All posts by EEadmin

Nottingham Gaussfest 2019

Another great High Voltage meet at Papplewick Pumping station this year.

These are some photos and videos from the event.

Derek’s Coils and Stuff…

Extreme kits mini Wimshurst powers a ping pong accelerator


Large Wimshurst throws some sparks

Steve’s Tesla Coil

Roger’s VDG, Geissler tubes and Wimshurst

Van De Graaff with a charged ball

Alec’s Collection


Dave’s Coils

Andrew’s collection

Roberts stuff
3 phase Jacobs ladder


Gary’s Jacobs ladder & Flyback TC

Simon and Mark

Carl’s Tesla coil

Thanks to Andy B and Alex L for many of the above and Mark K for these below.

Please return Its likely I’ll get sent more pics and videos that I’ll post here. (email me tesla@extremelectronics.co.uk if you have a pic or video)

Vigo Tec VG-A4 Writer/Engraver

I wanted to a cheap XY plotter to try some experiments and after looking at ebay I saw an inexpensive plotter to try, the Vigotec VG-A4

Construction was fairly easy, although the only instructions that came with the package were in Chinese. I have since found the instructions here Although due to translation issues, they are not much more help.

The Plotter was constructed and worked first time as a writer using the example JPG’s and the VigoTec Writer Software. (Downloadable here )

Be careful about belt tightness. If the belt it too tight you will easily loose position when moving. Otherwise the hardware is well made an designed.

I haven’t yet tried the Engraver software as this involved changing the firmware in the driver board.

All working well, I started to try driving the plotter by G-Code. There is of course Zero Documentation.

So after a lot of trying things I found the PenUP/Pen Down commands which are M03 and M05 respectively. You will need a delay for the pen server to do its thing, Im currently using G4 P1000 to give a 1 second delay.

This mostly works, as a test I put in a move G1 X Y Z and a pen down followed by a pen up. I did this 4 times to create a dot in each corner of a square, The pen only responded to two of them, I have no idea why.

The Writing software is very buggy. With many of the adjustments not working at all. I also find that you MUST do a pen down then a pen reset before using G-Code otherwise the pen wont work at all. (The pen UP button appears to do nothing. Unless you have loaded an image).

Be careful using G0 the plotter appears to lose position even with the lightest of pens. To cure this and especially if you are using anything heavier, use a G1 X Y Z FXXXX to set the feed rate. ( When using G-Code the speed slider is ignored)

There are some issues with G1 and pen up/down, but I haven’t fully discovered what the causes to these are or any solutions yet.

Tesla Coil Talk at Leeds Uni

7.00 pm Wednesday 13th February 2019
Free tea, coffee and biscuits from 6:30pm
University of Leeds, Michael Sadler Building, Rupert Beckett Lecture Theatre



A general talk on Tesla coils, from the original spark gap tesla coils that would be recognised by Nicola
Tesla, to modern day computer controlled electronic tesla coils. Briefly discussing the various types of tesla
coil, their history, use, construction and design challenges with demonstrations.

Details in the PDF below.

Makers book of ideas

I have for a number of years had a book that I put in notes for making ideas or mad stuff that I don’t have time for. The idea is that I come back to them at a later date. I hadn’t used it for a while and it had got pretty dog eared. So time for an upgrade.

I cust out some shapes based loosely on the XCKD Hazard symbol https://xkcd.com/2038/ for Radioactive High-Voltage Laser-Emitting Biohazards that coat the floor and make it slippery.  (seams to fit) and the skull and crossed spanners.

and glued them to the front of the book

When that had dried I covered the book cover and cut pieces in a contact adhesive

And a piece of thin leather

I waited until the glue was touch dry and pressed the leather over the front cover. With a damp cloth forcing the leather into the corners.

The build was made harder by the fact I was using reclaimed leather from an old jacket, and none of the pieces were quite big enough. This explains the problem at the top right corner. Covered up in the end with another strip of leather top to bottom on the Right hand side. (not too happy about that) The back was also covered in a single piece of leather attached with contact adhesive.

