Clausing Drill Press (new to me)

[rwm]

I just got this sewing machine motor in the mail today:

In spite of its small size it is rated at 1HP and goes up to 4000 RPM. I plan to replace the drill press motor with this and have the added advantage of full speed control. I hope the torque will be adequate. I plan to use the pulleys to get about a 2:1 speed reduction.

This motor comes with a max speed setting on the control box as well as a variable speed foot pedal. Here is the pedal control:

As you can see, it uses a magnet that sweeps over a Hall effect sensor. I am not versed in the operation of these sensors. I would like to convert this to a simple ON/OFF switch that starts the motor at maximum speed. Can anyone help me bypass the Hall sensor to achieve this? There are 3 wires coming from the circuit board. I assume red is V+, black is Ground and Yellow is Signal? Can I simply connect yellow to V+ and get a full speed input?
Any other comments welcome.
Robert

 

[hman]

I'd suppose that the easiest way to find an answer would be to hang a voltmeter between one of the power leads and the output lead, turn the motor on, and set the speed control to max. If yellow goes to the same (or nearly the same) voltage as red, you can be assured it's safe to connect the two directly. The circuit board does not appear to have any other active components on it, so I doubt you'll have any trouble.

 

[rwm]

I'd suppose that the easiest way to find an answer would be to hang a voltmeter between one of the power leads and the output lead, turn the motor on, and set the speed control to max. If yellow goes to the same (or nearly the same) voltage as red, you can be assured it's safe to connect the two directly. The circuit board does not appear to have any other active components on it, so I doubt you'll have any trouble.

Well it's interesting....There is 5v across the red and black leads. The yellow goes to +5 when on full speed. However, I clipped of the leads from the circuit board and now I get a P4 error on the controller. P4 corresponds to Pedal Malfunction. Even with the error code, connecting the yellow to the red gets the motor to run at full speed. I tried putting a 1K resistor between the red and black but that does not stop the error code. I can use it this way, but any ideas?
Robert

 

[rwm]

I find it hard to make pulleys.

Got to get that 17 deg angle set and go back and forth and all that.
Robert

 

[hman]

Well it's interesting....There is 5v across the red and black leads. The yellow goes to +5 when on full speed. However, I clipped of the leads from the circuit board and now I get a P4 error on the controller. P4 corresponds to Pedal Malfunction. Even with the error code, connecting the yellow to the red gets the motor to run at full speed. I tried putting a 1K resistor between the red and black but that does not stop the error code. I can use it this way, but any ideas?
Robert

Maybe ... reconnect the Hall sensor, with a DC ammeter between +5 and the sensor. Calculate the correct dummy resistor load (R=E/I) from the current and 5 volts. Also verify that it doesn't vary too much when changing speed.

While you're at it, you could try measuring the voltage between +5 and the sense lead when "full on." If the voltage on that lead is slightly different from +5, the difference would be easier to measure that way than by trying to look for a difference between each of the leads and ground.

 

[rwm]

I hooked up a 20K pot with red and black at each end and the yellow wire on the wiper. As I suspected, the error goes away with the pot turned all the way down. The controller is looking to see that the signal is at 0V when you start up. This is a safety issue for sewing.
I would kind of like to use the pot as a speed control but here is the new issue. When you turn the dial the response is non linear. There is no motor response until the last 10 deg of rotation. Then you can control the speed but with very fine movements. I wonder if I have an audio taper pot? Would that cause this behavior or is the controller looking for something else?
Robert

 

[brino]

You likely just need a different pot value, one that better mimics the original magnetic sensor.

Is that last 10 degrees (where the motor works) with the wiper turned towards the red +5V lead, or with the wiper turned towards the black ground lead?

That'll tell us if you need a bigger or smaller pot value.

-brino

 

[rwm]

The functional range is the last 10 degrees towards the red. (Wiper towards +5V). Why would a different resistance value change this? Isn't the voltage divider the same in the same angular location? I guess that would in part depend on the impedance of the yellow input wire so you may be on to something. I have since tried a pot that I know to be linear. It was a little better but still had the same issue. I am wondering if the Hall output was non-linear and the controller was tuned for that?
Robert

 

[brino]

Oopps, I think you're right...........

My original thought was that the input was only expecting voltages say in the 4.5-5V range, so most of the pot was useless.
My mistake was thinking that changing the pot values would change that.......nope!
You're right that it's the ratio between the two virtual resistors made up by the pot.

But what could make a difference is putting a fixed external resistor (or two) along with the pot, to change the range it has.

Can you temporarily wire the foot switch back in and measure the voltage on the yellow wire with the pedal at zero, and the pedal fully down.
That would help define the voltage range required.

I am wondering if the Hall output was non-linear and the controller was tuned for that?

I bet that is true.
Is there any part markings on it?

-brino

 

[rwm]

You nailed it. I can put a resistor in line between the black and the pot -terminal. That would widen the functional range. I will play with values.
Robert