Changing a motor's direction each time power is supplied

[StewartVivonne]

I hope I can get some help here, I'm a heating engineer with not much electronics savvy, and I need to modify the motors on one of our products.

It's a motor that turns, controlled by a timer. so it turns for 10 seconds every hour. because it always turns in the same direction it sometimes gets itself in knots (it is used for vacuuming up wood pellets in a silo)

So I'd like a relay, a DPDT relay for example that will change the ploarity of the motor each time it is supplied.

It is a 220V motor with 2 coils, one working coil and one starting coil (wired to the condensor)

Any help will be greatly appreciated

Thanks

Stew

 

[Joe G]

welcome aboard. How about a flip-flop for starters....

 

[StewartVivonne]

ah you're getting too technical already!!

 

[dougy83]

Is this 220V DC or AC?

 

[StewartVivonne]

220V AC

I've been reading about DPDT relays and the change of direction seems straightforward, my big problem is how to automate the switch. The motor is supplied for 10 secpnds every hour, how does it remember that the last time it turned clockwise and now it has to be anti-clock and the next time clockwise etc?

 

[alec_t]

how does it remember that the last time it turned clockwise and now it has to be anti-clock

That's what the suggested flip-flop is for. It stays in a given state when not triggered, then reverses its state when triggered.

What is the power rating (or running current) of your motor?

 

[StewartVivonne]

30watt 220v single phase. I've seen it turn in reverse when I change the wires over

 

[alec_t]

I'm a heating engineer with not much electronics savvy

The project looks doable, using a DPDT relay plus some electronics. I'm sure you appreciate the dangers of working with 220V systems. Would you be able to construct and install, safely, an electronic circuit if we could design one for you?

 

[crutschow]

Is this for production or a one-of-a-kind requirement?

I assume there's no power to the motor when it is off. (?)

You could likely use an alternate action (bistable) relay such as this. It changes state every time the power is applied to the coil. One concern is if the relay coil can tolerate continuous actuation (it's not clear from the data sheet). If not then a circuit to apply momentary power to the relay would be needed.

 

[StewartVivonne]

Safety is paramount, this thing sits in a silo full of combustable wood pellets. That said, the manufacturers already have the motor, condo, wiring etc in place. The 220 volts plugs in via a 3 prong kettle cord... and yet it conforms to european standards so a relay and circuit in a box inside the existing box won't be escalating any risks. if necessary the additional circuitry can be sealed to make it airtight and spark proof...

The control box that handles the timings etc is at the boiler. It cuts off all power when the motor is idle

 

[panic mode]

why not use smart relay? you can program it to do anything you like....

 

[KeepItSimpleStupid]

A "smart relay" is probably a good choice for this. Another relay that MIGHT be useful is called an IMPULSE relay. Each pulse changes the state.

 

[StewartVivonne]

.

 

[KeepItSimpleStupid]

I just want to point you to here: https://us.idec.com/Catalog/Product...DEC_SmartRelay&FamilyName=Programmable_Relays Idec
s smart relays. You can play with the graphical programming for free. It does require a development kit of sorts

Moving for every 10 seconds and reversing doesn't sound too good either. Won't a vaccum turning backwards, blow?

Can the motor being used actually be reversed?

Other algorithms like reverse the direction every 3 minutes of operation (X activations). You also have wear on the reversing relay as well.

Something like:

When > x activations or run time.
Is motor running? Wait for stop. Wait x sec after stop.
Lockout motor run.
Change direction.
Remove lockout from motor run.
Set activations to zero.

 

[panic mode]

try Zelio software, it is free. it supports ladder logic and function block diagram. plus it has simulator so you can write and test code before actually purchasing smart relay... then just send your program and be done. if you need to change it any time - no problem, like all smart relays it is reprogamable

 

[panic mode]

or Click plc from AutomationDirect (free software and low cost hardware)

 

[chemelec]

The real question Might Be: Can that motor actually be set in a Reverse Rotation?

Not all types of motors can be operated in Reverse.

 

[panic mode]

he mentioned earlier that it can, the only thing needed was something to control it, or at least this is what i understood.

 

[StewartVivonne]

There is already a control box that handles timings, all I need is at the motor end is to switch polarity

 

[StewartVivonne]

i was thinking of an impulse or keep relay followed by a DPDT relay