# Float switch logic diagram help for apprenticeship



## identity710 (Feb 8, 2019)

Hey guys, Just started my motor term for local 48 apprenticeship. Got an assignment to try our hand at making a logic diagram as a "see what you know" type situation. I'm hoping if I could see this drawn out, it might make some sense to me and it could help me figure the rest out. The lab is as follows:

A tank is used for a washdown process and needs to fill when almost empty. Occasionally, the tank will need to be filled completely before washing a particularly large batch of product, so the customer has asked for a manual fill option.
Design a circuit that allows the user to choose between a manual start (Hand) or automatic operation (Auto).
The automatic feature will be two float switches that control the level of a tank.
Choosing the hand option will start the motor immediately but still shut off before the tank overfills.

The parts list is a NEMA Motor Starter, a Hand-Off-Auto Switch and two (2) limit switches.



How would you guys tackle this?


----------



## splatz (May 23, 2015)

identity710 said:


> Hey guys, Just started my motor term for local 48 apprenticeship. Got an assignment to try our hand at making a logic diagram as a "see what you know" type situation...
> 
> How would you guys tackle this?


I'd just ask the internet to do it for me, thinking is for suckers, and learning is so 2007.


----------



## identity710 (Feb 8, 2019)

You don't think I've tried my hand at this already? We haven't gone over this stuff yet, and the only thing the instructor tells me is that it's wrong and we'll go over it in class. I'm just trying to get a heads up and get a better understanding. No need to be a child. Kids can be petty. I thought by explaining myself on a forum of people that, in my mind are usually supportive, that I might get feedback. Instead I found someone who requires a diaper change.


----------



## MikeFL (Apr 16, 2016)

We're not going to do your homework for you.
You did not mention in the OP that you tried and instructor said it's wrong.
Your post implies you want us to do your homework.

Show us (or describe) what you drew up and why you did it that way.


----------



## Cow (Jan 16, 2008)

Draw something out on piece of paper and take a pic of it and post it. Even if you think it's wrong.



You have to at least show us what you've got.


I learned the hard way, I did not have the internet to solve everything for me. It can be done. Even nowadays. 



Show some initiative, let's see what you've got so far....


----------



## identity710 (Feb 8, 2019)

Yeah, I'm on site right now.

I'll definitely put it up as soon as I'm with it again.

Thank you to the lot who gives constructive feedback.


----------



## John Valdes (May 17, 2007)

You can find a simple 3 wire motor control circuit on the internet.
Find a start/stop diagram and edit it to your application.

Can you draw a start/stop/jog on paper without any help? If no, you need to understand how a motor control circuit works before you can take it to your application.

Maybe your instructor just wants to see how much your class does not know. So he knows where to start teaching.


----------



## Wirenuting (Sep 12, 2010)

identity710 said:


> You don't think I've tried my hand at this already? We haven't gone over this stuff yet, and the only thing the instructor tells me is that it's wrong and we'll go over it in class. I'm just trying to get a heads up and get a better understanding. No need to be a child. Kids can be petty. I thought by explaining myself on a forum of people that, in my mind are usually supportive, that I might get feedback. Instead I found someone who requires a diaper change.


Welcome to ET
Please finish filling out your profile. 

We are here to help and not do for you. 
No need to be snarky with your diaper change comment. It makes you sound so little and childish.


----------



## telsa (May 22, 2015)

To the OP: presenting your teacher with false knowledge is a TERRIBLE idea.

The smart play is to come back with the wrong solution.

He'll love you for it.

HE, not this forum, is supposed to be the fount of knowledge.


----------



## identity710 (Feb 8, 2019)

Guys, guys guys....

I am not presenting anything I don't know about. That is why I am asking for help. I understand some of the concepts, i just want to feel prepared and ready to accomplish the task at hand. Are you telling me that no one does research on their own? I have done some research and I am reaching out to get some help. I drew out a logic ladder for float switches, I am just not sure how to make the necessary changes to get it to do what I am wanting. Additionally, my comments seem to have been edited (thanks moderators, I apologize) but I wasn't giving out anything I wasn't being dealt.

Here is the drawing I have so far, and I am just looking for guidance.


----------



## identity710 (Feb 8, 2019)

Sorry, hopefully this one works (Not sure what format to upload the images in)

https://i.ibb.co/BGfxCmd/Sketch.png

Found out it is because I don't have enough posts.


----------



## gpop (May 14, 2018)

Simple drawing of a lift station which is reverse of what you wanted but the idea is the same so just change the logic.












I suck at paint


----------



## glen1971 (Oct 10, 2012)

gpop said:


> Simple drawing of a lift station which is reverse of what you wanted but the idea is the same so just change the logic.
> 
> 
> View attachment 132246
> ...



The OP said the high level must shut it down in manual as well. So it should be wired the HOA first, then the auto string should have the low level switch NC wired in parallel with the holding contacts, to form a "start" piece of logic. Then there should be a NC high level switch (stop) for the high and finally the coil. The Hand wire off the HOA should go between the start and the stop switches. If the tank is empty, both are closed and the pump will start in Auto. When the level rises the low level switch will open, but the pump will still run with the holding contacts. When the tank is full, the high level switch opens and the pump stops. In Auto, as the level drops the high level switch will close and the low level switch will stay open and the pump won't run until it hits the low level. In Manual, or Hand, the pump will run on the high level switch and the tank will stay as full as possible, or the range on the float of the high level switch.


----------



## B-Nabs (Jun 4, 2014)

....


----------



## splatz (May 23, 2015)

I think the OP's sketch is fine. Maybe he's OK after all. 

You want the high float to open in any event so high float NC is in series with everything. 

The Hand and Auto are in parallel; hand goes straight through to the high float NC. 

The Auto is in series with the low switch NC so it starts when the low float floats, but it must be latched with the relay NO contact, or it will only fill briefly until the low float floats again.


----------



## John Valdes (May 17, 2007)

Welcome to Electrician Talk 710.
Thanks for taking the time to fill out your profile.


----------



## gpop (May 14, 2018)

splatz said:


> I think the OP's sketch is fine. Maybe he's OK after all.
> 
> You want the high float to open in any event so high float NC is in series with everything.
> 
> ...


Instructor will still reject the OP drawing as he didn't state that the N/O was a Aux. Generally rule is anything that is not labeled fails. (I know on a simple diagram that may seem unfair but add a few relays where you have a lot of No/Nc contacts it makes sense to label)


----------

