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daudet / seng466-2011-hovercraft

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Add current sensing to lift motors #2

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
We need to measure power in the motors. We can approximate this by measuring 
the voltage drop across the MOSFET with ADC.

1. Use oscilloscope to to see PWM waveform at the motor level and see if it's 
smoothed/rippling or still full PWM (0-Vcc). This will give us approximate 
current waveform and will tell us when to perform ADC (maybe in the middle of 
the duty cycle).

2. Use the Remote Mega or Remote Uno ADC with a resistor in series. The mega 
can amplify 10x or 200x.

3. Might require an op-amp to amplify the voltage.

Original issue reported on code.google.com by degn...@gmail.com on 9 Mar 2011 at 6:49

GoogleCodeExporter commented 9 years ago

Original comment by degn...@gmail.com on 9 Mar 2011 at 6:54

GoogleCodeExporter commented 9 years ago 
I'll start giving this a shot now!

Original comment by Craig.Ir...@gmail.com on 9 Mar 2011 at 7:10

GoogleCodeExporter commented 9 years ago 
deg did most of this work. says it's impossible to do with mosfet, or at least 
troublesome. This is fine if we don't do it. we lose a bit of street cred, and 
now we need to manually instrument power usage. However, this is probably more 
accurate anyway.

Original comment by Craig.Ir...@gmail.com on 25 Mar 2011 at 5:23