Help with pulling down a door handle using a motor

I apologize in advance, there’s a lot to read here because I wanted to be detailed. I have set up my Arduino Uno using a L293D Motor Drive Shield and two 9v power supplies (one for the arduino and one for the shield/motor) to take in commands from a connected bluetooth module triggering the door mounted motor to spin and then reverse, with a string tied to both the handle and motor, attempting to unlock a door handle by pulling the handle down and then “re-lock” it by reversing. The way I currently have things set up is with a 100 RPM DC 12V 90N.CM torque Gear Box Motor. This motor obviously does not have enough torque to pull the handle down. Maybe a higher torque motor? I was wondering if anyone could guide me as to what I can do. Thank you!

Note

  • I can’t modify the door or door hinge in anyway as its for a college dorm door.
  • I’m mounting the motor to the door using either removable high strength command strips or a high strength suction cup.
  • The door locks with a push button, and the handle is a regular handle (NOT twist handle).
  • The door will be always locked (pulling the handle down from inside temporarily unlocks it).
  • The door handle requires a decent amount of force to pull down ( a soda bottle filled with roughly 2.7 pounds of water tied to a string pulled it down)
  • I have searched for a while reading seemingly endless similar attempts with no luck.

l1ttledand: I apologize in advance, there's a lot to read here because I wanted to be detailed. I have set up my Arduino Uno using a L293D Motor Drive Shield and two 9v power supplies (one for the arduino and one for the shield/motor) to take in commands from a connected bluetooth module triggering the door mounted motor to spin and then reverse, with a string tied to both the handle and motor, attempting to unlock a door handle by pulling the handle down and then "re-lock" it by reversing. The way I currently have things set up is with a 100 RPM DC 12V 90N.CM torque Gear Box Motor. This motor obviously does not have enough torque to pull the handle down. Maybe a higher torque motor? I was wondering if anyone could guide me as to what I can do. Thank you!

Note - I can't modify the door or door hinge in anyway as its for a college dorm door. - I'm mounting the motor to the door using either removable high strength command strips or a high strength suction cup. - The door locks with a push button, and the handle is a regular handle (NOT twist handle). - The door will be always locked (pulling the handle down from inside temporarily unlocks it). - The door handle requires a decent amount of force to pull down ( a soda bottle filled with roughly 2.7 pounds of water tied to a string pulled it down) - I have searched for a while reading seemingly endless similar attempts with no luck.

OK i will go first.

You are best off doing this with a stepper motor and appropriate controller.

For an all in one solution i would look for EasyDriver - Sparkfun (and lots of EBAY sellers) sell this. Very easy to drive from your processor.

Couple this with an appropriate motor - i personally would use a NEMA 17 stepper (again check on EBAY) as a bipolar stepper - this should give you more than enough torque for the job - however if it does not then use a single pulley mounted on the door to double the torque the motor provides.

Once you have this in hand have a search on Google for Arduino EasyStepper tutorial

Craig

craigcurtin:

l1ttledand: I apologize in advance, there's a lot to read here because I wanted to be detailed. I have set up my Arduino Uno using a L293D Motor Drive Shield and two 9v power supplies (one for the arduino and one for the shield/motor) to take in commands from a connected bluetooth module triggering the door mounted motor to spin and then reverse, with a string tied to both the handle and motor, attempting to unlock a door handle by pulling the handle down and then "re-lock" it by reversing. The way I currently have things set up is with a 100 RPM DC 12V 90N.CM torque Gear Box Motor. This motor obviously does not have enough torque to pull the handle down. Maybe a higher torque motor? I was wondering if anyone could guide me as to what I can do. Thank you!

Note - I can't modify the door or door hinge in anyway as its for a college dorm door. - I'm mounting the motor to the door using either removable high strength command strips or a high strength suction cup. - The door locks with a push button, and the handle is a regular handle (NOT twist handle). - The door will be always locked (pulling the handle down from inside temporarily unlocks it). - The door handle requires a decent amount of force to pull down ( a soda bottle filled with roughly 2.7 pounds of water tied to a string pulled it down) - I have searched for a while reading seemingly endless similar attempts with no luck.

