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Author Topic: L298N and pump issue  (Read 1131 times)
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I watched the tutorial and I managed to make the L298N chip to work with a small vibration motor, but I have difficulty running a pump.
1) I have a 5V supply (which actually measures 5.7V). I attach my pump to it an the pump works.
2) I connect my supply to VCC and +5 on L298N and when I attach a small vibration motor to the outputs the motor works.
3) I replace the small motor with pump and pump does not work, it tries to rotate and produces a constant quite noise.

What am I missing here?

I do know the pump is working, and L298N is wired properly. When I measure the voltage across the pump inputs it is 4.6V, while when a pump is not connected it is what the voltage supply gives 5.7.

Any suggestions?

Thanks.
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Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
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The LM298N is an ancient bipolar H-bridge (obsolete IMO), so it has a high voltage drop except at very low load currents. Use a modern mosfet-based H-bridge instead. If you want a ready-made module, then this one http://www.pololu.com/catalog/product/1212 will probably do the job. If you don't need to reverse the direction of the pump, then you don't need an H-bridge, just a logic-level mosfet and a couple of resistors.
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Well the LM298N was really designed for 48V / 36V / 24V motors, not low voltages...  It's voltage drop of 3.5V worst case (IIRC)
severely limits its use at 5V!

There aren't many good modern MOSFET bridges around that aren't surface mount, otherwise the 298 really would
become obsolete.
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Do you know what voltage the pump is supposed to be ?

The pumps I have are all 12 and 24 volt.

You won't get good performance trying to run any of those from 5 volts.
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Thanks every body for the information. I see what the problem is.

michinyon: it is 6V pump and it works well enough with 5V supply.

I am trying to use it with teensy3 and I got some explanation about how to set it up.
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So do you need to run it in both directions or not?
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So do you need to run it in both directions or not?
No, I do not need to change directions.
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In that case, all you need to drive it is a power mosfet, a couple of resistors and a flyback diode:


* Scan 134.JPG (74.4 KB, 1653x1165 - viewed 42 times.)
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dc42, thanks for the schematic. It is helpful.
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