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Trying to build arduino based boost converter, The problem is, I have many coils but have no idea what their uh value is, some small ones have numbers on them,

If I use what appears to be a 100uh (by comparing it with 100uh coil images online) and it turns out to be a different value, what will be its impact on the performance or other factors, Can I go with the biggest one I have? Do I need to test their inductance(?) first?

fixed mh to uh

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    \$\begingroup\$ Not sure, but if you are looking to drive indictors with an Arduino's software, you will also need to understand core saturation, as well. But I don't know exactly what you intend, either. So this is just a caution. \$\endgroup\$
    – jonk
    Sep 22, 2020 at 12:55
  • \$\begingroup\$ @jonk good point but i don't know anything about it, mind explaining what could go wrong if I ignore core saturation? \$\endgroup\$
    – asim
    Sep 22, 2020 at 13:39

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If I use what appears to be a 100mh (by comparing it with 100mh coil images online) and it turns out to be a different value, what will be its impact on the performance or other factors

You'll probably find that 100 mH is far too much for most applications but, you never said what application it is so maybe it's secret.

I'd try it on a dummy representative load so that there is no chance you'll overstress something that is important. You will need to test it on load because it is the load that soaks up the energy liberated from the inductor. An open-circuit load means energy liberated continues to grow the capacitor voltage until something turns to smoke.

Try an online calculator to test things out: -

enter image description here

If you enter values for Vin, Vout, inductance, load resistance and operating frequency you can see how the inductor current peaks up and whether you will operate in DCM (light loads) or CCM (heavier loads). Try a few different inductor values to see if 100 mH suits your application.

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  • \$\begingroup\$ Thanks that helps but, what factor decides if inductor value is suitable or not \$\endgroup\$
    – asim
    Sep 22, 2020 at 13:50
  • \$\begingroup\$ If you used the calculator and plugged in values for what you are trying to run at (Vin, Vout, Rload and frequency), you'll see that using an inductor of 100 mH will probably work best if your operating frequency is a few tens of hertz. Because you haven't told me those things I can't be more specific. \$\endgroup\$
    – Andy aka
    Sep 22, 2020 at 13:55
  • \$\begingroup\$ I need to drive dc motor with a resistance of 10ohm, Vin is going to be from 3.7 upto 5v(mostly 5v), Vout will vary from 10v to 20v and sorry I have no idea what frequencies my esp8266 will be capable of, I do have arduino uno and esp32 too but plan to use esp8266 and i don't know what frequency i actually need, 100mh for coil is what i saw in a project online \$\endgroup\$
    – asim
    Sep 22, 2020 at 14:06
  • \$\begingroup\$ Seriously, you should go back to that online project and double check that they didn't mean micro henries (rather than milli henries). 100 μH is suitable for operating at 1 kHz with your sort of requirements. \$\endgroup\$
    – Andy aka
    Sep 22, 2020 at 14:17
  • \$\begingroup\$ Wow, can't believe i wrote mh instead of uh, a stupid mistake on my part \$\endgroup\$
    – asim
    Sep 22, 2020 at 14:22

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