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Topic: So... which good motor driver for Mabuchi 280 driven pumps? (Read 2878 times) previous topic - next topic

marc426

Hi everyone,

I have to control two small gear pumps (pumping diesel fuel) driven by Mabuchi 280. Their stall torque is given at 3A@6V but I think udner 12V it was below 2A...

Anyway, most of the drivers I've been looking at were L298 based and it seems everyone here dislike these and say they are inefficient and heat very quickly....

Now... what would be a reasonable choice for my application? Why are most driver based around a L298N if they are so bad for the money?


Thanks for the help,

Marc

raschemmel

Unfortunately I cannot speak ftom experience but I can say I have observed many L298 Drivers sold without heatsinks  and I have also noticed that students are notorious cheap (don't want to pay extra for the heatsinked model) and lazy (don't want to look for a  heatsink ) and unwilling to accept ressponsibility when ot overheats.

Robin2

#2
May 26, 2014, 07:04 pm Last Edit: May 26, 2014, 07:06 pm by Robin2 Reason: 1

I have to control two small gear pumps (pumping diesel fuel) driven by Mabuchi 280. Their stall torque is given at 3A@6V but I think udner 12V it was below 2A...

This is the first time I have come across an inverted Ohms law - and a non-linear one.

6 amps at 12v seems a lot more likely. But I don't know if that will let the smoke out.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

raschemmel

#3
May 26, 2014, 07:15 pm Last Edit: May 26, 2014, 07:17 pm by raschemmel Reason: 1
What is the wattage. ?  It can't  be 72 W. More like 18 to 20.

Robin2


What is the wattage. ?  It can't  be 72 W. More like 18 to 20.


Agreed, but the OP was quoting the stall current.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

MarkT

The reason L298 and L293D circuits abound is two-fold:

1)  They are cheap chips.
2)  They are through-hole bread-board friendly components.

They have nothing else going for them really.  The L298 in particular doesn't
have free-wheel diodes even.

The bad news is that for high current there just isn't a good single-chip
controller.

However there are some single-package devices (several MOSFETs in
one package) such as the VNH5019, however they are surface-mount
and expensive.

For 3A you might just be in range of good single-chip MOSFET H-bridges - the LMD18200T
for instance claims 3A (again with a heatsink)

Pololu do a large range of H-bridges its worth looking at...
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Chagrin

Just to confirm, you need to be able to reverse the pumps and you also need to be able to control their speed?

marc426

Hi guys,

I just need to  be able to control their speed... No reverse involved.

I've been actually looking at things like this : http://www.pololu.com/product/2507
A bit pricey for my liking but well...

And otherwise, hobby king makes 10$ 40A ESC (single motor of course...) and, although a bit less compact, it seems like a good option too, what do you think?


Thanks,

Marc

MarkT

For unidirectional control no H-bridge is needed, just a single switching device
(such as a logic-level MOSFET - modern devices have low enough on-resistances
that heatsinking can be avoided if you choose a good enough one).
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

marc426

Hi Mark,

But I guess I would then have to add a frewheel diode and possibly some other conditioning or safety components...
Not out of lazyness but in order to be the cleanest possible, I'd like to have something already packaged.

I will look into TTL-compatible MOSFETs though.
What do I have to look for? A small RDSon? Apart from if it's marketed as such, how can I know a MOSFET is TTL compatible?


Thanks!


Marc

MarkT

Yes, free-wheel diode is always needed for inductive load, but discrete MOSETs are available that won't need
protection, since they will take those stall currents.

The phrase "logic level" or a value of Rds(on) quoted for "Vgs=4.5V" or suchlike.
Note this is not TTL compatible, TTL is not suitable for driving MOSFETs directly as
the high output voltage is well below 5V.  CMOS drives to the rail however.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

marc426

Ok, thanks for the help!

On a related but different topic : I seem to read that I should isolate my DC Motor power from my arduino power supply...

In my application, I'm running everything off a 12V car battery... How could I achieve such an isolation since it's a DC source and I don't have any other source at hand?

Thanks,

Marc

michinyon

You don't need an isolated supply.  What you do need,  is the ability to provide the 3 amps that your motor/pump requires,   by some means other than attempting to get that current through the digital output pin of the arduino chip.   Getting your current from a car battery should work just fine.

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