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Remote power switch for mustard

J

justaccord

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Nov 5, 2007
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Powermatic 3520b owners: Three questions:

1. How essential do you find remote power switch when turning over the bed? I.e., does safety require a switch mounted at the tailstock end?

2. Where and how do you mount the remote switch?

3. Is there any reason I couldn't just make a switched 220 box, plug the lathe cord into it and use that as a remote instead of messing with factory wiring?

TIA

Dave Rudy
 
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Pm3520b

Hi,
I bought the remote with my 3520 because I knew that at some point in time I would turn something at the tailstock end of the lathe, and I wanted to be able to do that without walking back and forth. Not to mention any safety issues. Even if you do turn in the standard position, some hollowforms and swan's neck tools are easier to use from the back of the lathe, and then again, it's nice to have a switch with you. It comes stock with a magnetic pad on the back so you can position it anywhere.
I wouldn't suggest interrupting the line voltage, because then the inverter wants to reset itself each time. The PM remote simply provides some internal power interrupt.:)
Kurt
-----
 
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remote

I also bought the PM supplied remote,works great when turning from tailstok end. Go to web site for Mustard Monster there is a home built remote there. George
 
OK, I went to the mustard monster site (thanks, should have thought of that first) and found the two versions of self-built remote switch.

I am somewhat electrically challenged. I can definitely manage building the switch box, if someone would be kind enough to tell me what gauge wire should be used, and how to wire it into the main power switch.

Thanks
 
justaccord said:
OK, I went to the mustard monster site (thanks, should have thought of that first) and found the two versions of self-built remote switch.

I am somewhat electrically challenged. I can definitely manage building the switch box, if someone would be kind enough to tell me what gauge wire should be used, and how to wire it into the main power switch.

Thanks
Click to expand...

One simple way of wiring in an additional shut-off switch would be to just wire it in SERIES with the existing shut-off switch (that would be the red mushroom switch). I recommend getting another red mushroom switch so that its function is clearly understood. Also, it is easier to actuate in the correct direction than using a toggle.


In any case, DO NOT wire it into the main power side of the line! As Kurt stated above, the controller will lose its mind if you turn it off by just shutting off the main power. It would be essentially the same thing as shutting off your computer by yanking the power cord rather than going through the shut down procedure first.

BTW, what is the web site for Mustard Monster?
 
It's essential to me

as I found out when dust killed it and I had to do without. Not only for hollow forms and working off the end of the lathe, but it is nearly required when doing large square bowls. Reaching around that propeller is a wake up. I would like to have a speed adjustment as well. I like being able to hit the switch with my hip in tricky situations. Keep your switch in a sandwich bag or inevitably the dust will get it! As the Mustard Site covers cheap replacement switches are available from Grizzly and also John Lucas outlines a repair process that works sometimes. Also unless you have more time than money the PM switch isn't a bad buy with all the cord, magnet and box. You can use up a lot of gas and lost turning time scrounging for the parts to make your own. $0.02
 
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That controller doesn't have provisions for a second pot to be used as a speed controller. There are only three ways of adjusting speed on that controller: keypad input, pot input, and programmed-in fixed speeds (that would be essentially the same as a stepped cone pulley drive). The controller is probably not set up to allow the first and third options without changing the programming. Changing the programming might require entering a passkey (if Powermatic has it locked).

Your best option would be to remove the pot from the headstock and install it in a box with a magnetic base so that it could be moved to different locations.

For the uninitiated: this type of work, if done correctly, involves a lot more than merely connecting wires together. Making the design adequately rugged needs to be considered. Also, proper engineering practice dictates that the design needs to be made fail-safe. For those who don't understand the term "fail-safe", let me explain that it does NOT mean that it can't fail. What it DOES mean is that WHEN it DOES fail, that the operation will revert to a known safe condition (such as shutting down). Without designing the system to be fail-safe, it would be possible for a failure to result in the lathe going to maximum speed. If you don't know how to do this, then ... duh ... don't do it!
 
