Instructables
Picture of Homebrew Magnetic Motor Starter

This is one of those things that I always wanted, and wanted to do besides. Well now I have it, and have done it too. I will share how I managed to do it with you in this article if you bear with me for a bit.
 
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Step 1: My Motivation

Picture of My Motivation

When I got this saw it had no motor or switch. I put a motor on it and rigged up a switch using a scrap circuit breaker. That setup was hardly ideal but I said to myself while I was doing it this is temporary, all the while also thinking is this going to be temporarily permanent? We all know how those temporary things can go don't we?

I used that switch and it worked, but every time I flipped it all I could hear in my head was my inner voice echoing, "this is temporary ..." Stuff like that can really throw me off my game let me tell you. I wanted my push button start and stop buttons!
raheen was trying to follow JIC convention.  Remember, just because something works, doesn't make it right.  There are a few things missing that should be discussed:
The drawing doesn't show but your panel and motor must be grounded.
Does this motor starter have an overload heater w/N.C. contact?  If so, this contact should be wired in series with your 'Stop' button. 

Does your motor have a 'reset' button or an internal thermal switch?

We usually show the transformer at the top of the drawing with a small fuse on the secondary LH line (L1).  The RH line (L2) is normally grounded to the panel (in case the transformer shorts across to the sec. side).  (So far we protected the transformer, the relays and the internal wiring.)

Plugs and receptacles are disconnects and should be used on the MOTOR cord for operation and ease of maintenance.  In fact, consider using three different receptacles on your control panel (one for each device).  An "on" LED should show your contactor is energized.  The only other 'improvement' might be a raised (off the bottom) terminal strip.
pfred2 (author)  simplyconnected1 year ago
Thanks, I'll remember that. Just because something works ...
raheen3 years ago
There is an error in your circuit diagram.
It should look like this for non-latching push-buttons.
Start-Stop_circuit.bmp
pfred2 (author)  raheen3 years ago
Thank you for the different schematic. Maybe you can explain to me what the advantage to your circuit is? Also why you say mine has an error. Because mine does in fact work fine here.
rtarvin pfred23 years ago
Don't know if you ever got your answer from raheen. But this a common Circuit used in commercial application. on his diagram is a 2 push button switch. when pushing the on button activates latching relay. if you look at the line between switch circuit and the out circuit to relays. cause a continuous Circuit unit broken by the off push button.
pfred2 (author)  rtarvin1 year ago
The common circuit uses the same voltage for the coil as is being switched. Using different coil, and switched voltages is less common. Uncommon enough that I did not find a single schematic depicting it in over 30 pages of search engine links. Believe me, I looked! I wasted more time looking than it took me to design this circuit myself in fact. I always prefer to use professionally designed circuits over my own. I figure perhaps the pros know more than I do so I might as well avail myself. In this case they were all mute though.

Since I've posted this the pros have come out of the woodwork to criticize what I've done. Too bad for them what I've done still works flawlessly to this day though. Duh, winning!
LaserDave2 years ago
Nifty idea. The description is mostly story (and fairly lengthy), maybe a tiny more focus on the topic and a little less life-story would turn your good instructable to a great one.

Good job.
pfred2 (author)  LaserDave2 years ago
This article was featured so I suppose it meets this site's criteria. As rtarvin points out in their comment, "this a common Circuit used in commercial application.", so it isn't my nifty idea, just my build of it. I was surprised I couldn't find a suitable schematic online, which is what prompted me to post my article. Now I know there is a schematic online of this particular kind of contactor.
UATradition3 years ago
I enjoyed this one. This is precisely the type of thing that I love spending weekends with my father doing in his shop. It seems he always finds little projects like this to make the "barn" better !! Looks good !
rimar20003 years ago
How a great work!
pfred2 (author)  rimar20003 years ago
Thank you. Liked that one did you? I've been like a little kid pressing the buttons. The this is temporary voice in my head he is gone now too! But now it says I must make something great on the machine.
If "Liked that one did you?" means "is it similar to one you did?" the answer is "no, I would not be able to make a thing like that." I am too lazy to learn electronics at my age. Simple things like a bridge rectifier or something like that, I am encouraged, but not much else.