Member postings for Les Jones 1

A series wound motor is a bad choice for driving a lathe as it's speed varies a lot with load. They can be reversed (Both when supplied with AC or DC.) but you need to change the internal wiring of the motor to reverse the relationship of the current through the armature and the field winding. If you supply some details of the motor that is fitted that may be a better option than the Kenwood motor.

Les.

If it gives a change wheel setup for any thread you should be able to work out the leadscrew pitch. If you can't work it out post the information here ant there will be may members that can work out the leadscrew pitch.

Les.

7 BCD Scales
LSB Sent first.

Static state of clock line between frames Low
Time between start of frames 330 mS
Length of data frame 820 uS
Interrecord gap 329 mS
Time between stat of nibbles within frame 110 uS
Length of clock cycle about 12 uS
Time clock pulse is negative about 6 uS
Time clock pulse is positive about 6 uS
High level at start of frame about 55 uS
High level between nibbles about 60 uS
High level at end of frame about 60 uS

Clock in the data on the negative going edge.

Top nibble
Bit 0: sign. L = +, H = -
Bit 1: in inch-mode H means +0,0005 inch, unused in mm-mode.
Bit 2: unit: mm/inch. H= mm; L= inch
Bit 3: unknown.

28 bits in a frame of data

CPI 2540 (Metric)
-------------------------------------------------------------------------
iGaging (21 bit)

LSB sent first
The 21 bits are all used as a 21 bit binary number. (No bits used as flags.)

Static state of clock line between frames Low
Static state of data line between frames
Time between start of frames 7 mS
Length of data frame about 2.33 ms
Interrecord gap about 4.67 mS
Time between clock pulses about 111 us (Clock cycle time.)
Time clock pulse is negative about 89 uS
Time clock pulse is positive about 22 uS
High level at start of frame about uS

Clock in the data on the negative going edge.

CPI 2560

21 bits in a frame of data

-------------------------------------------------------------------------
I collected this information when I was writing code to read all the above types using an Atmel Attiny4314.

Les.

Hi Robin,
This information on scale protocols may help you.

-------------------------------------------------------------------------
Scale protocol information.

2 * 24 bit scales

Data is sent as two groups of 24 bits.
Each group is a 24 bit binary number. The first bit received is the least significant bit.

Bits
are transferred LSB first! Also, data is 2's complement. (ie inverted Data signal at 0 volts = 1 at +1.5 volts = 0)

Static state of clock signal between frames Low
Time between start of frames 330 mS Normal mode 25 mS fast mode
Length of data frame 860 uS
Length of clock cycle about 14 uS
Time clock pulse is negative about 7 uS
Time clock pulse is positive about 7 uS
Initial high at start of frame about 52 uS
High in the middle of frame about 110 uS
High at end of frame about 80 uS

Clock in the data on the negative going edge.

The first group is the absolute position. It has some arbitary value at power on.
The second group is the relative position. This will be zero after the zero button is pressed.
Its value will be the difference between the absolute value when the zero button was pressed and
and the current absolute value.

48 bits in a frame of data

CPI 20480

-------------------------------------------------------------------------

HF (Bin 6 scales)
LSB Sent first.

Static state of clock line between frames High
Time between start of frames 180 mS (I measured about 210 mS)
(I have seen 133 mS quoted elsewhare.)
Time of gap between nibbles about 700 uS
Length of data frame 13 mS
Interrecord gap 167 mS
Time between start of nibbles within frame 2.2 mS
Clock cycle time about 450 uS
Time clock pulse is negative about 320 us (Logic 1)
Time clock pulse is positive about 130 us (Logic 0)

Clock in the data on the positive going edge.

The data output is the number displayed on the LCD display.
Set scales to metric mode and this will corespond to 2540 CPI ( 0.01 mm) per count)

24 bits of data (6 bytes) Least significant comes out first. Bits 0 to 19 is the reading in binary (The same value as that displayed in decimal on the scale display. Bit 20 is the sign bit set for negative Bits 0 to 19 are always a positive number.
Bit 23 is set when in inch mode.

24 bits in a frame of data

CPI 2540 (Metric) (2000 in imperial mode.)

This is only half of it as it would not let me include it all in 1 post. The rest is in my next post.

Les.

Assuming that the black cable is the only other cable going to the motor as well as the blue cable to the capacitor then if the black cable is two conductors plus earth then the motor can't be reversed externally. If it is four conductors plus earth then it probably can be reversed externally. If you are prepared to take the motor apart then it may be possible to reverse it. This may involve digging into the end of the winding to get at the point where one end of the start winding is connected to one end of the run winding and to an external wire. the connection between these winding ends would have to be separated and brought out as two separate wires.

Les.

Hi Robin,
Thanks for the reply. I am now wondering if the connector on your scale is different to mine as the pin layout is different to a DIN connector.

Here are pictures of my plug.