I believe the problem many are running into is not dust in the contacts, but carbon build-up by using contacts that are not rated for DC. DC actually carbons up contacts much faster than AC and the switch will fail with the same symptoms that everyone is explaining away as "dust". This includes the Grizzly switches and other residential type switches. I built my remote e-stop from parts ordered from McMaster-Carr for about $40 (except for the chunk of wood and the magnets). The biggest cost is the switch itself (M-C #7546K25), which has contacts rated for 2.5 amps @ 24VDC.
 

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jbiddle said:
I believe the problem many are running into is not dust in the contacts, but carbon build-up by using contacts that are not rated for DC. DC actually carbons up contacts much faster than AC and the switch will fail with the same symptoms that everyone is explaining away as "dust". This includes the Grizzly switches and other residential type switches. I built my remote e-stop from parts ordered from McMaster-Carr for about $40 (except for the chunk of wood and the magnets). The biggest cost is the switch itself (M-C #7546K25), which has contacts rated for 2.5 amps @ 24VDC.
Click to expand...

DC "carbons" up contacts faster than AC? Really? What is the mechanism for this phenomenon? And where would this "carbon" be coming from?
 
boehme said:
DC "carbons" up contacts faster than AC? Really? What is the mechanism for this phenomenon? And where would this "carbon" be coming from?
Click to expand...
Sorry, I shouldn't have tried to pass that off in one line. The actual failures are not from "carbon" but usually from:
a) excessive corrosion of the contacts from the arc superheating the surrounding air. (The reason I used the word carbon is that we used to describe the corrosion as being similar to the effect of carbon brushes on DC motors before learning the real causes),
b) loss of material from excessive erosion of the contact from overly severe and long durations of the arc, or
c) a crater and spike condition where molten contact material flows from one contact to the other; also resulting from overly severe and long durations of the arcwith current flows in one direction.

The reason that DC contacts typically fail sooner than AC contacts is the self-extinguishing tendency of an AC arc across an air gap. Because the AC current actually stops and reverses direction 120 times per second, there are many opportunities for the ionized air of an arc to lose enough temperature to stop conducting current, to the point where the arc will not re-start on the next voltage peak. DC, on the other hand, is a continuous, uninterrupted flow of electrons which tends to maintain an arc across an air gap much better. Take a look at the contact ratings of a switch, starter, or contactor the next time you pick one up. If the contacts are not rated for DC, chances are it will fail prematurely if used on a DC circuit. If the contacts are rated for DC, the DC rating will be labeled and it will almost always be quite a bit less than the AC rating. Sorry, I didn't mean to ramble.
 
Much of the black color that is seen on badly pitted contacts is oxidation. While carbon is a good conductor (as in carbon brushes), metal oxides are usually good insulators. Where motors are concerned, the greatest amount of arcing occurs during the break phase of switch operation and not the make phase. This happens because motors are inductive loads and the current builds up slowly during make. During break, the existing energy in the magnetic field is dissipated through the contacts as the field collapses. Whether it is AC or DC makes very little difference as the collapsing magnetic field produces approximately the same waveform through the contacts. However, the pitting on an AC motor will tend to be more symmetrical. Once the air around a set of contacts becomes ionized from arcing over, it is very easy for the arc to reestablish itself even at low voltages.

Bill
 
Practically Speaking...

...is there really a lot of high energy arcing in a switch that is in the control circuit for the ON-OFF function on the 3520? It wouldn't seem to be a place where significant arcing will occur.

I was under the impression that the remote switch, or the ON-OFF switch, is in a low voltage circuit and I don't even know if it an AC or DC circuit.

I am using a regular household AC wall type paddle switch, covered in a plastic sandwich bag, and it has been doing well for about a year. I got the idea from Darrell Feltmate and adapted his application to the 3520.

I think the sandwich bag is providing more protection from the dust that any arcing problem that might be lurking.

However, I am not an EE or rocket scientist so it is only conjecture on my part.

