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Topic: How to make H-bridge for small coreless DC Motor (Read 278 times) previous topic - next topic

Tinker_Tayler

I'm trying to make a remote control helium blimp using an arduino nano.
The plan is for it to have two motors for forward/back, and one for up/down.

As these need to be reversible, I've been looking at making my own H-bridge, but am stuck on component selection. How might I go about selecting the most suitable transistor, and how do I calculate what resistors are needed?

Any help would be greatly appreciated. Did electronics in college far to long ago, and I feel like i knew this... once.

TheMemberFormerlyKnownAsAWOL

Please don't PM technical questions - post them on the forum, then everyone benefits/suffers equally

MarkT

By small coreless motor you mean the ones about 15 to 20mm long?  If so assume a load current upto 2A and
supply voltage of 3.7V (they are all made for single cell LiPo operation I think)

This requires MOSFET H-bridge with very low gate voltages - perhaps a pair of SMT p/n dual MOSFETs?

Note that these motors are highly liable to be biased (the commutator is offset for a preferred
rotation direction for better efficiency at very high speeds).  This means the reverse max speed will be
less than the forward - watch out for that.
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Tinker_Tayler

Yes that's the ones. Ok that's super helpful thank you, I thought MOSFETs were better suited to higher voltage applications, and was looking at BJT transistors as a potentially lighter weight solution.

Did not know that about these motors. Good to know but shouldn't be too much of an issue.

MarkT

Quote
I thought MOSFETs were better suited to higher voltage applications
No, in fact they are ideal for low voltage as they have no fixed voltage loss, being purely resistive.

For really high voltages you use IGBTs, not MOSFETs, as they are more robust.

Anything upto 100V though and MOSFETs dominate.

For a tiny coreless motor you'd use tiny SMT MOSFETs, very lightweight.
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