Hi all,
I want to drive a DC motor, and I was thinking that it would be nice to detect the "strain" the motor is in...in other words, how do I detect how much effort/strain a running motor is doing?
Is there a "simple" way of detecting this? I would like to display that value on a LCD...
Thoughts?
~Kam (^8*
The best way to tell the load on a motor is to monitor the current through it. Use a small resistor in the ground lead and filter out the noise with an RC, (say 470R and 1uF) then feed it to the analogue input.
Grumpy, is there a way to shut off a stalled motor without controlling this with Arduino, assuming that stalled motor current > start motor current?
I'll drive a motor remotely with 1-wire and a L298HN.
Maybe it's enough to connect this load sensor to some sort of relay... or maybe they sell rotational switches - I just have to perform a 270° rotation in both ways.
is there a way to shut off a stalled motor without controlling this with Arduino,
Yes you could make a circuit that would automatically shut of the power when a certain current is exceeded. The sort of circuit would be classified as a crowbar over current protection and would be found in a lot of regulated power supply designs.
You could use a rotor shaft encoder to generate pulses while the motor turns and use a missing pulse detector to cut off the power. A missing pulse detector is just a NE555 acting a a one shot monostable with a transistor across the charging capacitor, causing it to discharge every time you get a pulse fro the shaft encoder.
P.S. Did you get the IR detectors I sent?
Thank you for the suggestion Grumpy. They are two different interesting approaches, which one is the easiest to do?
Don't know if I'll be able to mount an encoder, cause I'll use - fasten your seatbelt - an electric screwdriver 
It's the cheapest way to have big torque for small rotations
P.S. Not yet. I let you know when they arrive.
I run some power measurement test with the electric screwdriver.
It's consuming 1.8A @ 3V under load.
Since I'd like to power it from a Cat5 cable used only for 1-Wire bus (thus at least 2 wire couples free), I read an AWG24 cable can reliably carry 0.577A of current... so if I join three couples is it safe?
The stall current is 2.5A but it won't stay in that state for more than 2-3 seconds.
Well 1.731 is not quite 1.8, but let's review what you mean by safe. There are two problems with excess current, one excessive voltage drop at the other end and two heating.
The heating aspect is specified at a temperature that is probably 50C. So it it unlikely to be a problem if you are at say 25C. True it is unlikely to burst into flames but the cable might soften under sustained loads.
Yeah, it's definitely not a sustained load, just short bursts of 6-7 seconds 10 times a day. Plus I could write code to avoid to activate more than one motor at a time.
The only problem is the coexistence between the 1-wire and the power. I plan to use active pull-up but as it's said, "the mileage may vary"
Maybe I could find an industrial AWG22 ethernet cable, so I use only two pairs for power... but I have to find how much is the difference between the standard AWG24 cables...