Why is this switch necessary

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Martin B

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Some told me to install the switch in the picture. I'm just wondering if it's even necessary. The circuit feeds 2 electric (120volt) window shades. There is a 120 volt up down switch on the wall. When energized by the momentary switch one wire makes the shades go up the other makes the shades go down. Simple

This contraption makes no sense to me at all. It does not change voltage, hz, it does not rectify or anything. It's like a complicated wire nut.

Can anyone explain why it needs to be installed.

Thank you,
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Are there also individual controls for each blind?

If so, my guess is that it keeps the blind A controls from also moving blind B.

So it might be necessary for individual controls for each blind, and group controls to move them all together.
 
The wiring diagram is available on-line: search for >isolating relay gen-3 by draper<

Looking at the diagram, I'm wondering if it might not be in error-- except the common and ground, I think the switch should take raw 110v and route power to the relay ONLY when the switch is thrown (in either direction). I think the Input power should NOT be routed to the relay!

If the switch is wired as illustrated, I think that throwing it will short either the Red or Black wires to Common-- which should light up the fuse box!

But that's just my thinking.
 
It looks like that board contains the motor run cap. I think the relay is there to disconnect the opposing direction motor wire and force the shade in one direction in the event both inputs (up and down) are energized simultaneously (for example if discreet up/down buttons are used instead of a SPDT center off switch).

The diagram is poor -incoming power would connect to the center terminal of the SPDT switch (or relays on automation controller or what have you), the two outputs from the up/down switch connect to the relay module(s) inputs. Neutral obviously doesn't connect to the switch and is carried through to the relay module inputs.
 
Attached is my suggested wiring.

I am NOT an electrician (but I wire model trains)!

Rewired.jpg
 
I suspect it is there so that if there is more than one switch location, they can't try to open and close the curtain at once, it blocks one of the two inputs when the other is active.
 
This product is designed to be a job site rescue device by allowing multiple motors to be connected to one motor control or switch and provides group control of these motors. Each motor must have its own ISO Relay. Make sure the total FLA of all motors grouped together does not exceed the load carrying capacity of the switch or motor control being used.
Click to expand...

Most likely this is used because;

A) To save space, the motors don't have a starting cap on them so it is in this board, which makes it easier to implement the reversing of the motor. Single phase motors so not naturally reverse. You would typically use a drum switch to move the correct wiring around to the starting capacitor, not a simple changeover switch. That board is taking the place of that drum switch based on the simpler changeover switch they have you use. Otherwise you would need to have a two motors to reverse it with one switch.

And/or B) The board has a current sensor that cuts power off when the motor stalls at either end of the shade travel, because again to save space, there is no end-of-travel limit switch (at either end) on the sha. If you didn't have this and wired one shade, it might be fine so long as the user ALWAYS knows to let go of the switch when it reaches the end of travel. But have you even seen a kid find something like this? Guaranteed they will hold that switch until the motor catches on fire. then if you have multiple shades, each one might reach the end of travel at a different time than another one, so that would FORCE you to hold the switch longer, stressing the motors on the ones that have already finished. This board cuts off each one individually when they are done, no matter how long you hold the switch.
 
Todd0x1 said:
It looks like that board contains the motor run cap. I think the relay is there to disconnect the opposing direction motor wire and force the shade in one direction in the event both inputs (up and down) are energized simultaneously (for example if discreet up/down buttons are used instead of a SPDT center off switch).

The diagram is poor -incoming power would connect to the center terminal of the SPDT switch (or relays on automation controller or what have you), the two outputs from the up/down switch connect to the relay module(s) inputs. Neutral obviously doesn't connect to the switch and is carried through to the relay module inputs.
Click to expand...

That cap is used as "capacitive dropper" as part of the relay's power supply (the relay reads 24VDC).

The chip near the relay seems like an op amp (not sure by just looking at the pic), speculation: maybe there's shunt current sensor on the other side of the circuit board, the op amp amplifies the current sensed, if the current exceeds certain point, it opens the relay contacts regardless of the switch position.
 
Martin B said:
Some told me to install the switch in the picture. I'm just wondering if it's even necessary. The circuit feeds 2 electric (120volt) window shades. There is a 120 volt up down switch on the wall. When energized by the momentary switch one wire makes the shades go up the other makes the shades go down. Simple

This contraption makes no sense to me at all. It does not change voltage, hz, it does not rectify or anything. It's like a complicated wire nut.

Can anyone explain why it needs to be installed.

Thank you,

Sent from my Pixel 2 using Tapatalk
Click to expand...
I think you maybe confused, the up down switch you mentioned on the wall is the same switch you are questioning the need for, I think.
 
Hello Kwired,

No I understand the wall switch. It just seemed to me that the device I took a picture of didn't really do anything. I have installed line voltage switches for electric projector screens before and I did not realize the 120 volt motors had other components in them to make the turn in a different direction.

All of the replys to my post where really great. Thanks!

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Martin B said:
Hello Kwired,

No I understand the wall switch. It just seemed to me that the device I took a picture of didn't really do anything. I have installed line voltage switches for electric projector screens before and I did not realize the 120 volt motors had other components in them to make the turn in a different direction.

All of the replys to my post where really great. Thanks!

Sent from my Pixel 2 using Tapatalk
Click to expand...
Looks like it contains the capacitor instead of being on board in the motor, that is very important to making the motor work properly even if there were nothing else on the board.
 
r6680jc said:
That cap is used as "capacitive dropper" as part of the relay's power supply (the relay reads 24VDC).

The chip near the relay seems like an op amp (not sure by just looking at the pic), speculation: maybe there's shunt current sensor on the other side of the circuit board, the op amp amplifies the current sensed, if the current exceeds certain point, it opens the relay contacts regardless of the switch position.
Click to expand...

Ah ok. Thanks for clearing that up.
 
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