Clarke 150TE Wire feed motor upgrade runs on too long

[tigdlo]

Hello,

I have fitted a new wirefeed motor and when the trigger is released it runs on and wastes about 2" of wire each time.

The motor label says 24v 4A but is chinese rated and is infact 1A at 30v while under more load than is experienced while welding.

Is the welder possibly faulty? Should it brake the motor? If not does anyone know of a motor brake modification?

There is a large resistor between the PCB and motor that isn't shown on the wioring diagram in the manual but it does look like it should be there.




Thank you for any help

 

[roofman]

You could try screwing in the spring on the wire reel to bring in more resistance...sometimes the weight or the reel if slack can keep moving forward by inertia

 

[tigdlo]

You could try screwing in the spring on the wire reel to bring in more resistance...sometimes the weight or the reel if slack can keep moving forward by inertia

Thanks, hadn't thought of that, I'll give it a go.

 

[eddie49]

The small MIG welders don't generally have any braking circuitry in their speed control circuits. Maybe they rely on friction in the plastic gearbox to stop run-on.
The usual way to implement braking is to short-circuit the motor, using a relay or triggering a power transistor or thyristor across it.
This is often done as a complete upgrade, where not only the wirefeed motor assembly but also the speed controller and the supply for it are replaced.

 

[caprinut]

Don't they use stepper motor in those, if not a stepper motor then it won't show discreet steps for lengths on releasing the trigger.

Bert

 

[tigdlo]

Don't they use stepper motor in those, if not a stepper motor then it won't show discreet steps for lengths on releasing the trigger.

Bert

Hello, deffinately a standard DC brushed motor, both the original and replacement, its the intertia that keeps it going once the trigger is released. The original motor was small with loads of gears so less inertia in the motor and more friction in the gears. Now it has a larger motor so more inertia and fewer gears so less friction.

The reel tension hasn't made an improvement, I think I've made life difficult for my self by choosing the worm and wheel type motor, maybe the smaller motor with gearbox type would have been better.

 

[eddie49]

I would have thought that a worm-and-wheel gearbox would have been ideal for this application, since it does not allow the drive roller to be forced to rotate by inertia of the wire spool. So with the 2" run-on that you are seeing, this must be due to inertia of the motor armature? That seems to be excessive, perhaps the power source, which is tapped-off from the main welding transformer output, or the type of speed control circuit, is to blame - i.e. power to the motor is not being cut off cleanly on release of the trigger.
Is the power semiconductor on the heatsink a transistor or a thyristor?

 

[tigdlo]

this must be due to inertia of the motor armature?

That's what I thought,

If it's electrical I can test this by pulling the spade terminals apart and seeing how far it runs on as it will disconnect it from the power supply.

 

[Gareth J]

You could try a relay to short the motor terminals as a relatively cheap/easy thing to do.

I've never actually tried this, presume it works but don't know at what cost to brushes/wear;
https://electronics.stackexchange.com/questions/16654/braking-a-dc-brushed-motor

Something like this

 

[eddie49]

Depending on the speed setting, the voltage coming out from the wirefeed speed controller could be anywhere from 8 to 26 volts, and/or it may be pulsed, so selecting a suitable voltage for reliable operation of the relay coil will be difficult.
Additionally, if it is suspected that the voltage from the speed controller may stay up too long and let the motor continue spinning, then that voltage will also keep the relay closed if the relay coil is wired to the same source.
I would suggest wiring the new relay in parallel with the existing one that switches AC power to the main transformer. I think it is the large black plastic rectangle on the PCB, but I don't know what the coil voltage is.
Alternatively, a relay with a mains-voltage operating coil could be put across the switched transformer primary.

 

[Monkeypeas]

Alternatively, a relay with a mains-voltage operating coil could be put across the switched transformer primary.

This right? even drew a pretty picture and everything, its probably what i'd do, take the 230v switched the same place you'd take it to fit a gas solenoid, a million people have done that, there will be threads on here giving you the pins to take it from.

 

[Gareth J]

Depending on the speed setting, the voltage coming out from the wirefeed speed controller could be anywhere from 8 to 26 volts, and/or it may be pulsed, so selecting a suitable voltage for reliable operation of the relay coil will be difficult.
Additionally, if it is suspected that the voltage from the speed controller may stay up too long and let the motor continue spinning, then that voltage will also keep the relay closed if the relay coil is wired to the same source.
I would suggest wiring the new relay in parallel with the existing one that switches AC power to the main transformer. I think it is the large black plastic rectangle on the PCB, but I don't know what the coil voltage is.
Alternatively, a relay with a mains-voltage operating coil could be put across the switched transformer primary.

Good points! Much better idea

 

[tigdlo]

Thank you all, only took 9 months but I didn't need to mig weld until now, I used a 240v coil relay as suggested by @Monkeypeas, haven't tested it welding yet but see the videos for the difference. I did start and stop the motor by manually pulling off one of the wires to rule out the pcb not switching off as it should but it really was just the inertia of the motor. I'll tidy up the wiring and test it tomorrow.