Remote Control DC on the Cheap

[NCTurner]

Picked up a pack of these at Lowes for $19.99. 3 110v outlets with 1 remote control.

http://www.buy.com/retail/product.asp?sku=209681020&listingid=33907829

 

[PChristy]

Cool deal Gary :icon_thum

 

[merrill77]

I don't suppose safety is too much of a concern with a DC, but you might want to consider that these are not rated for motors and have a 10a limit - which will be exceeded on startup for many DCs. This means there is a small chance that the startup current could cause arcing of the contacts and "weld" them together. After which it would not be able to turn back off.

 

[NCTurner]

My Delta AP300 is rated as follows so shouldn't be an issue:

Motor: 3450 RPM, 3/4 HP, 120/240V (wired 120V), 9/4.5 amp, 60 hz, 1 Phase

 

[junquecol]

I don't suppose safety is too much of a concern with a DC, but you might want to consider that these are not rated for motors and have a 10a limit - which will be exceeded on startup for many DCs. This means there is a small chance that the startup current could cause arcing of the contacts and "weld" them together. After which it would not be able to turn back off.

Put a 110 volt (coil) relay on it, or rob both low voltage transformer and relay from an old furnace. Lowes also has two others on sale, one for about $8 and another for about $14. Sunday, Apex Lowes couldn't find the $8 ones, so wife got the $14 for $8. The $14 one will handle 15 amps, and has 3 outlets. I have one in my shop to control AC unit. On one frequency, the lights on the side of the house come on, and on the other, lights in tree, in front yard come on.

 

[McRabbet]

Gary,

I know you think you got a good deal, but I'll be willing to bet they won't last very long -- certainly not as long as my Shop Fox Remote Dust Collector Switch that I bought about 10 years ago for under $40 (now cost about $45 at Klingspor). It handles 15 Amps and is designed for motor loads. I'd suggest you use your for Christmas Tree lights or room lights, not a nearly 10 amp motor. JMTCW YMMV

 

[Gotcha6]

Chris is right about the starting load. With the rotational mass of the impeller, the motor could go as high as 250% of the full load amperage for less than a second - enough to arc and fuse the contacts in this controller. I believe they are only designed for lamps & radios & such - like you'd have in your bachelor pad to set the mood.:gar-Bi

 

[CrealBilly]

My remote control DC on the cheap consists of me telling my son to go sweep out my shop. :rotflm:

 

[junquecol]

My remote control DC on the cheap consists of me telling my son to go sweep out my shop. :rotflm:

Cheap- no way. As for as expensive, a child is only second to a lady who says she is free for the evening.$$$$$$$$$$$$$$$$$$$$$$$$$$

 

[Alan in Little Washington]

Dennis is absolutely right. Wire that remote to a contactor relay. It would be more useful in a shop if it had one outlet and 3 remotes, in case you lose or misplace the remote.

 

[merrill77]

They have most likely listed the current draw when the motor is running (possibly under typical load). The start-up current draw will be much higher. I've gone down this road myself - using a particular type of light switch on my TS - and the switch failed (twice) after only a few months. Luckily for me, it never failed in the "ON" position. It's a bit embarrassing, really, as I'm an electrical engineer and I should have known better.

 

[Alan in Little Washington]

Let me add some details about what happens when a switch is used to control equipment for which it is not rated. Most of these small, inexpensive remote switches are designed to control resistive loads (lights) not inductive loads (motors) and have mechanical relays inside. You can verify if it has a relay, by operating the remote while listening carefully to the receiver unit. If you hear a click or other mechanical sound, it has a relay. There are electronic switches out there, but they are rare, especially at those prices.

The contacts in a switch (or relay) that is used to control equipment, especially a motor, that draws current near, or in excess of, the switch's amperage rating will work ok initially. However, each time the switch is activated there will be some internal arcing as the contacts close AND open. Over time this causes erosion, pitting, and corrosion build-up on the contact mating surfaces and eventually prevents proper contact.

The higher the switched current, the hotter the arc and the greater the erosion. Contact erosion also increases with longer arc duration because of high switched voltages. Also, contacts that switch inductive currents (motors) erode quicker than those with resistive loads. Accelerated erosion is caused by contact arcing that results when the deenergized inductor returns its stored energy to the circuit (when you turn the motor off).

Poor contact can cause the switch to heat up rapidly, smoke, melt and/or fuse the contacts, and even cause a fire before the contacts fail completely or a breaker trips.

Anyone still awake out there? :wsmile:Sorry this was a bit long. I just thought you all needed to know.

A couple of us have recommended that if you want to use one of these remotes you use it in conjunction with a relay contactor. An astute reader will realize that you will be using the remote to control power to the contactor's coil- which is also partially an INDUCTIVE LOAD. The difference is the inductive component and the current demands of the contactor coil are much less.

The above information is available on the internet.

 

[NCTurner]

Thank you all for your responses. Given the knowledge base on this forum, I have decided to go to a remote rated for my DC. Thanks for the feedback. This would be a prime example of JUST ONE of the many reasons I post on this forum.

