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I am trying to direct a bi-directional dc motor that is about 1.5v (i got it from a micro servo and it is about half the size of a 130 dc motor at 1.5 - 3v) with the smallest power source/battery possible. I'll be controlling it all from a micrcontroller.

I was told that MOSFET transistors would be the best thing for this project as it would draw the least amount of power and current for itself and the motors. Could someone tell me if this is the best solution or if there is a better way to establish an H-bridge at very low power? Any and all references, explanations, and links to tutorials would be much appreciated as I am still unclear if MOSFET is the combination of certain transistors to make the h-bridge or if the transistors themselves are considered MOSFETs...

I was using a L293d but that cost too much power and the batteries needed would have taken up too much space.

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  • \$\begingroup\$ How much current does it draw? Can you run it directly from the IO pins of the microcontroller? \$\endgroup\$ – Bryan Boettcher Dec 17 '15 at 15:33
  • \$\begingroup\$ Why don't you just use the electronics from the micro servo as well? \$\endgroup\$ – Icy Dec 17 '15 at 15:34
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    \$\begingroup\$ Have you measured the motors resistance at rest? Some of those little servos have huge stall currents, so it might be worth making some measurements. What did you mean by "I was using a L293d but that cost too much power"? \$\endgroup\$ – gbulmer Dec 17 '15 at 15:36
  • \$\begingroup\$ @gbulmer - the L293d has volt drops on each section of the H bridge of about 1.5 volts. \$\endgroup\$ – Andy aka Dec 17 '15 at 15:37
  • \$\begingroup\$ What power supply voltage are you using for the H bridge? \$\endgroup\$ – Andy aka Dec 17 '15 at 15:38
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MOSFET transistors do not need a current to stay "ON" so potentially they can be lower power. Although you could build your own H-bridge using 2 NMOS and 2 PMOS transistors, I would not recommend that since there are ICs that will be easier to use and have everything you need included.

I found an example of such an IC, the L9110 of course there are more but this a cheap one I could find easily. You can buy ready-made modules using this IC on ebay.

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  • \$\begingroup\$ ON also makes some like this, e.g. LB1938FA; typically these get dubbed "low power, low saturation" or something like that. \$\endgroup\$ – Fizz Dec 17 '15 at 16:05
  • \$\begingroup\$ And this would be able to drive a dc motor from a micro controller from a battery like the cr20 (it is 3v, 800mah)? \$\endgroup\$ – KellysOnTop23 Dec 17 '15 at 16:06
  • \$\begingroup\$ @respawnedFluff that looks great!! is there going to be a voltage drop after the current goes through one of these IC's because i need to direct 2 dc motors which means ill need 2 of these \$\endgroup\$ – KellysOnTop23 Dec 17 '15 at 16:20
  • \$\begingroup\$ Good conduction performance MOSFETs do however tend to need a substantial gate voltage which can be a challenge here. The L9110 looks to have extremely high internal loss. H-bridge losses are per channel, so if you have two each driving its own motor they do not add. But any sag of your supply battery is common! \$\endgroup\$ – Chris Stratton Dec 17 '15 at 16:30
  • \$\begingroup\$ Hey @chrisStratton , I'm the same dope from this question. That LB1938FA from RespawnedFluff 2 comments above looked promising. It had low voltage (i think it said 2 would get it going) and 800mah which i think some lower batteries can handle. You think i should try that out or should this project just be scrapped cause it seems like bi directional motor control in a small container is asking too much for what im capable of... \$\endgroup\$ – KellysOnTop23 Dec 17 '15 at 16:46

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