Hi all, I'm new to Arduino and the forum so apologies if this is already easily found - I couldn't find the answer.
I do sim racing in Virtual Reality, and am looking to simulate with a couple of fans, wind which increases as I drive faster, and decreases as I slow down. I have found a tutorial, identified all the parts and ordered them all. The one question I have though is on the rev3 Motor Shield, there aren't the seperate terminals +/- that were on earlier versions. I understand I need to use the Vin and Ground on the rev3 for the power supply, does it matter which ones I use as there is a vin and a ground in the blue plastic by the motor terminals, and there is a vin and a ground in the black plastic?
I will be using 1.4amp fans (two of them), which are 12v. I understand when a channel reaches 2 amps it reduces the voltage. Is this a gradual reduction, or can it provide 12v all the way up to that point? Just wanted to check that at 1.4amps I still get 12v.
If you read the documentation at the link you posted, it states that the screw terminals (blue) are where you connect the power for your motors 7-12V. The Vin on the black headers just connects directly to the Vin on the Arduino Uno mounted below it (That's how shields work - all the pins connect where used or not)
It further states that if you are supplying more than 9V for the motors (and you are) then you need to cut the "Vin connect" jumper on the back of the board which seperates the "Vin screw terminals" for the motor from the "Vin for the board" so you will want to do that as well. This means you will have to power your Uno from either the USB or barrel plug
That shield unfortunately uses an L298 dinosaur chip that reduces voltage all the time.
Typical loss at 1A is 2.55volt and 3.7volt at 2A (datasheet),
so your 1.4A fans could get about 9volt on a 12volt supply.
At 2x1.4Amp I expect the chip, which has no heatsink, could get rather hot.
Assuming you don't want to reverse the fans...
You can try to halve that loss by connecting the fan(+) to 12volt and fan(-) to one motor terminal.
It would have been better to use a logic level mosfet instead of an H-bridge.
Than you would get (almost) the full speed from the fan.
Leo..
Thanks Leo, I am new to the world arduino's etc, hence my lack of understanding/knowledge. 9v might be okay as each fan moves 200cfm at around 60dB. The tutorial used two 160cfm fans, and reported it was working well. They might even have had that 160cfm reduce as they likely would have hit the same restriction when it comes to voltage. So if my fan speed was reduced, the reduction in noise would be good, and the amount of air being moved should hopefully still be enough. I'll then consider whether I need any extra power and if so move the fan + to 12 volt.
Any recommendations for cooling the chip? I take it you mean the motor shield's motor driver integrated circuit chip (which has l298P written on it), and not anything on the uno? I could connect up a seperate fan to push air over the board, or get a small heatsink, would a small heatsink help enough?
Its annoying that the actual jumper was removed from this revision, in the guide im following, they just pulled off the jumper. Seems a shame to be taking a knife to a brand new item, I guess its what its designed for.
Out of interest, can you point me in the direction of a suitable logic level mosfet? Thanks