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Topic: using L293D h-bridge with current sensing for stepper chopper circuit (Read 4476 times) previous topic - next topic

a_g123

And how many of those 3D printers are using L298 drivers for their stepper motors?

Think about it ... those guys will wish to save every penny in materials cost but they don't use L298 drivers. That must tell you something.

...R
yup you have a point there, if you look at those l298n modules on sale in ebay
https://www.ebay.com/sch/i.html?_nkw=l298n+module&_sacat=0
you can see the rather large heat sink and discrete diodes (they are no included on chip)
that module alone easily cost more than those a4988 and drv8825 modules
https://www.ebay.com/sch/i.html?_nkw=a4988&_sacat=0
https://www.ebay.com/sch/i.html?_nkw=drv8825&_sacat=0

on the other hand given the heat sink it would be more likely the l298n can take a full 2 amps driving a moderately high current stepper, that would obviously make a difference in terms of speed
actually i've not actually worked with a4988 and drv8825 but i think they are fine motor drivers, just that i've actually meddled with some smaller mosfets transistors, i noted that small mosfets do not necessarily offer low resistance and large mosfets are expensive. a smaller mosfet with higher resistance would likely need no less cooling that that l298n with a decently sized heat sink and my guess is h bridges with good mosfets are expensive naturally. even if i choose to do the same - separate the driving h-bridge from its control mcu, the good mosfet h-bridge may well be a pretty costly affair in that design.

a4988 and drv8825 (which i think is better) are pretty nice drivers
but as it goes, i'm happy to play with the l298n and even the l293d for my own experiments with microstepping which means doing current sensing

jremington

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on the other hand given the heat sink it would be more likely the l298n can take a full 2 amps driving a moderately high current stepper
Nope. But you will learn.

a_g123

actually an idea is that a 3d printer controller can be made up of 'co-operating' arduinos

some of the boards notably stm32f103 - blue pill - reaches $2 price point on ebay
(the benefit with this soc is that it is an arm cortex-m3 32bit mcu, it does USB natively on chip and runs at a pretty fast 72mhz)
https://www.ebay.com/sch/i.html?_nkw=stm32f103&_sacat=0
and even more recently stm8s a 8 bit mcu - reaches $1 price point on ebay
https://www.ebay.com/sch/i.html?_nkw=stm8s&_sacat=0

could be programmed - 'arduino style'
http://www.stm32duino.com/

that sort of provides some motivation to meddle with them as stepper controllers as now with things like the blue pill, you could literally parse g-codes from a 3d printing file and control 2 motor for instance. hence, the job of running a 3d printer could be split up between 2-3 blue pills controlling separate motors and devices (e.g. a heated bed, monitor temperatures etc)

but this design would detour from the more common monolithic printer controllers design as it would require a co-ordinating host so that the 2-3 arduinos run the printer in sync

a_g123

i found a mosfet h bridge TB6612FNG
https://www.sparkfun.com/products/9457#documents-tab
https://www.sparkfun.com/datasheets/Robotics/TB6612FNG.pdf
unfortunately it seemed this doesn't have current sense pins as well

Robin2

actually an idea is that a 3d printer controller can be made up of 'co-operating' arduinos


but this design would detour from the more common monolithic printer controllers design as it would require a co-ordinating host so that the 2-3 arduinos run the printer in sync
This is all just making unnecessary work for yourself

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it does USB natively on chip and runs at a pretty fast 72mhz
What is the advantage of 72MHz when the job can be done perfectly with a 16MHz chip?

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

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