How to keep stepper motor from moving when off

I have this project where I want to have a motor driving a vertical sprocket/chain. There are paddles on the chain which hold stuff and the project is essentially a dispenser. I wonder when the product starts dispensing that the weight on one side of the chain will be different than the weight on the other side of the chain. The weight difference might be about 1-2 pounds. I worry that this might move the motor shaft when the motor is off. I was going to use a stepper motor so that I could precisely dispense the product. I don’t want to keep the motor on all the time. Is there some device I can add to my system to keep the motor from spinning after I remove power from it?

A worm gear drive will usually prevent motion when the motor is powered off.

Thanks - I thought of using a worm gear but then I wondered if the speed would be too slow. I suppose I could add gears to the worm wheel to speed it up again.

Also, I give up the flexibility of going in reverse, but that’s probably not an issue here.

It really depends on what motor you’re using. It would be lifting 1-2 lbs, would need a significant motor so maybe the motor would have enough resistance to hold the weight. I would experiment with this then if it needed something to hold it, then I would add it in.

A worm gear arrangement would be my first thought also but after that … perhaps some form of ratcheting that could be engaged/disengaged ?

Spring loaded solenoid with a shaft that pinches the sprocket when off. Apply power, spring loaded shaft retracts.

Kinda like air brakes…without the air…or the brake pads…or the truck…

Ok, nothing like air brakes…