OK i will go first.

You are best off doing this with a stepper motor and appropriate controller.

For an all in one solution i would look for EasyDriver - Sparkfun (and lots of EBAY sellers) sell this. Very easy to drive from your processor.

Couple this with an appropriate motor - i personally would use a NEMA 17 stepper (again check on EBAY) as a bipolar stepper - this should give you more than enough torque for the job - however if it does not then use a single pulley mounted on the door to double the torque the motor provides.

Once you have this in hand have a search on Google for Arduino EasyStepper tutorial

Craig

Here is your google link for the tutorial

http://www.schmalzhaus.com/EasyDriver/Examples/EasyDriverExamples.html

Craig

OK i will go first.

You are best off doing this with a stepper motor and appropriate controller.

For an all in one solution i would look for EasyDriver - Sparkfun (and lots of EBAY sellers) sell this. Very easy to drive from your processor.

Couple this with an appropriate motor - i personally would use a NEMA 17 stepper (again check on EBAY) as a bipolar stepper - this should give you more than enough torque for the job - however if it does not then use a single pulley mounted on the door to double the torque the motor provides.

Once you have this in hand have a search on Google for Arduino EasyStepper tutorial

Craig

Here is your google link for the tutorial

http://www.schmalzhaus.com/EasyDriver/Examples/EasyDriverExamples.html

Craig

Thank you so much for the quick response! It's late here now but I will look into all this first thing tomorrow and get back to you.

Edit: I couldn't help but looking into it now lol. This seems to be exactly what I was looking for. Just a quick question, I see in the tutorial link that it says 12v to power the easy driver. Would the arduino itself also require its own separate power? Also, I found the one you said here https://www.inventables.com/technologies/stepper-motor-nema-17 and the listed Holding Torque is 62 oz-in, just confirming that this will be enough power before I order it! Thanks again!

l1ttledand: Thank you so much for the quick response! It's late here now but I will look into all this first thing tomorrow and get back to you.

Edit: I couldn't help but looking into it now lol. This seems to be exactly what I was looking for. Just a quick question, I see in the tutorial link that it says 12v to power the easy driver. Would the arduino itself also require its own separate power? Also, I found the one you said here https://www.inventables.com/technologies/stepper-motor-nema-17 and the listed Holding Torque is 62 oz-in, just confirming that this will be enough power before I order it! Thanks again!

No idea as there are a lot of variables - i can tell you those motors are very powerful ! Again though - if it not powerful enough - mount a pulley on the door - the same way as you were going to do with the motor and that will double the power of the motor (i think you will find this unnecessary)

Craig

I don't see this as a problem that calls for a stepper motor - I think you just need a straight forward small cheap DC motor.

If you fit a long enough lever to the handle then you ought to be able to reduce the required force as far as you like - at the expense of needing more time to operate. Depending how big an angle you need it to move through, you might need to attach a quadrant to the handle so that the pull cord has a constant leverage. I would have thought it ought to be possible to start with a small DC motor and integral gearbox and a small diameter pulley, and I'd envisage a solution similar to my electronic curtain puller, with a tiny 12V motor driven off a wallwart and using a cheap Arduino clone with an integral H-bridge driver - far less expensive than an official Arduino and motor shield. I would look to attach the motor+gearbox+pulley assembly to some solid object at floor level rather than try to get a reliable mount using suction cups etc.

PeterH: I don't see this as a problem that calls for a stepper motor - I think you just need a straight forward small cheap DC motor.

If you fit a long enough lever to the handle then you ought to be able to reduce the required force as far as you like - at the expense of needing more time to operate. Depending how big an angle you need it to move through, you might need to attach a quadrant to the handle so that the pull cord has a constant leverage. I would have thought it ought to be possible to start with a small DC motor and integral gearbox and a small diameter pulley, and I'd envisage a solution similar to my electronic curtain puller, with a tiny 12V motor driven off a wallwart and using a cheap Arduino clone with an integral H-bridge driver - far less expensive than an official Arduino and motor shield. I would look to attach the motor+gearbox+pulley assembly to some solid object at floor level rather than try to get a reliable mount using suction cups etc.

