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L298N + picaxe28x1 (axe020) could work?

hello.

recently i found that the problem with my project is that the motor consumes more than 1 amper (with no load),

because i tried using the L293D it didnt really work well (that's an understatement).

since i would really like to save the trouble of building my own high current H-bridge, i thought the L298N can do the job.

so after measuring i found out that the motor consumes:

1.5 amper with no load.

2-2.5 with the nominal load.

 

i chekced the  L298N datsheet and saw it is designed for max 2 amper nominal current so my questions are:

1. will it be able to work with 2.5 amper or even 3 amper with good heat dissipation (from your experience)? 

2. will it connect to the picaxe28X1 like the L293D did?

i checked the connections of both ICs legs and i am not sure they are identical:

http://www.st.com/stonline/books/pdf/docs/1773.pdf  Page 2 Multiwatt 15 for L298N

http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXyzuxsr.pdf  Page 2 Powerdip (12+2+2) for L293D

 

thanks in advance, shaked.

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Well, I finally got the L298N ( it took sometime to order and ship it)

And now i can see a very strange problem:

As i said im dual channeling the h bridge to one channel that can take more current.

input of 5 volt causes a wanted output in the wanted direction (plus or minus voltage sign) with a droout of about 2 volts, 

I can handle that with a +2v battery, no big deal.

The thing is, when I connect the load (the motor) the voltage drops to 0v, it is like its shot-circuited.

(the motor does work when connected to the battery directly)

I have checked the wiring and it all should work (by reading from the data sheet of the L298N)

Any one has an idea? 

 

I was thinking about cutting the dual channel wires and work with only one channel (half bridge) and check it out

but after all that work I really want to make it work with stronger currents.

Shaked,

What they are showing you is the connection diagram for the pins on the L298 IC.  Enable(pin 6 on IC), In1(Pin 5) and In2(Pin 7) would connect to your uP and Out1(Pin 2) and Out2(Pin 3) would go to the motor. Pin 11 and Pin 6 are connected together.  Pin 10 and Pin 7 are connected together. Pin 12 and Pin 5 are connected together. Pin 2 and Pin 14 are connected together and Pin 3 and Pin 13 are connected together.   Hope this clarifies.

Thank you very much , Now all i have to do is get the L298N and try connecting it this way.

Thanks guys, really dont know how I could have got this information otherwise :)

Chris,

Not at all, my toes are OK.

 

To be honest my friend, I may be speaking out of turn here... I just remember that one particular comment as it [may] pertain to this current issue... HA! (current)...

At anyrate, I am an artie, not a elec. guy or techie and reley on much info from the experts around here so if I stepped on any toes...

Im using only one motor so in my case one 298 will do Im only trying to understand how exactly should i connect the pins in order to make it 4-5 amps in only 2 outpots. 

To be honest, I still dont understand what I see in  page 7 of the datasheet ! 

 If you could explain it, it would be great.

Thanks.

Hi Shaked,

Yes that is the page I am referring to and it is the pin out of the 298 they are showing, not op amps.  Chris, I've hooked them in parallel with decent results.  I did monitor the current sense and use independant PWM control for each 298 though.  You are right, there are better choices out there.

I had a similar issue, but I needed to switch closer to 20 amps and I asked the same question. Here is the answer I got in terms of why parallel is a no-no...

From Robologist:

Simple answer, No. It won't work.

Long answer. The L298 consists of bipolar junction transistors BJTs as the load carrying devices that have a negative temperature coefficient of resistance when going through current overload. One transistor gets hotter as more current is passes, dropping it's resistance which allows more current to pass, getting hotter, etc until failure. Essentially one L298 will attempt to carry as much current as possible, til it melts, then the next, so on, down the line.

Field Effect transistor FET devices like the LMD18200, have a positive temperature coefficient, in which they have a growing resistance as they get hotter. So one FET device will get hot, causing more resistance, which will push current to other parllel FET devices, allowing the first to cool, and allowing a sort of load balancing.

Or you could buy a couple BTS7960B half h-bridges that carry 20+ A  up to 24 volts. (bottom of page, need 2 for full h-bridge) These are surface mount, but not a small package.

 

Here is the post... 

 

well i am referring this http://www.st.com/stonline/books/pdf/docs/1773.pdf in page 7:

correct me if im mistaken, but are these operational amplifiers?

do i really need to use 4 of them? i thought i should just wire the legs to each other..

 

and do you know if there is a need for other connections with the L298N (i read somewhere about diodes of some sort)

or can i connect it refularly just like the L293D ?

Yes, you can connect 2 in parallel.  If you are only using one motor, you can hook up both channels to the motor to increase the current output(Ichannel * 2 = 5A).  If you look on page 7 of the ST L298 datasheet they explain it.