Building a Pickup Winder and Trying Not to Electrocute Myself

[whitebison66]

I'm building a pickup winder from a fan motor and I have a few questions I am hoping some of the good folks here can answer.

I've asked in another forum but received no answer, and I can't really proceed until I find this stuff out.

I've mounted the fan motor on a piece of wood, drilling a hole for the post (that I couldn't remove). I've immobilized the motor with L brackets that are only screwed into the  wood. They make contact with the motor; is that okay?

I've bought a dimmer switch for a speed control that, according to my readings on the web, will work if I put it in line AFTER the Off/Lo/Med/Hi switches  (i.e. between the switches and the wall plug). According to the stickers, the ratings seem okay, but again I want to ask people who know more than me (i.e. just about everyone).

I'm thinking to use a mechanical switch as a counter and have chosen (but not yet bought) the switch and counter. I am assuming (!) that I can use the retention pin on the fan shaft to hit the switch (see attached photos).

So I am asking if anyone can tell me if I am at least not making any major or life-threatening mistakes so far.

 

[whitebison66]

Here's the motor with the brackets.

 

[Dan025]

hmm... not sure i dont know enough about that motor. is that a brushed motor? or an induction motor? it apears to have multiple taps for speed control. it looks to me to be an induction motor offering presets that divide the rpms into whole number divisions of the max rpm.

if it is an induction motor it may have a strong tendency to meet the rated rpm for each setting, reducing voltage or pulse width with a rheostat or variac will reduce torque and in effect speed under load but without a very constant load (like what a fan sees) you might find speed control to be a bit hard to dial in. this is because the ac power rotates the magnetic field during motor startup and then just alternates (assuming single phase) if the motor shaft is going slower than the alternating field then the polarization of the core must "slip" eddy currents in the core resist this from happening too fast and when the slip is minimal the motor is syncronous with the field and current is minimal, when the motor is "slipping" the current goes up fast as the motor tries to keep up to the field and thus the motor draws more power, but a variac might give a reasonable amount of speed control, i'd guess that the "off" periods would give time for the field to collapse and allow the polarization to slip more readily, i really never tested that kind of control on an ac motor so im going off theory here. the best way to control an induction motor is with a variable frequency drive but then you are talking more money.

if the motor is brushed like the motors in a power drill (or a sewing machine... hint hint..) or other high speed ac motor then the voltage or pulse width will have a better relationship to the speed like it does on a dc motor. if your setup proves problematic sewing machine motors are quite powerful and sewing machines have speed controls that are designed to work with the motors so that should be a good alternative.

a vfd on an induction motor would give the ultimate in consistant linear speed control that is simple to wire and doesnt require an external sensor but the cost is high.

that said.. as far as i can tell you are not in any more risk of electrocution than wiring up some circuits in your house.

 

[whitebison66]

Thank you for the reply!

I wanted to use a sewing machine motor, believe me! Unfortunately, sewing is not a very big hobby here in Hong Kong, so the ability to buy anything but a brand new machine is not really there.

I'm glad also that I at least won't fry myself. That's probably the biggest thing.

 

[whitebison66]

Well, that rheostat doesn't work very well with the fan motor. It goes from stationary to too fast almost immediately and therefore is useless.

I have a line (hopefully) on a sewing machine motor, so keep your fingers crossed for me.

 

[Dan025]

if you got about $50 us and money for shipping to china (what ever that costs)  you might be able to get a vfd for that fan motor, it turns out only the more sophisticated ones cost $500.

http://dealerselectric.com/item.asp?cID=28&PID=996

the inexpensive ones are variable torque which means they are simple in design and are intended for fan or low output pump controls, they lose torque as speed drops (similar to what will happen with the sewing machine motor). constant torque vfd's are more like $100+. the $500+ examples have special algorithms for speed control and are very smooth and have full torque at rediculously low speeds as well as the ability to drive the motor harder as it senses load by making changes to the amplitude and/or phase and frequency of the sine waves all through detected changes in the motor speed from the windings in the motor.. pretty cool stuff actually... but i think what you need is a very low cost constant torque type and might even get away with the variable torque type.

the sewing machine motor is probably better for a first time build though and is probably more like what they used in the 50's. you will just have to hone your skills with that foot controller. it'll be much more controlable than a rheostat on a fan motor but the torque losses from the speed control will mean you still need to strike a balance with your tension (are you hand winding these?) and the pedal position. i've never tried but could imagine it's an aquired skill. in contrast a constant torque vfd will give fine speed control and load will have almost no effect on speed. to clarify the vfd is not for sewing machine motors, only induction motors.