Thank you all. Keep looking out for a brother.

 

[CarvedTones]

Hmmm...
Now you have me worried about this uhm, friend of mine who has a little joiner powered by a 1/2 HP washing machine motor and uses a light switch to power it off an on. He might have a profile sander with exactly the same type motor and wiring. Is this likely to have the possible corrosion and fire damage mentioned?

 

[Mt. Gomer]

Hmmm...
Now you have me worried about this uhm, friend of mine who has a little joiner powered by a 1/2 HP washing machine motor and uses a light switch to power it off an on. He might have a profile sander with exactly the same type motor and wiring. Is this likely to have the possible corrosion and fire damage mentioned?

I think the key bit for , uh, "your friend" is the part below....

The contacts in a switch (or relay) that is used to control equipment, especially a motor, that draws current near, or in excess of, the switch's amperage rating will work ok initially. However, each time the switch is activated there will be some internal arcing as the contacts close AND open. Over time this causes erosion, pitting, and corrosion build-up on the contact mating surfaces and eventually prevents proper contact.

Most standard lightswitches are rated 15A, the heavier duty ones 20A. Which does "your friend" use and what would you estimate the startup draw of "his" moter to be?

 

[Bas]

Hmmm...
Now you have me worried about this uhm, friend of mine who has a little joiner powered by a 1/2 HP washing machine motor and uses a light switch to power it off an on. He might have a profile sander with exactly the same type motor and wiring. Is this likely to have the possible corrosion and fire damage mentioned?

1/2 HP is only about 350W, which is about 6A. That's a far cry from the 15A rating for the typical light switch, even when taking into account the fact that it's switching an induction motor (as Alan explained). Is it recommended? Of course not. Is it dangerous? I wouldn't lose any sleep over it.

Granted, I'm not an electrican or engineer, and didn't even sleep in a Holiday Inn last night, but I've seen lots of posts showing people use a light switches to power table saws & router tables. Of course, it wouldn't hurt to examine the switch for any damage or signs of trouble. But that applies to all outlets and switches in the shop.

 

[merrill77]

Is it recommended? Of course not. Is it dangerous? I wouldn't lose any sleep over it.

If the contacts are fused "on" when you _really_ need to turn the tablesaw off, then yes. But the odds are pretty good that it will never present a danger. By the same reasoning, it is unlikely that any of our houses will burn down...but we still have insurance.

Of course, it wouldn't hurt to examine the switch for any damage or signs of trouble.

AFAIK, that cannot be done. Most of those switches cannot be dis-assembled non-destructively.

In my case, the switches simply failed to turn on...at a regularly frequent interval. The time spent changing $1.99 switches quickly exceeded the $25 cost for the correct switch (I think I picked mine up online).

1/2 HP is only about 350W, which is about 6A. That's a far cry from the 15A rating for the typical light switch, even when taking into account the fact that it's switching an induction motor (as Alan explained).

Being able to handle N amps is a totally different aspect from being able to handle inductive loads. It doesn't matter if the switch can handle 100A resistive load. A significant part of the design difference is the distance over which the contacts separate and the speed at which they separate during on-off transitions. A switch for resistive load need only separate the contact by a millimeter because 120V can't arc across that (1mm is just an example, I'd have to look up the actual numbers). A switch for inductive load must separate the contacts by much more than that. As I understand it (and it's been a long time since EE school) this is because when you cut power to an induction motor it instantly turns into a generator. With an open circuit and nowhere for the energy to go, the voltage spike can be tremendous - thus the arcing across the contacts. In addition, contacts on an induction-rated switch are spring loaded. They move very quickly between full-on and full-off, regardless of what the operator does with the switch. A common lightswitch, by comparison, can be slowly moved from full-on to almost-on and left that way. Try this with a light switch and you can sometimes hear the arcing. The time from contacts-closed to contacts-fully-open is important in reducing arcing.

Just my final 2c
:>

 

[CarvedTones]

I will have to see what the ratings are. "My friend" might have picked up the cheapest light switch on the shelf at Lowes. I keep telling that guy not to be so cheap, but does he listen? :rolf:

 

[SteveHall]

"My friend" might have picked up the cheapest light switch on the shelf at Lowes. I keep telling that guy not to be so cheap, but does he listen? :rolf:

Heh! Andy, don't worry, you're not alone. I have "a friend" that does the exact same thing!

 

[Alan in Little Washington]

If you want to use a wall switch, find an old "silent" one. The contacts were enclosed in a vial that had a glob of mercury. The switch action tilted the vial so the mercury either bridged the contacts or pooled at the opposite end of the vial. I wish they were still available. The sparking sound made by modern wall switches in my house really bothers me.

If you don't want to spend $ on a new contactor, do what someone here suggested- get a used one from an HVAC shop. They might let you have one for free- direct you to their junk pile and tell you to knock yourself out, so take your tools.

If using the remote, you will want a contactor with 115V coil rather than a low voltage (24V) coil. One with a 24V coil will work, but you'll need a transformer- the HVAC equipment will have one of those too.