Can you link to your curtain puller as i am interested in doing something similar ?

regards

Craig

What diameter spool are you using at the motor to wind the string on, a smaller spool if you are not already using the smallest you can, will increase the available torque.

Tom

craigcurtin: Can you link to your curtain puller as i am interested in doing something similar ?

regards

Craig

It consists of a Pololu Baby Orangutan from HobbyTronics, a small DC motor and epicyclic gearbox combination similar to these, an nRFL24L01+ transceiver for wireless logging, a 12V wall wart to power everything, plus an LDR and a few bits of wire and so on. The gearbox output shaft drives a pulley which has the pull cord wrapped around it a few times. The whole thing is tiny - the biggest component is the motor+gearbox assembly which is only about 20mm diameter and 50mm long. I haven't measured the output torque but the stall torque is several times higher than needed to operate the curtains and the motor is only lightly loaded.

Alright an update to my situation, I bought the easy driver and nema 17 stepper motor and now I’m just having more problems… The motor was working fine for a very brief amount of time before it slowed down to a point where now its not moving at all but powered shown by the led on the easydriver and a light pulse when touched from the stepper motor, this all being powered with a 12v adapter, all connections as properly placed as i can tell, and i tried delicately fixing the wiring for several hours too. I’m clearly new to all this but I’m regretting spending the money for these results. I read the replys and thank you for the help, but I’m still hoping to accomplish this, however my budget it now slim to none. In hope of accomplishing this project I now own an arduino uno (obviously), arduino motor shield, dc motor 100 rpm, bluetooth module, stepper motor nema 17 (not sure if working at this point), and sparkfun easy driver (also not sure if damaged or not at this point).

As for adding a lever to extend the handle, I was hoping to avoid this as it looks untidy and sort of makes regular use of the door handle a bit ‘awkward’ in my personal opinion. However, I am pretty frustrated at this point and i’m looking for any other (well documented) solution with the materials I own if possible. I’m all for any advise I can get though! I can really use it.

Edit: In reply to Tom, I used the smallest I could, the door handle just requires too much force for the motor to handle.

l1ttledand: Alright an update to my situation, I bought the easy driver and nema 17 stepper motor and now I'm just having more problems.. The motor was working fine for a very brief amount of time before it slowed down to a point where now its not moving at all but powered shown by the led on the easydriver and a light pulse when touched from the stepper motor, this all being powered with a 12v adapter, all connections as properly placed as i can tell, and i tried delicately fixing the wiring for several hours too. I'm clearly new to all this but I'm regretting spending the money for these results. I read the replys and thank you for the help, but I'm still hoping to accomplish this, however my budget it now slim to none. In hope of accomplishing this project I now own an arduino uno (obviously), arduino motor shield, dc motor 100 rpm, bluetooth module, stepper motor nema 17 (not sure if working at this point), and sparkfun easy driver (also not sure if damaged or not at this point).

As for adding a lever to extend the handle, I was hoping to avoid this as it looks untidy and sort of makes regular use of the door handle a bit 'awkward' in my personal opinion. However, I am pretty frustrated at this point and i'm looking for any other (well documented) solution with the materials I own if possible. I'm all for any advise I can get though! I can really use it.

Edit: In reply to Tom, I used the smallest I could, the door handle just requires too much force for the motor to handle.

OK so post your code first thing - then a picture of your setup might be useful

Have you read the tutorials on the easydriver - in particular the point about adjusting the pot on board to control the amount of current for your motor ? and then measure that at the t1 point on the board

Disconnect the motor from the door handle - can you get it to step and respond ?

Post up a schematic or at least a Fritzing sketch so we know how you have hooked it up

I would particularly like to know what wires you have going to the easydriver (and where)

Are you using a library or driving it directly ?

Craig