 

[Patrick from Davis]

Or a variac would work as well.  Dimmers are not the most linear running things.  According to eBay, there are a lot of places that make/sell variacs from china.
Patrick

 

[Dan025]

a variac might not work that well, but probably better than a rheostat. refer to my first post. induction type ac motors are weird.. the only way to control the speed without huge losses, a big lack of torque and non linear control is with a vfd. you actually need to change the hz of the power because the core in the motor gets polarized and the rpm syncs to the hz.

sewing machine motores on the other hand have brushes and act more like dc motors.

 

[whitebison66]

Okay, I got hold of a sewing machine motor, and the dimmer does a MUCH better job of controlling it.

So my next hurdle is figuring out how to wire up the micro switch and counter.

There are two unmarked wires on the counter, and the three terminals on the switch are COM (common), NO (normally open) and NC (normally closed). I assume there's got to be some power to one or both components, but I don't know how to wire it.

 

[Dan025]

hmmm... just two wires on the counter. well the counter is rated for 220v my best guess is that any time it gets 220v across the two wires it counts 1 and stops till the power is removed and reaplied. well normally you connect power to the common on the switch so hook a hot leg to that. really it doesn't even matter if you use the normally open or normally closed side of the switch since the switch will toggle back and forth for each revolution but i would say using normally open would be more conventional so connect normally open to one of the wires on the counter and the other wire of the counter to the other leg of the power cord. it's ac so polarity doesn't affect functionality, but it affects safety in the case of 110 where you have a neutral which isn't generally dangerous, the neutral would normally get connected to the powered device and the hot would go through the switch so you could see how that would be safer being that turning the switch off renders most of the circuit safe. normally with 220 you don't have a neutral so there is really no distinction between the 2 legs.

now is that sewing machine motor 220v? or 110v? i don't know how power works in china.. but in the states 220v is 2 110v hot legs phased 180deg apart, and 110 is a single hot leg and a neutral. how many prongs are on the power connectors? and do you have a multimeter?

 

[whitebison66]

The electricity in HK is the British 3-prong type. The motor is 220v AC (see photo).

If I understand, I need to run a wire from the hot/live side to the COM lug on the microswitch, one counter wire to NO, and NC to... live?

I do have a multimeter, though I'm none too good with it.

 

[Cagey]

He's saying forget about NC vs. NO, although NO is probably a better way to go. Whichever way you go, you won't use the other terminal. It's a series circuit where you want a switch to open and close to the load (the counter) once each revolution. Whether it starts open or closed matters little.

I was going to suggest hiring an illegal alien to count the revolutions and forget all that wiring gimcrackery, but I forgot you don't live here <grin>

 

[Dan025]

The electricity in HK is the British 3-prong type. The motor is 220v AC (see photo).

If I understand, I need to run a wire from the hot/live side to the COM lug on the microswitch, one counter wire to NO, and NC to... live?

I do have a multimeter, though I'm none too good with it.

only 2 connectors on the switch are needed. as long as you are using the common and just one other connector (NO) you are ok.

one wire from the cord to the common, one wire from the cord to the counter, one wire from the counter to the NO.

 

[whitebison66]

That combination didn't work  :dontknow:

I'm trying to read up on these things, but there's not a lot to be found (that I can understand).

 

[Cagey]

It's a very simple circuit. The switch is just in series with the counter.

Every time the switch closes, the counter clicks over a count.

The only reason I can see that not working is if that counter is not a 220v part, which I'd put a high probability on. Devices like that are often low-voltage parts, like 24vac or some low DC level. So, first time the internal solenoid saw 220vac, it'd open up like a fuse, probably so fast it wouldn't even burn.

It's also possible the switch isn't mounted in such a way that it reliably opens and closes.

 

[whitebison66]

Thanks Cagey, I will try this.

To make sure:

COM and NC are jumped together?

L1 and L2 are both from the live/hot wire (i.e. no ground wire in this)?

Wish me luck!!!

 

[Cagey]

No, there aren't any jumpers anywhere. That's an internal representation of the switch. Should've put some dotted lines around it or something. Here's a better representation at the bottom...

L1/L2 are Line 1 and Line 2, which are the two sides of whatever power system you've got going there. Hot & neutral, hot & common, hot and ground, hot and return, just plain old "supply lines", the list is long.

 

[whitebison66]

Okay, thanks!!!

 

[whitebison66]

Thank you Cagey; it works!

 

[Cagey]

Cool! Glad that worked out for you.