I need to buy a motor for a automated blinds project. Pulling down on a fish scale attached to the blinds, I got a read of 3.5kg (I believe this means 34.32 newtons was necessary). The drum diameter is 4.5m.

I'm wondering how much torque I need for a motor to effectively open the blinds.

Here's an image for reference

And a link to the project: https://github.com/vietquocnguyen/NodeMCU-ESP8266-Servo-Smart-Blinds

## Best Answer

Torque is equal to the force applied times the distance of the force from the axis of rotation: $\tau = F\times r.$ Plugging in your numbers ($F = 34.32N$ and $r = 2.25 cm$, the radius of your drum), I get a torque of 77 N-cm or 0.77 N-m (newton-meters).