Schematic Code

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  #1  
Old 11-27-19, 07:32 PM
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Schematic Code

If an electrical schematic shows a switch (like a rotary mower) in the open position in the drawing, does that necessarily mean that the switch is "normally open"? I have a switch that is missing on an old Toro, that might be able to be replaced by a generic switch, but I need to determine whether the original switch was Normally open, or normally closed. I think the switch is supposed to prevent the engine from starting if the lever is in the MOW position I would think that to do that, that the switch would have to be OPENED (making it normally closed) to break the circuit to the key and starting mower etc. With the deck sitting on the bench, with the deck lever in neutral, the tang would be pushing in the plunger on the switch if there was one in place. At present with the switch gone, and the wires that went to it twisted together, everything starts and runs, but not sure that anything disables the mower for safety purposes, as the entire mower must be drained of fluids and stood on its back to reassemble for a test.
 
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Old 11-27-19, 07:36 PM
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I believe they are normally open. All the switch does is ground out the spark plug so that it stops running.
 
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Old 11-27-19, 08:40 PM
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Most switches have both NO and NC connections.
 
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Old 11-27-19, 08:46 PM
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Schematic Terminology

I really like your tag line Mike (Albert Einstein)

What I can't get my head around is how the removal of a normally open switch and twisting the two wires that go to it together, don't ground everything out right away. (if that was the purpose of the switch) I would think that the logical way to look at it is that since the lever in the neutral position pushes in the plunger. that it should maintain a circuit, not create one. (like to ground) If the circuit is not maintained, the engine shouldnt be able to be started. If I assemble it and then untie the two switch wires, and that will narrow down the possibilities. I would think that if nothing runs with those wires separated, that the switch is normally closed, wouldnt you?
 
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Old 11-27-19, 10:41 PM
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I would think that if nothing runs with those wires separated, that the switch is normally closed, wouldn't you agree?
A schematic doesn't necessarily indicate a normally open or normally closed switch unless it's labeled as such.
 

Last edited by PJmax; 11-28-19 at 10:41 PM. Reason: typo
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Old 11-27-19, 11:28 PM
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I would think that if nothing runs with those wires separated, that the switch is normally closed, wouldnt you?
No. If it was a safety switch it would be normally open so the unit won't run until you press the pedal, sit on seat, etc. and closed the switch.

Sometimes you will find a note on the schematic stating what condition the switches are depicted in.
 
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Old 11-28-19, 11:06 AM
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The object of the game is to buy a generic switch (NO or NC) that will work in this application. Since wiring the switch leads together effectively closes circuit so everything starts and runs (even with the deck lever engaged in the MOW position) I can only assume that it is a normally closed switch was there originally. (when the tang pushes in the switch plunger, It should open the circuit so the mower cant be started in MOW. Im therefore betting on a NC switch is the way to go if I can find one that can be fitted. May be wrong, but have been before. I will post back success or failure!
 
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Old 11-28-19, 11:08 AM
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switches are cheap. IMO your digging too deep. By a switch of each variety. trial and error wins....
 
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Old 11-28-19, 11:12 AM
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Are you still messing with this switch.....


I left you some choices in your original thread.... -toro-safety-switch.html
 
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Old 11-28-19, 12:53 PM
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Post a link to the drawing. You are not being specific enough to know what your drawing is saying.
 
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Old 11-28-19, 08:46 PM
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Schematic

Yes that is the switch that is missing, and I have to replace with something. I think you told me at that time (previous post) that I needed to be careful to specify whether the replacement was NO or NC. I am just trying to do that. the two wires that go to that switch have been twisted together and everything works, but no safety shut off if the mow lever is in in MOW. The plunger on the switch is NOT pushed in when the lever is in the MOW position. (this is counter to what I said in an earlier reply.)
 

Last edited by WML13; 11-28-19 at 08:53 PM. Reason: Terminology
  #12  
Old 11-28-19, 09:28 PM
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I think the switch is supposed to prevent the engine from starting if the lever is in the MOW position
wiring the switch leads together effectively closes circuit so everything starts and runs
The plunger on the switch is NOT pushed in when the lever is in the MOW position
So wires shorted makes it run. Plunger pushed when not in MOW. So a pushed plunger needs to be closed. That means not pushed plunger is open.
That is a normally open switch.
 
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Old 11-29-19, 09:00 AM
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Can't disagree, Now I need to see if the switches in Petes reply earlier can be purchased as normally open and fitted into the bracket that was made for the original. Thank you for the replies!
 
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Old 11-30-19, 05:55 PM
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A samaritan who likes to be a hero dropped off a microswitch that has a plunger and can be wired either NO or NC. I just have to engineer a bracket for it, and this one shouid have a fork in it!
 
 

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