Gunsmith needs to wire a DPDT switch!

[littlefraggle]

Hello from Kent, I have forgotten the tiny amount I learned about electrics and I need to wire a DPDT switch to control a 230V 50Hz synchronous motor and just haven't a clue and don't fancy killing myself. Very much DIY electrics but I'd appreciate any help (I have project box, gland, soldering iron, terminal strips, a switch some flex and a plug 13A).

Happy to swap advice if anyone has a wonky hun they need sorting out!

Cheers

 

[HandySparks]

What do you want this switch to do?

 

[Marvo]

Why are you using a double pole, double throw switch?

 

[littlefraggle]

I need the switch to control a motor that slowly draws a piece of work out of a tube of varnish and then slowly lowers it back into the varnish. The process takes 3 hours or so and I don't want to stand there for six hours winding it by hand ideally.

 

[HandySparks]

So the switch is intended to reverse the motor?

 

[Deleted member 72666]

Best let an experienced spark do this for you. But hey, don't shoot the messenger.....!

 

[littlefraggle]

Yes it's to reverse the motor. There are 6 terminals, if there were 26 - I'd be calling a sparks but it just can't be that hard...

 

[Marvo]

Can you take a picture of the motor terminal box and attach it in the thread? How this would wire would very much depend on the arrangement in the motor terminal box, if there's a diagram inside the box lid please include that as well and the make and model number of the motor.

Would it be better to use a timer to run the motor one direction then automatically change direction? Does the motor run constantly throughout the dipping process and does it have limit switches built in?

 

[littlefraggle]

The motor just has two wires coming out of it. It can run either way. I just need to connect it to the switch please. A timer won't work as once the item is wound to the top, ho do I then lower it. This is a tiny 2" wide synchronous motor not some huge 3 phase thing.

 

[Marvo]

Ahh, I was picturing something more industrial but it sounds like one of those very small motors they use in a microwave to drive the glass turntable plate around.

Is there a capacitor somewhere on or external to the motor? Are you sure it's only got 2 wires, if so how does it reverse? Is it anything like this one? It would still help if I could get a make and model number.

 

[littlefraggle]

It's a bit like that yes, it's a rod drying motor off the bay. Only says 230v and 50Hz on it, two thin blue wires. I planned to use the switch to reverse the motor polarity as others do. I was planning to wire the motor into a connection block and then into the switch in one of those plastic boxes we used at school!

 

[Marvo]

As far as I know if the motor only has two wires coming out of it then it can't be reversible.

I'm not an expert on these little motors but I don't see how you're going to make it reversible without at least 3 wires or maybe 4 wires plus you'll need a capacitor. With an AC motor just reversing the supply wires won't change the running direction.

 

[littlefraggle]

OK thanks for the advice. I'll give it a go and post how I get on.

 

[littlefraggle]

Am I missing a trick here?

 

[littlefraggle]

Motor has two wires, power supply has two wires. Motor rated 230v 50 Hz input supply is 230v. Wire as per diagram or am I about to fry myself?

 

[littlefraggle]

Here is the motor

 

[HandySparks]

Your reversing diagram in post 14 only works for DC motors.

What Marvo was alluding to in post 12 was that this doesn't work for 2-wire AC motors.

 

[littlefraggle]

OK thanks. I have a rod dryer here on my bench that has the exact same motor and a rocker switch, no PCB of any sort and is wired to a UK plug - if I turn it on the motor turns. If I turn it off and then on again, the motor reverses. Please explain that as I'm clearly a bit dense. No DPDT switch though.
Am I over complicating it?

 

[HandySparks]

OK thanks. I have a rod dryer here on my bench that has the exact same motor and a rocker switch, no PCB of any sort and is wired to a UK plug - if I turn it on the motor turns. If I turn it off and then on again, the motor reverses. Please explain that as I'm clearly a bit dense. No DPDT switch though.
Am I over complicating it?

Ah! Some synchronous motors will set off in the opposite direction each time they're started. Others use some sort of internal mechanical device to set their direction of rotation. Once it's going, the motor will keep going in the same direction. You can test this out with your new motor by just connecting it up and seeing which way it turns. Switch off, then on and see if it changes. Then try connecting up with the supply reversed and see if it makes any difference.

 

[littlefraggle]

I thought that using a DPDT switch (£2) would make it a dead cert. I'm just trying to wire the clucking thing up so I don't get fried and the motor reverses!

 

[PEG]

Hi dude,will this rig use limit switches to reverse direction?

The reason i ask,is i have made a rig up,to do a similar task,and because of its' repetitive nature,i simplified the need for switching. You should be able to have the motor running continuously,and have the "stroke" cycle,achieved using small pulleys,cranks or a cam.
This,and don't laugh,is made easy,by using childrens mechanical construction kits,such as meccano.
There are other self-build childrens kits,which are strong enough for the size of motor you have shown.

The benefit of this,apart from simplicity,is it is easy to change stroke length,etc,should you change from action parts,to stocks or tie-dying tee-shirts!

Also,if it is being left unattended for long periods,and you are unsure of the safe-guards on your 230 volt motor,there are lots of DC motors,coupled with a suitable PSU,which could avoid the worry.

If you can stop a Baikal double discharging,the above will be doddle! Good luck :icon12:

 

[Marvo]

Ah! Some synchronous motors will set off in the opposite direction each time they're started. Others use some sort of internal mechanical device to set their direction of rotation.

You obviously have more experience than me with this type of motor. What you say makes sense, it's only got 2 wires and no cap so it must have some built in function that auto reverses it each time it starts. If this is the case then the DPDT switching arrangement is unnecessary, just a standard single pole on/off switch or just using the DPDT switch in that configuration would work fine.

The wiring diagram you've shown fraggle won't cause damage but it's probably not going to achieve anything more than wiring it as normal on/off. Maybe just as an experiment wire the motor using a choc block to a cable with a plug on it and try plugging it in an out a few times to see if it consistently auto reverses each time power is applied. It would be much safer if you connect the earth wire to the body of the motor as well before experimenting.