth.

The problem is that I don't really know what bandwidth I need and what the difference between bandwidth and bandwidth limit is. Hantek has a couple of promising candidates but the Hantek6204EU for example has 200MHz bandwidth but 20MHz bandwidth limit. What does this mean?

I would like to be able to see the ringing on the mosfets gate to help me pick the best gate resistor so I guess that if my switching frequency is let's say 40kHz the ringing has an even higher frequency.

Is perhaps 100MHz enough for most of what I need it for or should I go even higher than 200MHz?

3
Capacitor banks / Re: Can crusher attachment
« on: August 29, 2019, 08:03:50 AM »
WoW! Beautiful workmanship! What kind of capacitor bank do you use?

4
The signal is quite good with this setup. Here is a pic of the signal at the optocoupler. As you can see there is no need for more filtration so I am happy with the setup. I was just surprised with the big difference between the two different types and sizes of inductors. I still don't fully understand what they do and how they work so it is very educational for me to try different components and analyze the different results and try to learn from it. Hopefully the results can also help others.

5
Long overdue update to this project. I have been experimenting with a series choke on the ignition pulse and things are looking really good. I also realized that the reason the signal looked so clear at first was that I hit the "roof" of my oscilloscope input voltage. When I hooked everything up with a 20:1 passive attenuator I realized the voltage was actually ~400V which explains my shot optocoupler and constant current driver I was using.

Having realized this I started looking for ways to dampen the ringing and get voltage levels way down. The only thing I had to try at first was a Hammond choke bought for another project. It is specd at 330mH and when I hooked it up with a 680 Ohm resistor to ground I got REALLY nice pulses but the fall time looked a bit too filtered and it is a very bulky choke so I bought a couple of axial ones, one 100mH and one 330uH and tried them out yesterday. They do the trick but I was surprised at how big difference it was between the Hammond one that looks like small transformer and the axial 100mH. The inductance value is about one third but the signal show much more ringing than the big iron core choke. Could this be due to the difference of core material?

The axial one is a Vishay IHD3EB104L

The pic 100mh inductor.gif  shows about 400V but this is due to a software bug and the actual voltage is about 40V

6
Sell / Buy / Trade / eBay tip for induction capacitor
« on: August 26, 2019, 10:58:31 AM »
Just found these. I am extremely interested in buying one myself but I just have too many other projects at the moment

https://www.ebay.com/itm/Induction-Heating-Capacitor/153605789972

7
Electronic circuits / Ultrasonic transducers for cleaning
« on: July 03, 2019, 04:04:53 PM »
I thought it would be interesting to build my own ultrasonic cleaner using transducers available from ebay but does anyone know the best way to mount them to the stainless tank? I know most people glue them but is it possible to attach them with a screw instead? And what is that little screw thingy you can see in some pictures?

https://www.ebay.com/itm/1pc-New-120W-28KHz-Ultrasonic-Piezoelectric-Cleaning-Transducer-Cleaner/232776275029

[edit] found more than I bargained for here: http://www.ultrasonic-resonators.org/design/transducers/transducer_design.html

8
Electronic circuits / Re: Choke-input DC-filter
« on: June 20, 2019, 12:53:58 PM »
But isn't there a risk that the cap placed after the choke will try to feed current back when cranking the starter motor? Short circuit current will be close to 2A . Won't that hurt the choke?

9
Electronic circuits / Choke-input DC-filter
« on: June 20, 2019, 11:43:58 AM »
The other day I received an arduino shield for my motorcycle tachometer project. It will be used to convert the ~12V system to 5V and also provide a little backup power.

Since there is a fair amount of noise on the electrical system I figured it would be a good idea to add some kind of filter on top of the filtration the shield will provide for me so I bought a DC choke of 320mH rated for 600mA with a specified DC resistance of 7.8 Ohm. My goal is to remove some of the worst spikes and dips but do I NEED a capacitor as well and should I place it before or after the choke? I know a capacitor will make the filter circuit perform BETTER but what I would like to know is if I MUST place a capacitor just before or after or if it's just good practice. Can a choke WITHOUT a capacitor even make things worse and possibly break certain components?

My initial plan is to use my oscilloscope and measure before and after the choke to see what kind of difference it makes but if just a single choke can actually make things worse and damage my shield I do not want to do that before I have checked with people who has a better understanding about this than I do. All information I can find about chokes refers to using the after a rectifier bridge @ 50/60Hz

10
Beginners / Re: Why ZVS always use regulated PSUs?
« on: April 09, 2019, 08:45:47 PM »
Hmmmm that is really good to know, thank you both. :D

36 or 48V smps are hard to find here. I was thinking about using my rectified weld transformer to do some tests hahahah. 50V 100A easy. :o Now I just discovered I don't have those big capacitors anymore. But I can find more on junkyard.

Yes I meant the induction heaters with self ressonance. Simple circuit, but very good.

Welders work GREAT as power supplies: https://highvoltageforum.net/index.php?topic=32.0

11
Beginners / Re: Why ZVS always use regulated PSUs?
« on: April 09, 2019, 08:02:09 AM »
I take the old school non-SMPS over SMPS any day of the week. I have destroyed a few ZVS induction heaters (not sure if that is what you menat by ZVS) but I can assure that it was NOT because of a weak power supply. Just as Teravolt wrote I think the reason people use them is that they are so common.