Looking an the Farnell website I think I have identified the connector as a Binder 680 series connector.
This is the Farnell web page for the sockets.

**LINK**
I have also found a chasis mounting socket on ebay eBay item number: 362709678935

They are quite expensive so I think I wil try to make some kind of connector to test the scale. When I know it is OK I will fit a different connector to the scale.

Les.

Hi Robin,
After reading this thread I have bought one of these scales from Arc Euro.(500mm) I notice from your other thread on the subject that you made an adapter cable. I thought at first that the connector on the scales was a 7 pin DIN but on checking I found the pin layout was different. I assume that you must have found a source for a 7 pin socket to match the scale. Could you please tell me what it is called and where you managed to obtain it. I think I can fit mine to my Seig X3 without having to shorten it.

Les.

Have a look at this design for a saw table for these band saw that folds out of the way when using the bandsaw horizontally.

Les.

Hi Neil,
I came across an RCD spur box ((Now they seem to call them connection points.) that came with a second hand stair lift I bought for my mother that would drop out if there was a power interruption on the input. I did not know if it was a special that was fitted as some kind of safety feature on stir lifts. I thought it was more of a negative feature as my mother then had to walk up the stairs to reset it. I did think of replacing it with one that did not need reseting after a power loss. (But I never got round to it.)

Les.

If I was cutting a 2.4 mm wide slot I would not use a 2.4 mm cutter even if I had one. I would use a 2mm cutter to cut a slot that would probably be a little over 2mm wide. I would then clean up the sides taking light cuts until the slot was 2.4 mm wide.

Les.

I suspect it could be the centrifugal switch in the motor sticking in the open condition. The click may be the switch dropping back to the closed position. Have a look inside the dewhurst switch and check how many wires (Other than the earth wire.) go between the switch and the motor. If there are only two then the fault is almost certainly in the motor. If there are four then post a diagram of how they are connected to the switch. Do you have a multimeter ? This is so we can get you to do some tests to prove it is not the dewhurst switch. Is the switch a forward - off - reverse switch or just off - on ?

Les.

Do the wires to the original two lights come out at one point in the ceiling or two ?. Also how many wires come out at each point on the ceiling ? There may be more than three wires coming out out of the ceiling. One may be a permanent live which is joint to a wire going to the switch. There could be a third wire joined to this point taking the live feed on to feed something else.

Les.

Edited By Les Jones 1 on 12/04/2020 11:01:20

Sorry for missing those points.

Les.

As the circle is 60' diameter i agree that the wheels are on the same axle does not matter. I am confused as it is a fully functional replica car how you are going to drive the axle. Are you going to machine out the diff housing and use bevel gears so the drive system is similar to the original or is the drive via spur gears or belt to a point close to a wheel ? If it is the second method how can it be considered a replica ?

Les.

Would it not be easier to have the bearings in the wheels and the axle fixed. If it was done that way the hole would not need to be so precise. It could be clamped in position with grub screws. Also if it was to be a working model the wheels should not be locked together.

Les.

They take almost no current so there is no need to use a switching regulator to save power. There is probably noise on the output a the switching frequency. I suggest using using an LM317L linear adjustable regulator and also fitting a few uf tantalum capacitor mounted in a dummy battery in the battery compartment of the calliper.

Les.

They were probably in series as the working voltage of supercapacitors is quite low. (Less than 6 volts from memory.) So the series configuration was probably to get the required voltage.

Les

As John says take some pictures of the inside of the base and tell us if any of the wires from the inside of the motor are connected to anything else such as the on/off switch, mains input cable and capacitor if there is one. I expect there to be three (Or possibly 4 wires wires) coming from inside the motor to the base. If there is no marking on the wires to identify them put some markers on them so that we can identify them when we are telling you what resistance measurements to take.Take a few pictures from slightly different angles so that we can see where wires go without being obscured by other wires. What is the history of the grinder ? For example was it given to you in a dismantled state. Did it stop working and you dismantled it without noting the connections ?

Les.

I too have never heard of " an induction motor with a permanent magnet rotor ". I think Brian's question about it being a 3 phase motor that has been modified needs to be answered.

Les.

I assume that the black wires (U1 & U2) feed the main winding and the red wires feed the auxiliary winding (Via the capacitors on the motor. If this is so then remove both links. Connect wire U1 to terminal U1. Connect wire U2 to terminal U2. Connect wire V1 to terminal V1. Connect wire V2 to W2. Before doing this confirm that the 4 wires are connected as I assume. WITH NO POWER TO THE LATHE confirm that with the forward reverse switch in one position (Forward or reverse. Ignore the off position if it has one.) you get an almost zero resistance reading between wires U1 and V1 and between wires V2 an U2. In the other position you get almost zero resistance V1 and U2 and between V2 and U1. If you do not have a meter I can suggest a method using 4 mains voltage lamps.
If you connect it up and forward and reverse are the wrong way round then swap over wires U1 and U2.

Les.