Clem
 
boehme said:
Much of the black color that is seen on badly pitted contacts is oxidation. While carbon is a good conductor (as in carbon brushes), metal oxides are usually good insulators. Where motors are concerned, the greatest amount of arcing occurs during the break phase of switch operation and not the make phase. This happens because motors are inductive loads and the current builds up slowly during make. During break, the existing energy in the magnetic field is dissipated through the contacts as the field collapses. Whether it is AC or DC makes very little difference as the collapsing magnetic field produces approximately the same waveform through the contacts. However, the pitting on an AC motor will tend to be more symmetrical. Once the air around a set of contacts becomes ionized from arcing over, it is very easy for the arc to reestablish itself even at low voltages.

Bill
Click to expand...
You're assuming that a switched contact in a static DC control circuit breaks as quickly as the contacts in a dynamic DC motor circuit. That is true only if that speed is designed into the contact/switch itself. The problem with many switches is that the break phase of the contact are an order of magnitude slower in operation, leaving the arc established for a much longer duration. Many switches or contacts that are rated for DC are designed with an auxillary spring (or other similarly functioning design) to open the circuit much more quickly (in effect, to approach the AC waveform you mention). It doesn't sound like we're too far apart in our analysis Bill.

...is there really a lot of high energy arcing in a switch that is in the control circuit for the ON-OFF function on the 3520? It wouldn't seem to be a place where significant arcing will occur.

I was under the impression that the remote switch, or the ON-OFF switch, is in a low voltage circuit and I don't even know if it an AC or DC circuit.

I am using a regular household AC wall type paddle switch, covered in a plastic sandwich bag, and it has been doing well for about a year. I got the idea from Darrell Feltmate and adapted his application to the 3520.

I think the sandwich bag is providing more protection from the dust that any arcing problem that might be lurking.

However, I am not an EE or rocket scientist so it is only conjecture on my part.
Click to expand...

Although arcing takes place in both high and low voltage circuits, whether or not the switch failures are from dust or contact failure is pure conjecture on my part. I've also never verified the information from PM that this circuit is actually DC, as I was told, instead of low voltage AC. I've seen this type of contact failure quite often in the past on DC circuits and decided to design around it for my remote. Who knows, my setup may fail faster than everyone elses because it really is dust causing the problem! But, even if I'm right, you're solution is certainly less expensive and your switch can be replaced several times before approaching the cost of my solution.
 
Clem Wixted said:
...is there really a lot of high energy arcing in a switch that is in the control circuit for the ON-OFF function on the 3520? It wouldn't seem to be a place where significant arcing will occur.

I was under the impression that the remote switch, or the ON-OFF switch, is in a low voltage circuit and I don't even know if it an AC or DC circuit.

I am using a regular household AC wall type paddle switch, covered in a plastic sandwich bag, and it has been doing well for about a year. I got the idea from Darrell Feltmate and adapted his application to the 3520.

I think the sandwich bag is providing more protection from the dust that any arcing problem that might be lurking.

However, I am not an EE or rocket scientist so it is only conjecture on my part.

Clem
Click to expand...

Very good point, Clem. I think that the discussion got sidetracked onto switches that are handling large currents which would be used for a motor operating directly from the power line. The switch on the Powermatic is essentially switching what is known as a "dry" circuit, which means that it is just providing a logic input to the controller and the current is on the order of magnitude of a milliampere. However, there is another type of problem that crops up when switching dry circuits. If the switch is not specifically designed for dry circuits, the contacts can develop a high resistance when closed due to oxidation. It has been quite a few years since I did any design in that area, but I seem to recall that at least some dry circuit switches used what is know as bifurcated contacts that wipe the contact surface clean to maintain low electrical resistance.

I would say that the switch used as the shutoff switch probably is not designed to work in a dry configuration, so it may possibly be developing high resistance.
 
boehme said:
I would say that the switch used as the shutoff switch probably is not designed to work in a dry configuration, so it may possibly be developing high resistance.
Click to expand...

Is there a coating or the like which can be used to prevent the increase in resistance? I have a 15 Amp 110V paddle switch I am planning to install.

If there is not a reasonable preventive measure for a standard AC switch, can someone recommend a good switch for a dry circuit which can be switched off using a hip, knee, etc?

Thanks!
 