The spine needed covering, (again because I couldn’t recover big enough pieces. ) so I made a narrow strip of leather with the edges folded in and glued this along the spine.

Finished book


MSF Clock be wrong – RPI MSF transmitter

A friend of mine was asking me about MSF time reception and I realised I only knew some of the basics.  So this sent me on  a hunt for more information.

In the UK the MSF tme signal is sent on a carrier of 60khz from a transmitter in Anthorn Yorkshire with a radiated power if 17KW   http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal

17KW sounds large, but this is at 60 Khz, the efficiency of ariels less than 2.5Km (a half a wavelength of 60Khz) long with all round  coverage is going to be much less than 1, probably a lot less than 1. The old Time Signal transmitter at Rugby was in the order of 200KW. I can only assume the new transmitter is of a similar power to get a ERP of 17Kw.

After a little looking around, I discovered the web site of Andy (http://www.burningimage.net/msfsimulator) who has made a MSF transmitter for 60Khz using a Pc’s sound card using the third harmonic of 20Khz to produce a 60 Khz signal and written the Python code to encode a date time into the MSF protocol.

So with most of the heavy lifting done, I started to think about what I had to hand. Raspberry Pi’s…

My first thought was using the frequency generator built in to the PI to give the 60Khz as used in many PI transmitter projects , but  there were limitations in trying to get 60Khz. So the next thought was a PWM output. A bit of googling gave me the formulae for the frequency of the hardware PWM on a PI

pwmClockDivisor=19200000/PWMRange/Freq

PWMrange is the number of “levels” you can specify for the PWM signal.

After some experimenting I found that you could set the range really small e.g. 2 Which is great if you sent the PWM a 0  it goes off. If you send it a 1 you get 50/50 Mark Space, ideal.  Setting the pwmClockDivisor to 160 gives a 60Khz output.

The Wiring PI Wrapper for Python supports this setup. So setting  the hardware PWM is a case of

io = wiringpi.GPIO(wiringpi.GPIO.WPI_MODE_PINS)
io.pinMode(PIN,io.PWM_OUTPUT)
io.pwmSetClock(160)
io.pwmSetRange(2)

The wiring Pi for Python setup is detailed here http://raspi.tv/how-to-install-wiringpi2-for-python-on-the-raspberry-pi

#-------------------------------------------------------------------
# This script uses PWM on GPIO PIN 18 to transmit an MSF timecode
#
# Save it as msf.py somewhere on your Pi.
#
# Run it with 'python msf.py'
#
# Requires the Wiring Pi Python Library
#
# Based on Audio MSF code from 
#
# http://www.burningimage.net/msfsimulator
# by
# andy@burningimage.net
#
# PWM output, Frequency and DateTime Code Added by Derek Woodroffe 
# tesla@extremeelectronics.co.uk
#-------------------------------------------------------------------

#-------------------------------------------------------------------
# Set the time/date to transmit below.
#
# The date time startes at the datetime you set regardless of local 
# clock settings
#
# Use groundhogday=True to repeat the same "day" every 24 hours.
# 
# Your clock(s) should have set its time by around minute 5.
# Some clocks only look at MSF data every 12 hours.
#
# The day of the week is automatically set to the correct value
#-------------------------------------------------------------------

import time
import math
import wiringpi
import datetime

#----------------- Carrier  Frequency ------------------------------
#UK tested, others un-tested not sure about the modulation
Freq=60000 #60Khz UK/Japan - 66.66Khz Russia - 77.5Khz Germany/Taiwan

#----------------------- Set inital time ---------------------------
#start with a defined datetime
mmfdt = datetime.datetime(2019,4,1  ,6,1) #datetime year,month,day,hour,min
#Run with current time 
#mmfdt = datetime.datetime.now() 
#run 1 hour in the future
#mmfdt = datetime.datetime.now()+datetime.timedelta(0,0,0,0,0,1,0) #timedelta([days[, seconds[, microseconds[, milliseconds[, minutes[, hours[, weeks]]]]]])

