Hi,
I am using the mentioned motor shield which can be found from a google search for 'Arduino motor drive shield-L298N'
I am using the shield to control a cheap drill
I am currently running the battery from the drill (14v) into the shield
The + - of the motor goes into the corresponding socket into the shield
It all works fine
I am just worried as the chip on the shield is getting hot and after a few seconds of the motor being run, there is a burning smell coming from the shield and the chip is fairly hot to the touch
I think the motor is asking for too many amps as the shields specification is rated for a max of 3a
I am not returning home for a few day so I cannot test this unfortunatly
I am just wondering if anyone has a similar experience and can offer any advice, or am I going to have to knock up my own h-bridge to handle the stress?
If it is getting too hot then the power dissipation is too much. This might be due to too much current but power is the product of both current and voltage.
So while you might be within the current rating you might be outside the power rating.
Using FETs in your own H bridge is often better as the FETs have a lower voltage drop and hence burn less power.
For a discussion of these matters see:- http://www.thebox.myzen.co.uk/Tutorial/Power.html
Rechargeable drill motors can draws great huge gobs of current. If you plan to use the motor to its full capability, it's almost certain the L298 won't handle it.
Even if you're going to be loading it more lightly, you need a heatsink on the L298. Probably a pretty big one, on the order of the ones used on 486 and early Pentium CPUs. In fact, you might actually want to scrounge one, and use it with the fan.
What I'd do is get a nice wide aluminum strap, and attach it to the L298 with thermal compound to get heat away from the chip. Then I'd mount the finned heatsink to that. If I were building the board from a kit, I'd mount the L298 perpendicular to the board, but I suspect that ship has sailed. Make sure the heatsink gets plenty of airflow if there's no fan.
Yes a heatsink was my original plan
I work in an ICT company we have hundreds of the things
unfortunately yes the chip is laying on the board, I looked at the possibility of bending it up but dismissed that idea straight away, could be risen enough to get something under there, even just air
I am using the drill to power the axis of a plotter I am making so only needs very small usage.
I have just been to Maplin and got a heap of MOSFET to make my own H-bridge
which I will be attaching plenty of heatsinks to
EDIT:
seems I'm missing some fundamental knowledge
I have been playing with my new mosfets but am confused about using them with an external power source and wanted to be cautious to my board and ask before I blow it up
could I possibly get a simple description/ diagram of how I need to wire my arduino with mosfet connected to pin 13, for say an LED to blink on and off with external power
It depends on what sort of mosfets you have. In particular what gate voltage they need (this is not the gate threshold). A logic level FET should turn on with a 5V signal at the gate. Drain to the load, other end of the load to the +ve supply. Source to the ground, -ve of supply to ground. Gate through a 100R resistor (for the ultra cautious) to the arduino pin.
If you do not have logic level FETs then you have to use a transistor to generate a gate signal high enough to turn it on.
Thanks, I will have to google the FET when I have it to hand
it was operating an LED using the arduinos onboard power no problem so I guess it is logic level
I am assuming my error was I was not returning a ground to the arduino then, I did not to want the wires coming out of the battery anywhere near it I would have guessed?
would I want to send a wire from the same FET pin that receives the arduino pin to the arduino ground?
Sorry for the over cautiousness but this is arduino chip # 2
