Just wondering, for a future project, can a seeedstudio L298 motor shield be stacked, and connected in parallel for double the current capacity?
~Travis
Are you sure you want to use those chips for high(er) current.
They have a very high saturation voltage (2.5-3.5volt), so are IMHO not suitable for low voltage/high current applications. I would not design/use this chip for <24volt motors.
Leo..
travis_farmer:
Just wondering, for a future project, can a seeedstudio L298 motor shield be stacked, and connected in parallel for double the current capacity?~Travis
No I think not, you'll get current-hogging by the hotest chip, making it even hotter (this is
also known as secondary breakdown when it happens on different parts of the same chip).
You can mitigate this somewhat by mounting the devices close together on the same heatsink.
In general if your driver isn't powerful enough, get one that is. The L298 isn't anything to
write home about anyway.
Your design of MOSFET H-bridge is not going to work for at least 4 reasons, gate drivers are
5V only, MOSFETs are in source-follower configuration, you cannot avoid shoot-through,
and gate drivers can't source enough current for PWM.
Better to buy one I think.
[ Try looking at the datasheets for HIP4081, FAN7388, IRS2001 gate driver chips for how
a MOSFET H-bridge is done ]
While it is possible to design your own MOSFET H-bridge as a learning exercise, you will explode a few components and possibly frighten yourself in the process. If you just want to make the thing work, get a bigger motor control chip of the appropriate size.
My go-to chip for motors up to 30A, 48V is the VNHP2SP30. I've never been able to kill one, despite doing stupid things that have toasted other motor controllers. It doesn't even need a heatsink.
I think that's the one (one of the pololu Arduino shields) that I use for a can-crushing machine,
but its not a chip, its actually 4 discrete MOSFETs and a control chip in one plastic package, hence
the low on-resistance.
These days any design of H-bridge, half-H-bridge or 3-phase bridge that doesn't use MOSFETs or
IGBTs driven by gate-driver chips is crazy - its the cheapest and most robust way, and you only
need n-channel devices. ( OK, that's a bit strong, sometimes pulse-transformers make sense for
high-side drive. )
travis_farmer:
I found some matched-pair MOSFETS on ebay, will they work for my circuit in the previous post?
they are IRFP240 and IRFP9240. (240 datasheet, 9240 datasheet)the datasheets say a max of 200V, but don't seem to list a minimum, that I understood. also, are they logic level gates? I see the Gate-Source Threshold Voltage is 2 - 4V, is that what I am looking for?
forgive me as I am not really used to using MOSFETs.Thanks in advance for any help.
~Travis
No, definitely not logic level. The threshold voltage is when it just barely starts to turn on. It really has no meaning for us. Look at the first chart in both datasheets. The first line at the bottom of the graph is 4.5V. So it has no useful performance below that and 4.5 is really too low.