#------------------------ Groundhogday -----------------------------
#repeat after 24 hours.
#groundhogday=True
#dont repeat 
groundhogday=False

#------------------------ Parity -----------------------------------
# Set to 1 to transmit proper parity bits
enableparity = 1
#-------------------------------------------------------------------


def carrier_on(length):
    io.pwmWrite(PIN,1)
    time.sleep(0.001*length)
    
def carrier_off(length):
    io.pwmWrite(PIN,0)
    time.sleep(0.001*length)

def minutemarker():
    carrier_off(500)
    carrier_on(500)
    
def send01():
    carrier_off(100)
    carrier_on(100)
    carrier_off(100)
    carrier_on(700)

def send11():
    carrier_off(300)
    carrier_on(700)

def send00():
    carrier_off(100)
    carrier_on(900)

def send10():
    carrier_off(200)
    carrier_on(800)

bcdlist= [80, 40, 20, 10, 8, 4, 2, 1]

#setup PWM GPIO pin 18 (pin1) Hardware PWM at Freq
PIN=1
#pwmClock divisor=19.2e6/2/Frequency
pwmClock=19200000/2/Freq

io = wiringpi.GPIO(wiringpi.GPIO.WPI_MODE_PINS)
io.pinMode(PIN,io.PWM_OUTPUT)
io.pwmSetClock(pwmClock)
io.pwmSetRange(2)
io.pwmWrite(PIN,0)

mmfdts=mmfdt

while(True):
    year = mmfdt.year
    month = mmfdt.month
    dayofmonth = mmfdt.day
    dayofweek = (mmfdt.weekday()+1) % 7       #0 = sunday, 1 = monday etc.
    hour = mmfdt.hour
    minute= mmfdt.minute

    # Ignore the '0' element in the list as it confuses matters
    # with the timecode
    timecodeA = [0] * 60
    timecodeB = [0] * 60

    # Convert the year to BCD and store in the correct place in the timecode
    bcdindex=0
    temp = year
    sum=0
    for i in range(17,25):
        if temp >= bcdlist[bcdindex]:
            timecodeA[i] = 1
            sum += 1;
            temp -= bcdlist[bcdindex]
        bcdindex += 1

    # Work out the parity bit for 17-24
    if (sum % 2) != 1:
        timecodeB[54] = enableparity

    # Now do the month
    bcdindex=3  #starts at 10
    temp = month
    sum = 0
    for i in range(25,30):
        if temp >= bcdlist[bcdindex]:
            timecodeA[i] = 1
            temp -= bcdlist[bcdindex]
            sum += 1
        bcdindex += 1

    # Do the day of month
    bcdindex=2  #starts at 20
    temp = dayofmonth
    for i in range(30,36):
        if temp >= bcdlist[bcdindex]:
            timecodeA[i] = 1
            temp -= bcdlist[bcdindex]
            sum += 1
        bcdindex += 1

    # Work out the parity bit for 25-35
    if (sum % 2) != 1:
        timecodeB[55] = enableparity

    # Do the day of week
    bcdindex=5  #starts at 4
    temp = dayofweek
    sum = 0
    for i in range(36,39):
        if temp >= bcdlist[bcdindex]:
            timecodeA[i] = 1
            temp -= bcdlist[bcdindex]
            sum += 1
        bcdindex += 1

    # Work out the parity bit for 36-38
    if (sum % 2) != 1:
        timecodeB[56] = enableparity

    # Do the hour
    bcdindex=2  #starts at 20
    temp = hour
    sum = 0
    for i in range(39,45):
        if temp >= bcdlist[bcdindex]:
            timecodeA[i] = 1
            temp -= bcdlist[bcdindex]
            sum += 1
        bcdindex += 1

