Hi ALL,
I would like measure the current of my DC motor on the two direction( 6VDC - 400mA nominal) on the analog input arduino. The goal is to stop the motor when the torque is too high . I don't want to use a R shunt because the consomption is too high and don't use a hall effect sensor because is not appropriate for low current .
I wouldn't worry about the power loss over the shunt resistor at that current level.
If you pick a resistor that's dropping 0.5 volts at 1A for example the resistor is only burning 0.5 watts. P=I*V
You could use much smaller resistance and amplify if that loss is too high.
You would have a small loss of power to the motor from the voltage drop.
The issue is that my system is autonomious. If if add the power lost in the shunt I devide the autonomy time by 2. One more information , it's not necessary that the measurement is accurate , and I want see only that the current go up and a low consomption for long time autonomy
LE_BU:
The issue is that my system is autonomious. If if add the power lost in the shunt I devide the autonomy time by 2. One more information , it's not necessary that the measurement is accurate , and I want see only that the current go up and a low consomption for long time autonomy
Where did you get this divide by 2? Your motor uses 2-3 watts. The current shunt will be in the 0.1 to 0.25 watt range most likely ( depends on the value chosen)
I take you appreciate you can decrease the range of an open core type hall sensor by looping the current wire multiple times through the core. I used a 75A unit to read in the range 0-1A by passing 75 turns through the core. Yes I needed fine enamelled covered wire but it did the job and gave low current resolution.
Alternatively in-circuit hall sensors have extremely low voltage drop and hence wattage loss
OK I will try to loop with a 5amp hall sensor current
And if it doesn't work out you can use that huge coil of wire as a shunt resistor!
10cm of 22 guage will be about 0.005 Ohms for example.
LE_BU:
Hi ALL,I would like measure the current of my DC motor on the two direction( 6VDC - 400mA nominal) on the analog input arduino. The goal is to stop the motor when the torque is too high . I don't want to use a R shunt because the consomption is too high and don't use a hall effect sensor because is not appropriate for low current .
Well you're stuck aren't you? If you exclude the two workable methods to measure current there's not much left...
Remember the wiring to the motor itself forms a current shunt, you can add a sense wires at either end
and use that. Try to avoid using a shunt on the PWM'd side of the motor, very noisy and you
will then need careful attention to symmetrical differential signal routing.