Shopsmith Forums

A couple of weeks ago, after I absent-mindedly left my 10ER plugged in while I did maintenance on it, including pulling the variable speed changer apart to clean and lubricate it, I decided to look for a safer way to handle the power to the machine. I had also wanted to add an emergency cutoff switch, and to place the power switch in a more convenient, and safer location when using the 10ER as a table saw. It looked like using a magnetic power switch with an emergency cutoff button might be the solution, but I was not sure if the power off button completely removed power like the emergency button did.

I got the Powertec 120v Magnetic Switch and a surface mount two-outlet box, connected them with a 1/2” electrical tube, and mounted them on a small piece of 3/4” plywood, so I could move the switches outlet box to wherever I need it. I also got a 25’ heavy duty extension cord, that used 12 gauge stranded wire (because the switch called for stranded), and cut and stripped sections from it to use as jumpers within the switch and between it and the outlet, making sure to connect ground to both the outlets and the metal box.

It works perfectly. I tested with my volt meter to confirm there is no voltage to the outlets, no matter if you use the emergency cutoff button or the red power off button. One of the safety features of this switch is that if you lose source power the emergency cutoff switch relay is triggered, so that when the power is restored you have to push and twist the emergency switch to re-engage it so that power will then be reapplied to the input of the on/off switch. Until you do that the on/off switch is not functional. This prevents you from walking off and forgetting that your machine is still on after losing power. That could be a disaster if you forgot to turn your router or table saw off after losing power.

One of the things I can do with my new power setup is have both my machine and vacuum plugged into the outlets, so they will both start up when I push the green power button. I can move it from one wall location to another, or to my bench when I want to use it to power my router. And now I don’t have to worry about leaving my ShopSmith plugged in as there will not be any power applied to the toggle switch. It’s much more convenient, not to mention safer, to power off when using the table saw. And, god forbid, if some emergency happens in the shop, someone else can easily power off the equipment if I’m lying on the floor. As much as I want to avoid that, I do like being prepared for all possiblities.

Here’s a shot of my setup, and of the Powertec wiring schematic. Note that in the schematic, the outlet is connected where the machine is indicated.

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I've had these on my 10ERs and my mark VII for several years. Mine are mounted directly to the machine. and work like a charm. And I don't have to worry about restarts after power restoration. And an easy emergency stop buttom.

Question is, WHAT is between terminals 13,14 and 23,24?

like!

JPG wrote: ↑Sun Jul 11, 2021 9:52 pm Question is, WHAT is between terminals 13,14 and 23,24?

Good question, I wondered the same thing. Fortunately, the switches had details about their internals printed on them. The Emergency Stop Switch has two sets of contacts controlled by the “button”. Pins 1 & 2 are normally closed, and pins 3/4 are normally opened, and in this configuration only pins 1 & 2 are used, which controls the hot power lead. When you press the Emergency Stop Button, it mechanically trips the switch, opening the contacts between pins 1 & 2, thereby removing power from pin 23 on the On/Off Switch. If you lose source power, the Emergency Cutoff Switch electrically trips the normally closed contacts between pins 1 & 2 (I assume this is done magnetically). If this switch is tripped by either pressing the emergency button or by losing source power, you have to manually push and turn the button to close the pins 1/2 contacts, returning power to pin 23 of the On/Off Switch.

The On/Off Switch has a relay connected between pins 13 & 23, so when the Emergency Cutoff Switch removes power to pin 23 the relay opens deactivating the On/Off Switch. When the On/Off Switch is deactivated you can physically feel it has been disabled, when the switch is active you can hear it click when you press On or Off, there is no click when the switch is disabled.

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So it has BOTH a mechanically/manually opened panic switch AND has a power lock out relay?

Yes. A loss of power both triggers the Emergency Cutoff Switch, magnetically(?) opening the Normally Closed contacts of the switch, and the On/Off Switch’s relay recognizes lost power on its input side, disabling that switch. Either way the Emergency Cutoff Switch is triggered, whether manually or electrically, you have to manually push and turn the big red button to reset that switch (close the contacts). At that point Power is reapplied to the input of the On/Off Switch and you can use the Green power button to turn things on.

I like the double safety.

I assume in addition to the relay, there is a solenoid that is energized as long as power is available that holds the emergency off(red button) latched 'on'. Assumption!!!

JPG wrote: ↑Mon Jul 12, 2021 12:17 pm I assume in addition to the relay, there is a solenoid that is energized as long as power is available that holds the emergency off(red button) latched 'on'. Assumption!!!

I assume that is the “magnetic” action within the Emergency Cutoff Switch, but there is no schematic symbols on that switch, just labeling for the Normally Open and Normally Closed contacts, but that is how it acts.

I didn’t think to take photos while I had it open.