12
Signal peak-to-peak is just over 20V so I need to get it down to TTL logic levels which I planned to do with an optocoupler.

There is a short negative spike that I thought I could just handle with a single diode. But the problem with the rest of the signal is that I can't just make it to square wave with a schmitt trigger because that would still give me something like 3-4 pulses for every falling edge in the ingition system and that would seriously mess up my arduino math (I use hardware interrupts so it will pick up every single hickup on the signal). Hence the idea to use some capacitors and chokes to smoothen out the signal.

13
A while ago I bought a motorcycle and even though there is not need for it, I thought I would make a small arduino-based "computer" for it to monitor different parameters and one thing that would be neat to have is tachometer to see the current rpm. My plan was to use the ignition pulse before the ignition coil. I took my Hantek 1008 oscilloscope and hooked it up and was very pleased with how the signal looked.  It was way cleaner than I had first thought it would be.

Some time later when I had a plan of how to construct it and also an embryo of arduino code for it I connected everything and things did not work as expected so I hooked up my oscilloscope again and this time things looked a lot different. Even though screenshots suggest the time base is the same it was not. The first time I had the software set too 500ms but then I zoomed in and since the actual bandwidth of the 1008 isn't very good I fooled myself a little bit when I looked at the pictures.

I now realize I need the clean up the signal before I send it to my optocoupler and my question is: What is the best way to filter out the noise/ringing without sacrificing too much of the part of the signal I need?

My idea was to basically construct a "speaker crossover" consisting of two capacitors and an inductor in between creating a third order CLC-filter. The two main components to filter out is the ~2kHz ringing when the coil discharges and a much larger in amplitude ringing or possibly "bounce" happening when the coil is charged and that one looks to be close to 17kHz according to my readings.

14
Even if you get 12 or 15 amps at about 40 volts, you have to subtract about 6 amps for idle current , leaving only 6 to 9 amps to do heating of the work.  That isn't very much.  That's only about 240 to about 360 watts.  Something doesn't sound right .
  I would also be concerned about using an autotransformer without an isolation transformer in between.

Is the efficiency and idle current constant? Ie, if you have 6A idle current, is the "wasted" energy constant even when you insert a work piece or is it possible that the efficiency actually increases when there is something in the coil to transfer energy into?

15
Hello everyone!
Another induction heater enthusiast here... I recently purchased the 1800 w unit and was going through all the info everywhere (that spaco.org website was of enormous help, many thanks!)
But anyways... there are several things that I am not so certain about.
First of all, seems like everyone is using switching power supplies (servers or that crazy combo of a dozen laptop power bars=) ... I looked up the price + shipping for the server supply and shipping costs are more than the unit. I started to think, what can I power this with, all the high current supplies are quite expensive.

You could also do like I did and just take an old welder. Voltage and current ratings are often close to what these inductions heaters use.

https://highvoltageforum.net/index.php?topic=32.0

16
Printed Circuit Board / Re: looking for PCB creating software
« on: March 21, 2019, 02:26:09 PM »
I just gave DesignSpark a try following the need to make an arduino proto shield but I can't for the life of me figure out how the program works. I find it close to impossible that I am the first/only one that need to design an arduino shield and that there are no templates I can use???

17
Beginners / Re: Resistor tolerance?
« on: February 14, 2019, 02:27:18 PM »
I made this spread sheet to try and visualize what impact the resistor tolerance has when using them as calibration points

https://docs.google.com/spreadsheets/d/1Cs-OpPVZ9Inlz1PG1GYzi1S5flYNSTyw2RnShtDgI1U/edit?usp=sharing

Rights are only granted for viewing for now

18
Beginners / Resistor tolerance?
« on: February 10, 2019, 05:46:39 PM »
I would like to user fixed resistors as calibration for a couple of Pt100 and Pt1000-to-4-20mA current loop converters and I was wondering if a fixed resistor (metal film or wire wound) with extremely low temperature coefficient changes value or if it can be considered stable?

For example, if I order a 0.1% resistor specified as 100 Ohm, the actual resistance may vary between 99,9 and 100,1 which isn't much but when translated to degrees Celsius it's roughly -0,2 to +0,2.

My question is: Apart from temperature drift, will a fixed resistor shift in resistance value or can I use a low ppm fixed resistor of any value and type and attach a small note to each stating the corresponding temperature once I have been able to accurately determine that?

19
Interesting but what is the crossover freq and filter slope? 200Hz may be reproduced by the woofer. Would be very interesting to see how the electrostatic part of the speaker system performs. Also the measured result is the combination of the speaker AND the power amplifier. What amp did you use to drive the speaker?

20
Vacuum tube Tesla coils / Re: Usable vacuum tube?
« on: November 12, 2018, 12:57:26 PM »
I stripped the transformer bobbin of the secondary windings. Beneath the filament winding there was an unknown winding but since I will only use it for the tube filament I removed that one as well. Can anyone explain why this bobbin has two separate sections for primary and secondary windings when I can usually only find bobbins with a single space for both windings? This one seem much easier to deal with as a hobbyist.

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