I'm making a simple auto open/close door using Arduino. I want to make it more safety by detecting if the door is jamming or not when motor is running to open/close the door.
If the door is jamming by human hand, dog, cat, things,... => stop the motor immediately
When pull/push the door again => continue open/close following the pull/push direction.
(This safety feature is similar to the CD/DVD drive. When the tray is opening/closing, if we hold the tray, it will stop, pull/push the tray again => will continue to open/close the tray)
I want it to be high sensitivity to avoid injuring the human or animal nearby.
How can I detect the motor jamming using Arduino with high sensitivity ?
you posted in general electronics, so what exactly are you looking for? Motor current sensing? Might not be significant for detection especially if it uses gearbox
This is no easy matter. Maybe You should reconsider the whole idea.
Using beams of light is one technic used. Various mechanical arms sensing obstacles and triggering micro switches. In buses air filled rubber tubes are used but not easy to adjust.
A safer way would be to instruct the users of the gate how to operate it safely.
If it is a brushed DC motor, use a motor driver with current sensing (Pololu sells them).
The motor draws the stall current for a few milliseconds every time it starts moving, but stall current draw for more than that time indicates a stalled motor. In that case shut off the driver.
Some motor drivers, like the "Arduino Motorshield Rev3", have motor current sensing built-in.
Driver grounds have 0.15ohm sense resistors, and the buffered voltages are connected to A0.A1.
Pitty that that board uses lossy unheatsinked dinosaur L298 chips,
so it can only be used for relatively small toy motors.
Leo..
It took me a minute to figure out what @Railroader was saying about the bus doors but I believe I have. Put along the edge of the door, a length of flexible tubing, with one end closed and the other fitted with a low pressure transducer. When it is compressed as it hits an obstruction, you could use the pressure change to trigger a reversal or a stop.
Thank all of you. I think I need to change my mind and my door type. My door is a single swing door. It's not safe design(I think all of you already got finger injured a few times by the swing door).
Also detecting motor jamming by using stall current is not safe at all because my motor has a gearbox inside, with the gearbox, the door can destroy everything before it get stuck. It's dangerous.
Make it safer is not good as change it to safer door design. Using a sliding door is more safety. We can easy detect the obstacles by using the Lazer and IR senser.
Thank you for asking me what is my door type, I did not think about changing the door type before that.
By the way, detecting motor jamming is a interesting topic. I found that many people have asked the same question but the answer is not clear for the beginners like me. Is there any IC/Senser to monitor the motor available on the market?
An ACS712 breakout board could be an easy/safe way to measure motor current.
Put it in the VCC or ground line of the motor driver, and see what A/D values you get.
Leo..
Safety is not an easy task. In Your position the best You can do is teaching those people operating the door how to operate it.
For industrial design it is number one rule to make a safe design. If that's not possible, informing about the danger comes on the list.
A design having loop holes would give a false sence of safety. That's really bad.
Using air traps is a good idea but, speed is still a factor. For instance, at a local industrial dock, an electronic overhead garage door came down on someone's head right above their spinal cord. This caused what is known as a "stinger" and the person was paralyzed for about 30 minutes. The trap worked and the door did stop and go back up but, it still came down too fast. The solution was to 1/2 the speed of the door (it was set 2x too fast!!!)