You’ve no doubt seen this before on the channel, it’s the trinocular microscope that I have reviewed in Voltlog #282 and I’ve also done a bunch of follow-up videos since then on how to improve the camera system. This comes equipped with an LED ring lamp to illuminate the working surface if you’ve used a setup like this for soldering you’ve no doubt experienced the reflections you get from shiny surface likes the PCB material, especially when you start adding flux into the mix. I’ll overlay some images so you can get a sense of what I’m talking about but basically, since the ring light is shining light right from where the barlow lens is, there are these annoying reflections.
Today I want to show you an alternative lighting system that will help go around that problem. This is a system with individual gooseneck LED lamps. Having this flexible gooseneck tube allows you to position the lamps at an angle that would avoid those nasty reflections.
A common mistake when building kelvin 4 wire test leads is to use standard alligator clips because in a standard clip the top and bottom jaw are electrically connected at the hinge point. This kinda defeats the purpose of having separate sense lines if they are getting shorted at some point with the current carrying trace. For a true kelvin connection you would need a special type of alligator clip, like the ones shown in this video, these have a plastic hinge and the top and bottom jaws are not electrically connected. These can be quite expensive if they are made by a good manufacturer but I got mine from aliexpress for cheap, they do not excel in quality but good enough for the type of instruments I am going to be using them with and with the amount of work volume they are going to see on my bench they will last a while.
A while ago I decided to start this project of re-designing the front panel for this power supply to give it more functionality, make it an awesome power supply cause as it is, it’s a good power supply but I think we can make it an awesome power supply. I made an announcement on the channel a while ago so several people joined the project, this is a team effort and right now it’s time to show you the first hardware prototypes and to discuss the choices we’ve made in terms of hardware.
We usually use an oscilloscope for visualizing a voltage over time but sometimes it’s also useful to visualize the current waveform over time. The right way to do it is to get a current probe which can sense the current and convert that to a voltage that the oscilloscope can display however such devices are pretty expensive, they can be around $1000 even for an entry level one like the Rigol RP1001C which is only rated up to 300KHz bandwidth.
But we can improvise something for a much lower cost and it should allow us to visualize the current waveform on the oscilloscope. You’ve probably seen me use a shunt resistor when testing power supply to take a look at the current waveform. Because as you know passing a current through a resistor will generate a voltage drop.
That voltage drop is directly proportional with the passing current and with a round value resistor we can have an easy to use transformation ratio between voltage and current. All we have to do is o introduce this resistor inline between our power supply and the device under test
For example if I have a 1ohm resistor, we have a 1:1 ration, for each mA passed through that resistor we will have 1mV of voltage drop that our oscilloscope can display. Such a circuit will of course have it’s limitations, for example it won’t work very well when testing low voltage low power devices because our resistor will introduce a burden voltage, which will drop our supply voltage to the device under test. This is also not an isolated measurement so it might not be safe when connected with higher voltage circuits.
But there are still a lot of scenarios where you could use this successfully on the electronics workbench so it might be worth building something like this. I want to make this nicer by building it inside an enclosure with the required bnc connector for connecting to the oscilloscope and 4mm banana plugs for passing the current through. I picked this small aluminium enclosure which would be enough to house the resistor, actually the resistors, because there are several advantages to using multiple resistors in parallel.
Alternative to this simple shunt resistor measuring method include the Joulescopewhich is a fully featured dc energy measurement test instrument with incredibly wide dynamic range that allows you to capture the smallest currents next to a jump to a higher current. I reviewed the Joulescope in Voltlog #211.
I never really had any professional LCR meter in my lab so far, I’ve only done measurements using this transistor tester which also features a rudimentary LCR function but that’s about to change because today we’ll be taking a close look at the Hantek TO11 handheld LCR meter.
There are two models for this LCR meter TO11 and TO22 and as far as I can tell the only advantages the more expensive TO22 model has are the extended test frequency range up to 100KHz and a second option for test voltage at 0.3V.
Next let’s mention the naming confusion, there is something going on with the naming of this instrument and I can’t quite figure it out. On hantek’s website you can find this LCR meter listed as model number 1832C and 1833C while I suspect all newer units are marked TO11 and TO22 respectively. I’ve emailed Hantek and asked them to clarify this and confirm whether or not there are any differences and why the two names and they replied saying the two are basically the same, the TO11 being an ODM version.
Here are some images captured during the teardown, click on the thumbnails to get a high resolution image of the LCR Meter internal PCBs.
In this video I’m going to address the issues I found with the Kunkin KP184 electronic load during the review and teardown of the unit but also some issues people mentioned in the comments. There are 7 things I would like to address in total:
Binding post internal diameter issue.
Grounding issue with blue metal enclosure.
Bad solder joints on thick wires coming to mainboard.
IRFP250M mosfet safe operating area, fake or genuine?
