Fine/Coarse potentiometer arrangement for the SZBK07 DC-DC converter

[@JuozasU]

Thanks for great tips and schematics! I used 330R resistor for CV regulation circuit to avoid current runaway problem and can set voltage as low as 1.3V

[@CuriousScientist]

You're welcome! The additional resistor is a great idea!

[@isidoromaich7226]

Great improvement. Those square blue imported "multiturn" presets are actually a single turn with a gear reduction. Depending on the needed adjustment it is always advisable to change them, for coarse adjustment it are just ok.

[@CuriousScientist]

Thanks! This is interesting, I will disassemble one of these potentiometers and check what's inside them. This gear reduction sounds smart but also a bit like cheating.

[@isidoromaich7226]

​@@CuriousScientist Yeah I felt cheated too. No need to disassemble yours, someone already did it: kzbin.info/www/bejne/eHTanHuafbyEhbM But I had to do it myself too to feel 100% cheated :)

[@CuriousScientist]

Nice! Well, technically, they are not wrong when they state "multiturn". :D But, yes it is definitely a misleading thing. Thanks for the video, this was a really nice one!

[@GregOnSummit]

Awesome ... always wondered the best was to do thid. 👍

[@CuriousScientist]

Thank you!

[@catzplayhouse9612]

Model JK-Z5X buck converter, Mine is A button to press for adjusting cc and voltage. How to replace it to a nonstop pot 😀

[@CuriousScientist]

I have never worked on that converter, so I don't know how it works. By non-stop pot, you mean an encoder, right? Anyway, I saved this device on my list, and maybe later I'll look at it and make a video about it.

[@shayanzafar6930]

Good explanation

[@CuriousScientist]

Thank you!

[@damanbh1]

Nice explanation very informative. I do have the same converter but accidentally I shot the vcc pin with ground and have short circuit. Board is no longer turning on can you please suggest? How do I find a shot or a bad component in the circuit?

[@CuriousScientist]

Just buy a new board, they are cheap.

[@okhascorpio]

Installed those blue multiturn potentiometers (big ones), but the one for current malfunctioned (resistance increased to mega ohm) while running 15 amp load at the output. By the way output current increases to max when that potentiometer resistance is high like that.

[@CuriousScientist]

I used those potentiometers too, even have a video with them but I haven't had any issues so far. They work just fine.

[@SAbdullah03]

very informative vod... I understand the voltage controls, but could you please help me understand the maths behind current controls, or guide me towards video or article where I can understand it better and apply it in my projects...

[@CuriousScientist]

Thanks! Look up the datasheet of the buck controller chip. They have all the information there.

[@magnum164]

Good explanation, however I see the coarse adjustment as bad in this example, it jumped to high in voltage unless you turned it more than a little. I can see damaged components if you were to adjust from 3v to 10v that fast. I guess a different value pot would help make the coarse adjustment in smaller steps. Other than that good example, I was looking for some info to do this exact setup.

[@CuriousScientist]

Thanks! Probably, another value would be better. My main goal was to convey a concept, then the viewers can decide what's the best for them.

[@kevorkatamian]

Hi, thank you for the very informative video. I would like to know how I would find out what value pots I would have to get to sum up to the total ohm value of the one pot I would be replacing? For example, the current pot i want to replace is 5k. What 2 pots should i get for Fine and Coarse control?

[@CuriousScientist]

Hi and you're welcome. The question you're asking is just simple math and you kind of already answered it yourself. Pick two potmeters that make up at least the value of the potentiometer that you replace with them. Also, pick some larger ratio between them so the fine adjustment becomes fine. Let's say you want to replace a 100k potmeter, then pick 90:10 or 80:20. With these, the fine has to be at max to reach the total 100k resistance. You can also pick 100:10 and 100:20, or similar ratios.

[@plazmax]

Hello, i wrote parallel but in series is correct, very informative content thank you.

[@CuriousScientist]

You are welcome! I am glad you liked it!

[@saikrishna9888]

Is the same for the digital potentiometers, Can I also do the same things like coarse and fine adjustments in the manner of the same connection as you did, and does it work? Thanks, I need the range of some µA range, is it possible please tell me. thanks

[@CuriousScientist]

Hi! Yes, the principles are the same. However, I don't recommend you to use digital potentiometers to replace the CC and CV potentiometers unless you manage to pick one that is a high voltage one. Keep in mind that the potentiometer that controls the voltage (CV) gets the full output voltage which can go way above the operating voltage of a regular digital potmeter (5 V). MCP41HVX1 probably would suit the application. However I haven't tried these potentiometers, so I cannot tell it by experience, I just looked up the datasheet.

[@saikrishna9888]

@@CuriousScientist Thanks for the reply Good information regarding it Thanks

[@CuriousScientist]

You're welcome!

[@BeetleJuice1980]

since you are so good at arduino (attiny) and coding why not make a pcb with digital pot and an lcd as an add-on daughterboard to this dcdc converter? just an idea! it would be great and lots of people will like it! dont know if a digital pot can be used as a rheostat...

[@CuriousScientist]

It is a good idea, indeed! And actually, it is on my to-do list. I am even taking a course in power electronics to understand the concepts better. However, instead of digital potentiometer, I am planning to use a DAC. It has a higher resolution and better specifications. I can not promise to do it in the near future, but you will definitely see it showing up in my projects.

[@vaderdudenator1]

On your website, the CC diagram incorporates 4 pots but I only see 2 in the video. Which is correct?

[@CuriousScientist]

Hi! Where exactly do you see those 4 potentiometers?

[@vaderdudenator1]

@@CuriousScientist I got mixed up looking at the lower circuit diagram thinking the 100k and 10k components labeled corse and fine were pots and not simple resistors.

[@CuriousScientist]

I see. No worries!

[@JoshuaSchmidt-t9f]

How do you control it using esp32 dac?

[@CuriousScientist]

Similarly as you would do it with the MP4725 DAC. kzbin.info/www/bejne/d6KYZIuCebCdm68

[@JoshuaSchmidt-t9f]

@@CuriousScientist thanks for the video! But I have a question, so I only need to inject DCV from 0-5 and thats it?

[@CuriousScientist]

Well, with the resistor I picked, 0-5 V is the range that you need to inject, yes.