Member postings for John Haine

The Uniport is I think a parallel port BoB which also needs a USB connection to get +5v from the host. Mach3 needs a 32 bit processor to drive a parallel port, any 64 bit processor can only use a USB or Ethernet interface to a suitable motion controller. PCs with a parallel port must be pretty rare these days. However a USB motion controller such as the UC100 could be used with this to drive the parallel port input.

Mach 3 is OK but any new user would be well advised to use Mach4 or UCCNC or similar with a USB or Ethernet interface.  M3 is long in the tooth and unsupported for getting on for 10 years.

Edited By John Haine on 08/08/2023 13:40:45

Y often serves as a vowel depending on context as Bing would probably tell you

Or Wikipedia.

Well, sine ALL the energy in the tides is already dissipated by hydrodynamic friction with the land we are already doomed!

Make/model/spec? Usually the interface just expects to see quadrature logic signals but the devil is in the detail.

Dave, you could surely use software serial with the pP and get the Nano to gather data from a BME280 via I2C? It would then have much less time-critical software to run.

The only disadvantage of PICPET is the chip can't be programmed to do anything else: it can only be a Precision Event Timer. Otherwise, they are the bees knees.

True - but then they are only a PIC microcontroller, cheap as chips, and the code is in the public domain. Just a serial interface into a host needed.

I mean that if you deliver period measurements, for example, instead of trying to send optointerrupter on/off signals, then latency should not be a bother. Of course, that means that you must be satisfied with the way those period measurements are made, and that may require another module if you want to do it in a particularly-accurate way, but many such modules are also postage-stamp sized. (BTW, I am not promoting ESP32's and have never used one; it's just an example.)

My approach is to use a picPET07 driven by a 10MHz OCXO to time both edges of the pendulum pulse. Far more accurate than an Arduino can achieve. (In answer to your question about timing approach.) The OCXO takes 5V 300mA continuous to keep its heater on, more like 500mA on startup. That would make it the largest consumer of power in the clock. Also ideally needs a linear regulator which assuming a primary supply of 12V (to give headroon for the escapement drive) gets rather hot! And if the Pi is in the case too it doubles the supply requirement again.

The clock will need mains power and battery backup. I've already done this in another clock so quite familiar with the approach - but putting the OCXO and the Pi in the case means a much bigger battery.

My experience with a headless Pi with WiFi connectivity for logging is not good - they have a habit of dropping off the WiFi and need resetting to recover which stops the log. I prefer to have an MMI on the Pi and map a folder to my Windows file system for data transfer.

I would obviously do some measurements on the 433MHz Tx/Rx to see how they perform - one should arrive soon. Cheap as chips.

Um... Please explain?

Planning to complete the build of my new clock, I'm thinking about instrumentation. The clock will be located in a fairly prominent position in our living room, and I have a friend who will make a nice looking case for it. I would like to monitor its running but I don't really want to have a Raspberry Pi with its accoutrements hanging round it or taking more space in the case. It did occur to me that it would be easy to make the pendulum pulses drive one of the low-cost 433MHz telemetry transmitters so I could have the monitoring kit elsewhere in the house. These use on-off keying so should be pretty deterministic.

Does anyone have any experience of using these for this sort of application please, or have ideas for an alternative? Bluetooth has been suggested but its protocol will have variable delays.

When that happened on a Citroen I had part of the filler cap fell into the tank!

Actually though I always re-home the X axis on the lathe on startup it's usually within a fraction of a mm, which I put down to the non-integer whole step being lost when the drivers power down. I only re-home to make sure my tool offsets give the right diameter.

Likewise on the mill, I generally find that on power up the actual position of the spindle closely corresponds to the DROs, though I generally re-reference to the new workpiece. When I was doing a lot of rotary axis stuff doing CNC knurling where the Y axis is referenced to zero along the rotary axis, I found that the Y axis setting was preserved when powering down and up again. I very rarely "home all" as apart from giving a reference for soft limits it has no useful function. I do all my work by referencing to the workpiece.

I can't quite see why they think it is so important to make the frame rigid. Surely the blade should be mounted to cut on the pull stroke, for which the frame is only needed to hold the "far end" in the right place? I always thought that "junior hacksaws" were a waste of time until I tried putting in the blade "backwards"...

**LINK**

They had to work very hard to get that patent and it's so specific to the construction that it's probably not worth the paper it's written on.

Leaving aside whether the drives are properly configured, do you mean referencing or homing? The only axis I "home" on my lathe is the "real" X axis (i.e. radial) so I can use tool offsets. I always "reference" the Z axis off the end of the workpiece (cf the surface when milling), as there could be various chucks and variable "stickout" depending on what I'm doing. I have a tool contact sensor to do this.  So, to be clear, program coordinate Z = 0 is the end of the material. 

Edited By John Haine on 31/07/2023 17:10:26

Agreed. But drive the worm from a stepper.

Just fit a stepper motor and Ward controller and forget about plates.

Yes, consistently constant.

I don't think you will need a core at all. , the required force is minimal and a core just creates an attractive force with the magnets that will perturb the pendulum.

You may have seen the "magnet in a coil" in one of Ned Bigelow's 2-pendulum designs.

By the way, though a core may not change the field it does change the flux! It's flux that generates the force.

As for bobbin shape, look at Bigelow's design.  But I think you want a solenoidal coil considerably longer than the magnet and the magnet should be central when impulsed.

Edited By John Haine on 28/07/2023 18:38:57

I though they gave more information but there just seems to be this paragraph:

"Preliminary experiments have been made with this spring arrangement on an electrically driven pendulum without barometric correction,and no change in rate could be detected for a change in total amplitude of about one half inch. Such a change in amplitude caused more than a second a day change in rate before the spring was connected. The
accuracy of measurement was to about 0.01 sec. by comparison with time signals from WWV by means of an oscilloscope."

Yes, Bush and Jackson report test results. I'll post them later.

Oops! Apologies both.