KEW said:
Is there a coating or the like which can be used to prevent the increase in resistance? I have a 15 Amp 110V paddle switch I am planning to install.

If there is not a reasonable preventive measure for a standard AC switch, can someone recommend a good switch for a dry circuit which can be switched off using a hip, knee, etc?

Thanks!
Click to expand...

Unfortunately, there is no magic coating or anything else that can "convert" an ordinary switch to a dry circuit switch. And switches designed for dry circuit use normally have a tiny form factor that is not suitable for use on a lathe.

Although not an ideal solution, there is one way to skin this cat that is not too difficult. It requires the use of a dry circuit relay with bifurcated contacts that would provide the logic switching input to the controller while the existing mushroom switch would act like a normal current-carrying switch to drive the relay. A relay with an operating voltage of 24 VAC would work well which means that you would also need a 24 VAC transformer to power the relay. A typical HVAC control transformer would work well here. Another advantage of the relay is that you can get one with several sets of contacts and then wire them in parallel for redundancy against a failure in a single set of contacts. The plug-in type relay with an octal base would be a good candidate for this type of application.
 
I haven't measured it on the Powermatic but on the VFD that I've installed the switching voltage is only 24 volts. This should make a difference in the arcing problem I would think. I still go with the dust because I simply blew out my remote and it worked fine. Very interesting discussion.
 
The softening point for both silver and copper are both slightly less than 0.1 volts and the melting point is around 5 volts. Just to be clear, those are the voltages when current is flowing ... in other words, the contacts are closed. This means that high voltage is not necessary to cause contact erosion. The type of contact is more important that what the applied voltage happens to be.

I have not looked at the Delta controller manual (that is the brand that is used on the Powermatic lathe ... it is a Korean company and has no relationship to any of the other Delta brands such as Delta Machinery, Delta Airlines, or Delta Faucet), but in general, these controllers use 15 volts DC for their logic inputs and that is what my Baldor controllers use and also an LG (another Korean brand) controller that I have uses. It is possible that the Delta controller has relays built in so that the input can be electrically isolated. Since I have a manual, I ought to take a peek to see what it has.

Bill
 
Stock switch includes:

Yellow plastic box with magnet, paddle switch and long pig tail for wiring to headstock.

Link HERE
 
Bill,

I have a 3520A that is about 4 years old and it has a Delta controller. If you need a model number I can get it.

Clem

boehme said:
I have not looked at the Delta controller manual (that is the brand that is used on the Powermatic lathe ... it is a Korean company and has no relationship to any of the other Delta brands such as Delta Machinery, Delta Airlines, or Delta Faucet), but in general, these controllers use 15 volts DC for their logic inputs and that is what my Baldor controllers use and also an LG (another Korean brand) controller that I have uses. It is possible that the Delta controller has relays built in so that the input can be electrically isolated. Since I have a manual, I ought to take a peek to see what it has.

Bill
Click to expand...
 
I have ordered the PM remote switch. I still don't know how to wire it in, although I do understand the problem of using a switch to effectively unplug the lathe. Will the PM switch come with wiring instructions?

Bill
 
Bill the switch does come with instructions. The only problem I had was the 2 cords won't fit in the hole with the rubber bushing in place.
 
3520 Remote Switch

Bill,
My switch came with instructions. Only problem was that the colors of the wires in the instructions didn't match what was in the controller. Be prepared to call Technical Service, and they can fill you in on which wires go where.
Kurt:)
 
wiring

can you just hook up to a dryer outlet for the mustard for general power supply
 
3520b

Mikie,
If you're talking about the standard dryer plug and outlet, yes, it will work. Kinda overkill, though. If you go to the borg, look for a 220V, 20Amp plug and socket. They might even be a little less expensive, but I'm not positive about that.
Kurt
 
Mikie said:
can you just hook up to a dryer outlet for the mustard for general power supply
Click to expand...

You can, but strictly speaking, dryers are the only appliances permitted by the NEC to use that style outlet. Also, it is a violation of electrical code to modify your house wiring to add an additional outlet (regardless of the style of receptacle) to the same branch circuit that the dryer is on.
 
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