power windor sensor..

[manz]

does anybody know how does the circuit of the power window knows that the window is already fully opened or fully closed (cut-off switch). i`ve read how power windows work but just couldn`t really find the answer for it..

here`s the situation:

if u pressed (full) the button for the window to open, even after u release your fingger from the button,the window will still go down..

untill it reached its limit (fully opened), theres a sound (seem like a relay de-energize) and all the flow to the power window motor being cuts off.

the question is:

1. does anyone knows how the circuit can detect that the window had fully opened or fully closed??

2. is there a circuit that to measure the flow or voltage of a system(dc motor) that is to cut of the current supply if there`s too much load for the motor??

i`m so sure that there`s no mechanical switch used in the system. it is some sort of circuit that detact the current or something? is there any posibble way to do so (cut the current if there`s to much load for the dc-motor)

thanks guys...

 

[zevon8]

Some are simply a bimetallic strip that opens like a circuit breaker when the motor stalls at the end of travel. The bimetal switch is in one set of connections ahead of the reversing relay, so that the window can be reversed, even when the switch has opened for the other direction.

These motors draw fairly large currents when stalled, the common Bosch ones draw about 5 amps running, over 25 when stalled.

Some are more sophisticated, using an electronic control to shut off power when the current rises.

 

[eblc1388]

Some are simply a bimetallic strip that opens like a circuit breaker when the motor stalls at the end of travel.

So far so good. But what happens after the current is cut and the bi-metallic strip cool down and re-make the contact? So I guess it is more like a limit switch instead.

However, using limit switch has the disadvantage of chopping people's hand or head off should they happen to be in the path of the closing pane.

 

[manz]

thanks for the info...

if that so, how can i find all these switches, what are the parts called or what are the code no for that(you know like transistor- 2n3904 or sumthing)or maybe there is a circuit to measured the current flow and de-activate the self anegizing relay..

is there such a thing called retractable fuse? i think i can use that also for the same purpose, that is to cuts off the current after the motor had stall.

ok here is what i`m doing..i made a system (simple circuit) attached to my power window motor. any time if the car is locked(the siren sounded), all my window will automatically closed,so i didn`t have to closed my window with the normal way(pressed the switch).it`s realy cool :lol: the window will closed by itself but i have to put the push button switch on top of the power window linkage to indicate the window had fully closed.the simple circuit is that a self anegizing relays that being activated each time there`s a current flow to the siren..i even put the 10A fuse to the system incase there`s anything goes wrong.. the problem is that to mount the bracket for the limit switch to the linkage..it takes quite sometime to properly measured and attach the bracket to the linkage..so i`m hopping there is such a circuit that can replace these limit switch at the linkage so its easier and faster to mount it.

can anyone give opinion about that also...

thanks..

 

[zevon8]

Some are simply a bimetallic strip that opens like a circuit breaker when the motor stalls at the end of travel.

So far so good. But what happens after the current is cut and the bi-metallic strip cool down and re-make the contact? So I guess it is more like a limit switch instead.

However, using limit switch has the disadvantage of chopping people's hand or head off should they happen to be in the path of the closing pane.

The idea is to have the bimetal open if someone holds the up/down switch too long. If they are still holding it when the bimetal closes again, it will either quickly re-open since it is still a little warm, or the fuse may blow.

The Bosch motors also have a bimetal switch on the motor leads, so that can also open. If the motor gets hot enough to trip this one, there is enough hot metal mass in the casing to keep the switch open for several minutes.

As an aside, these motors are very cheaply made, with large variations in current draw. This requires a fairly crude "brute-force" protection design.