AA batteries are usually about 1Ah and upwards (some rechargables these days aroun 3Ah each so they can deal with gear and load inertia for motor start surges of a very short period of 1A or more, USB hubs not so well. Other reasons for surging are trying to go forward or even turn and somebody's foot in the way.simplesi wrote:I haven't fully checked things out yet, but schools usually have some little motors than run off 4AAs so they probably good for 5V operation - If we stick to 5V, then USB Hubs might be good enough as sources?
Utilising I2C or SPI expands I/O immensely.I believe H-bridge is the magic phrase when controlling motors so that signal levels switch motors powered from separate supply.
Anyway - my concern is whether the number/type of io is too much/too little.
The problem is you need a self contained system with enough battery powery to power Pi and motors, that sits on the unit and has motors powerful enough to move it. You end up with the energy store -> vehicle weight -> motor power CIRCLE as one increases the others have to.I want as little as possible i/o as it'll make them as cheap as possible.
But I REALLY DON'T WANT too little if it means too many primary schools/people don't buy it as it won't do what they want
So floor robot - 2 motors (1 each wheel) Line Follower light detector needs 1 input or 1 A/D input??
At worst case you only have three levels to detect - line (black), background (white) and unknown (grey) not on paper)Fairground needs 1 motor, maybe 2 if being really clever, and a lot of outputs for lights
Is 4 digital inputs too much - could we just have 2 - do we 2 A/D? - do we need 4 motors to build a quad-copter? (Are we really going to build a quad-copter in a primary????? )
Not seeing that as a problem Lots of little cheap cars run around with rf/ir control - I sure we can add an RPi on top and still have them moveYou end up with the energy store -> vehicle weight -> motor power CIRCLE as one increases the others have to.
The problem comes when you need two energy stores (batteries or packs) when Pi needs a separate 'battery' to avoid motor surges reseting the Pi. This means the extra weight Pi and battery, is more weight for the motors, which often means more energy to drive the weight, so the battery and motor size is upped increasing the weight so you have to increase the energy......simplesi wrote:Not seeing that as a problem Lots of little cheap cars run around with rf/ir control - I sure we can add an RPi on top and still have them moveYou end up with the energy store -> vehicle weight -> motor power CIRCLE as one increases the others have to.
But your saying for line following, we are going to need 3 A/D sensors - that's what we need to know
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