Supposed bug in tripping over-power protection.
Supposed noise in constant current mode loop.
Calibration procedure.
Nothing changes in terms of this being the best electronic load you can buy in this price range, II like it and I highly recommend it if you need to test power supplies or batteries, I think you will be pleased with this unit. If you would like to see the review or the teardown video I will link those on screen right now so you just have to click somewhere in this area. As always thank you for watching and don’t forget you can support this channel on Patreon.
In the previous video I reviewed the KP184 electronic load, I showed you all the features it has, I tested the accuracy of the front panel meter but the video was getting quite long and I skipped the teardown for a future video. Well, this is it, it looks like we have a bunch of screws that have to be removed to slide the folded metal cover off.
As you may remember from the previous video I discovered something related to wiring & safety, the earth wire was connected to the bottom part of the enclosure but it wasn’t connected to this blue cover which is also metallic. Now we can see why, this has a thick coat of paint so we can fix this by either scraping the paint away in the area where this makes contact with the bottom part or we could add a separate earth wire which would probably be a more reliable way to fix this.
The first thing I’m noticing is the silkscreen, this board is version 04 and has a date code of November 2019. And there are a bunch of other nicely placed labels for various signals throughout the board. Soldering looks to be nice and clean with the exception of these thick wires coming from the bottom board, which in this particular joint looks like it hasn’t flowed sufficiently, I will have to fix that later. Wires are nicely secured with adhesive to their end connectors and apart from these thick wires coming from the bottom board everything has connectors which makes it easy to disassemble and service.
Checkout the teardown pictures of the Kunkin KP184 electronic load below
Welcome to a new video, this will be a review of a new test instrument I discovered, you know I like electronic loads and I’ve tested a bunch of hobby grade electronic loads in the past, these were sub $50 items and that budget also meant they had some disadvantages like limited power, limited reliability, limited connectivity, limited functionality and limited accuracy. You were basically trading off a bunch of stuff to be able to get a cheap affordable electronic load.
This is the Kunkin KP184 and I believe this will be a game changer for those who are looking to get something a bit more professional but are still limited by budget and they can’t go for the better instruments starting at 500 USD. The unit is delivered in a large box with nice padding protection and inside you get the instrument, a user manual and a few accessories like some spade connector, an RS232 cable and some wiring.
Let’s talk a bit about the specs of this unit, I have the KP184 model which is like their better equipped model, it works with both 110 and 240VAC, the load voltage can be a DC voltage between 1 and 150V, up to 40A, up to 400W. Measurement accuracy is 0.05% + 5 counts for both current and voltage with 1mV and 1mA of resolution, we’ll be verifying that later. There is RS232 and RS485 connectivity with a modbus protocol which is specified in the user manual and there is a piece of software for the PC, you have to obtain it from the manufacturer which doesn’t respond to emails but I’ve managed to source it and I’m gonna put a link to this in the description below the video and I’ll try to connect it towards the end of this video.
Welcome to a new Voltlog, in this video I’m gonna show you how to parfocal your trinocular microscope, this means getting both the eyepieces and the third camera port in focus at the same time and maintaining them in focus while adjusting through the zoom range of microscope from low to high.
This is extremely useful if for example you are using the microscope through the eyepieces, soldering on some board and at the same time you are using the camera port for recording or live streaming. Once you do this procedure, the camera and the eyepieces will be synced in focus even as you adjust a different zoom level but with some limitations, as I will show in a moment, these are the result of the camera optics which will limit the effective zoom range in focus.
Now if you are using a 0.5x barlow lens like I do and like most people doing electronics will be using, you need to consider the fact that the working distance is about 16.5cm between the barlow lens and the work surface. So keep that in mind, because the adjustment we will do later will be happening around that working distance.
Welcome to a new Voltlog, as you may remember in Voltlog #282 I got a new trinocular microscope and then in Voltlog #292 I got a new camera because the one shipped with the microscope had issues. Banggood till this day did not replace the camera which I believe is defective, they kept asking me to try these various settings in the camera menu to improve the brightness but none worked.
Now to get a good image and have both the camera in focus and the eyepieces you will need some kind of reduction, an optical adapter between the camera and the microscope port. So first I got this SZMCTV 0.3X adapter, after reading some reviews who were claiming this will give the best field of view.
After installing this adapter I noticed the field of view was almost the same as through the eyepiece which is great but I couldn’t get it in perfect focus with the limited adjustment available on the adapter and I was getting this tunnel vision which I couldn’t quite explain but it was obviously not what you want to see.
And so I got this newer wide body 0.5 adapter and installed it on my microscope and the problem was solved I could now get my camera into focus at the same time with the eye pieces but with a loss in the field of view due to the 0.5x adapter. Getting the SZMCTV 0.5X adapter would probably also work, that’s a bit cheaper, but I went with the recommendation of getting the newer type of adapter with better optics.
