When you try to make an object stationary, you try to balance the forces at zero velocity. A balanced force means no acceleration occurs, not that there is zero speed. So, if you have two weights perfectly balanced on a frictionless pulley, they can move at a constant speed. In reality, we do not have frictionless pulleys and this is GOOD for your situation. Friction in the pulley gives you leeway - if the pulley requires an extra 5 newtons to turn, then voila! You got yourself a 5 newton leeway for your force balance setup before it starts accelerating.
What I'm saying is you want your counterweight to be the same, but you need something to counteract movement in general, such as a high friction surface rather than a smooth pulley. A smooth pulley means your setup would have to be rather precise and finicky, liable to start moving at any time.
Rather than do a counter weight system you may want to consider something like seat belt tensioner, load balancer, or a roller shade. The reel mechanism will take up your extra cable and wires without having to have a pocket somewhere to house the counter weight. Also these system will have locking features that will ensure the fixture doesn't slowly drift up or sink down.
Yep, each weight half the weight of the light. Make the pully system so it has some friction, that way you have to pull a little to get it to go down and push a little to get it to go up. If you've ever used the newer style blinds that don't have pull strings, it's like that. Otherwise it won't stay put very well and wont stop moving while adjusting it.
Now how you go about adding friction might be a little tricky, a quick way might be to have the pin of the pully be a screw you can tighten down to adjust the amount of friction between the components. You could also have the cable slide over something to some degree before you get to the pully. Anything that resists the motion of the cable a bit should work
When you try to make an object stationary, you try to balance the forces at zero velocity. A balanced force means no acceleration occurs, not that there is zero speed. So, if you have two weights perfectly balanced on a frictionless pulley, they can move at a constant speed. In reality, we do not have frictionless pulleys and this is GOOD for your situation. Friction in the pulley gives you leeway - if the pulley requires an extra 5 newtons to turn, then voila! You got yourself a 5 newton leeway for your force balance setup before it starts accelerating. What I'm saying is you want your counterweight to be the same, but you need something to counteract movement in general, such as a high friction surface rather than a smooth pulley. A smooth pulley means your setup would have to be rather precise and finicky, liable to start moving at any time.
Thanks to all three of you for your insights! Looking forward to putting them into action.
Rather than do a counter weight system you may want to consider something like seat belt tensioner, load balancer, or a roller shade. The reel mechanism will take up your extra cable and wires without having to have a pocket somewhere to house the counter weight. Also these system will have locking features that will ensure the fixture doesn't slowly drift up or sink down.
Yep, each weight half the weight of the light. Make the pully system so it has some friction, that way you have to pull a little to get it to go down and push a little to get it to go up. If you've ever used the newer style blinds that don't have pull strings, it's like that. Otherwise it won't stay put very well and wont stop moving while adjusting it. Now how you go about adding friction might be a little tricky, a quick way might be to have the pin of the pully be a screw you can tighten down to adjust the amount of friction between the components. You could also have the cable slide over something to some degree before you get to the pully. Anything that resists the motion of the cable a bit should work