Electronics > Beginners

Using varistor instead of pot. to autom. adjust res. in joule-thief for bat.life

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JS:
How low is low Rds depends on the rest of your circuit, how low you need to go depends on the efficiency you want. If your coil has a resistance of 2Ω having an Rds of 4Ω is too high but there's not much reason to go for single mΩ figures, ~200mΩ seems more reasonable.

JS

Distelzombie:
Ok thank you.

but, again: Is Rds the only thing I have to look for? What about Drive Voltage? Are they even working at this low voltages? Do I have to look for a Vdss that is higher than 30V?
Please answer all questions.

JS:
I don't know if it would work in that circuit as it is, probably not. Of course there are other specs to watch for, you don't need any mosfet with low rds, but the mosfet you pick should have low rds.

JS

Distelzombie:
You're not helping. But on the other I don't know anything and i can't demand you tell me everything.

JS:
  I'd just pointed out some inefficiency spots on the design, you should get it to work and see if efficency is a problem, maybe you are at 60% efficiency and your battery life is enough, so you don't need to mock around any longer, you won't get to 98% with this, efficiency in low voltage is quite low, as a small drop represents a big portion of the total supply.

  To be able to optimize a design you need a lot of things, lot of measurements and knowledge of basic devices are two of them. I can't make measurements and I don't have the time to search for your part, I can suggest where to look for.

JS

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