I have a motor that could draw 30+ amps (31ish)
I want to put some safety room in the design
can i use 2 modules in some way to split up the
current to each one?
m
Some modules can be paralleled, but they have to be designed for it. The VNH5019 does not list this as a feature, so I wouldn’t bet on it working.
Instead, I would look at a controller that is rated for the draw in question, such as the bigger RoboClaw or Sabretooth controllers.
Hello.
You can combine two VNH5019 drivers to power one motor. The datasheet recommends accomplishing this by using each of the two motor drivers as a half-bridge. You might consider using our dual VNH5019 motor driver shield as it has two VNH5019 drivers. Instructions on how to use the shield to power a single motor can be found in the “Using the Driver in Single-Channel Mode” section of its user’s guide.
Please note, in this configuration, the dual VNH5019 motor driver shield can deliver a continuous 24 A (60 A peak) to a single motor, but if your motor draws more than 24 A continuously, you should not use it with this board.
- Jeremy
I just connected the motor up to a battery and ammeter, it draws 20 amps NO LOAD on it
Its a blower motor, I think there will be moderate load, but I bet it not draw 30amps
but I want some overhead… + I don’t want to loose any protection (over current) if it got jammed
am I reading this right, do I loose over current protection? or just current monitoring?
im also only going 1 direction… I just want digital control of a blower motor
I also can put and prob would some kind of heat sink on…
A motor with a free current of 20 A is probably going to have a stall current rating that is substantially higher than what the VNH5019 driver can deliver even if two drivers are paralleled. I recommend looking at the motor controllers jwatte suggested instead.
- Jeremy
What is the voltage of that motor?
Also, if you only need on/off, you might consider a relay or contactor with a contact rating of > 30A.
Are you using this motor as an actual blower (so “no load” is with the fins installed, and thus the load will be appx 20A) or will you drive some other load with this? Stall load current is often 5x the no-load or more, but installed fins would count as some actual load.
its a blower… moves air!
oh no, I need SPEED control… one direction speed control via a PWM signal
with current monitoring/over heat protection
I really only need I guess a HALF bridge, not a full H-Bridge
this IC turns off after 20secs, if I knew it would work with a heat sink…
the board limits that a bit, with the capacitor there, unless I get one of those small
tape on heat sinks, but not sure if that will be enough
m
If you only need a single direction, then a high quality logic level N channel MOSFET may be all you need. Drive the gate with your control signal. Hook the source to ground and the drain to the load. For optimum robustness, use a MOSFET driver chip, like the 2301 or whatever, between the control signal and the gate.
As a first approximation, look for an IRLB8721.
hmm… ok
I have a FDP6030BL coming to me, as I was thinking the same thing…
I would have to add current monitoring… but I can just use one of
pololu’s allegro sensor boards
would I need to still use a driver ic? with this MOSFET, I would have 4.5v or so on gate
would that have the source to drain low enough resistance to pass say 22amps
with out getting too hot? (how do it read the graphs in data sheet to know)
do I need any thing to protect the mosfet from the CMF from the motor? (flyback diode?)
also… if I wanted to be sure Vgs is enough, I would add a driver
would FAN3111ESX work… its a simple low side driver
im a little confused why drivers have current ratings, as I would think
the current isn’t flowing though them, but though the mosfet they drive
getting quick lessons on mosfets and such 
thanks guys!
At 4.5V, it has a RDSon of 0.024 ohms.
At 22 Amp, that’s 22220.024 == 11.6 Watts, so you’re going to need significant heat sinking to make that work right. The IRLB8721 RDSon is 0.013 Ohms at 4.5V, so a little over half the heat of the FDP6030BL.
A greased junction is approximately 0.5 degrees per Watt, and junction-to-case for your part is 2.5 C per Watt. Find a heat sink with 8 C per Watt, and your junction will see a temperature rise of (0.5+2.5+8)*11.6 == 93 degrees which should be OK. Try something like this: digikey.com/product-detail/e … ND/3511440
(If you can apply a fan or some other air convection, you can get away with something smaller.)
Also note that, if you’re driving the MOSFET with PWM, the time spent in the transition region causes more heat.
That, in turn, goes into why the driver chips have current ratings. The current rating determines what gate resistor you will use, and thus how fast you can switch the given MOSFET on and off. Current times time equals charge, and the gate charge of the MOSFET is what turns it on. A 200 Ohm resistor at 5V for a 25 mA drive current will switch on/off slower than a 5 Ohm resistor for a 1A drive current
A catch diode across the motor is usually a good thing, although when you have a full bridge, you can’t use a diode across the motor; instead, the body diodes in the MOSFET will work okay-ish. They often have high voltage drop, so a counter-biased diode with lower drop would sometimes help. Anyway, for your case, I’d put in a 1N4001 or similar diode across the motor just to be safe.