    # Do the minute
    bcdindex=1  #starts at 40
    temp = minute
    for i in range(45,52):
        if temp >= bcdlist[bcdindex]:
            timecodeA[i] = 1
            temp -= bcdlist[bcdindex]
            sum += 1
        bcdindex += 1

    # Work out the parity bit for 36-38
    if (sum % 2) != 1:
        timecodeB[57] = enableparity

    #Bits 53A - 58A should always be 1
    for i in range(53,59):
        timecodeA[i] = 1

    print(str(year).zfill(2) + "-" + str(month).zfill(2) + "-" + str(dayofmonth).zfill(2) + " " + str(hour).zfill(2) + ":" + str(minute).zfill(2)+ " - " + str(dayofweek)  )
    #print("A bits: " + str(timecodeA[1:]))
    #print("B bits: " + str(timecodeB[1:]))

    # Now play the timecode out
    minutemarker()
    for i in range(1,60):
        if (timecodeA[i] == 1) and (timecodeB[i] == 1):
            send11()
        elif (timecodeA[i] == 0) and (timecodeB[i] == 1):
            send01()
        elif (timecodeA[i] == 0) and (timecodeB[i] == 0):
            send00()
        elif (timecodeA[i] == 1) and (timecodeB[i] == 0):
            send10()

    mmfdt = mmfdt + datetime.timedelta(0,60) #timedelta([days[, seconds[, microseconds[, milliseconds[, minutes[, hours[, weeks]]]]]]])
    
    if (groundhogday):
      if (mmfdt-mmfdts>datetime.timedelta(1)):
        #restart day
        mmfdt=mmfdts
        print ("RESTART DAY")

Then

io.pwmWrite(PIN,1) turns on the 60 Khz and io.pwmWrite(PIN,0) turns it off.

I replaced all of Andy’s Sound Card Code with functions that mimicked the operation, but used the PWM commands above and a sleep to give me the correct on/off times (yes, sleep is inaccurate, this could be improved)

Adding a short wire to GPIO 1 (PIN18) and placing this near an MSF clock, worked… (it was 4 in the afternoon, and not April 1st 2019)

But if you want some fun, this close is probably not enough 🙂

Note: Transmitting on this frequency is Illegal and It is possible to affect all sorts of equipment that uses MSF. The transmitter below has a range of only a few feet and so is unlikely to cause any unexpected effects, but don’t do this where there is  any medical or industrial control equipment that may use the time signal.

Oh, and your neighbour may get quite miffed if his alarm clock goes off at the wrong time…

So adding some power..

I made an X of 300mm strips of MDF and wound 100Turns of 0.3mm enamelled wire around the structure.

This I drove from a MC4428 mosfet driver. Using both channels together gives a full bridge drive of up to 1.5A and can run up to 24V.

C1 will need to be modified to get your coil in tune. Tuning can easily be done by monitoring the Cap to coil connection and varying the value of C1 for maximum voltage. Beware that the voltage on C1 can get to about 100V when in tune, so keep it away from your PI#s GPIO

(And other things too)

The Circuit generates about 1W of power, but remember the ariel is only a fraction of the 2.5Km dipole required for 1:1 ERP , so the actual  ERP is much lower. Mine will “correct” clocks time at a range of about 4-5 Meters.

 

Key-In-The-Dark Torch

Key in the dark has been played in Scout groups and youth groups for as long as I can remember.

The idea of the game is one Scout is blindfolded and sat on a chair with a large set of keys underneath. He is “armed” with a torch. Usually a number of obstacles and places to hide are set up around them.  The rest of the scouts need to stealthily get to the keys without the Scout shining the torch on them.  If they are hit by a touch beam they are defined dead and have to either sit out the game, or start from the beginning again. The idea is that any sound made by the scouts in their approach means a torch shone their way.

Of course in practice a torch is not the ideal “weapon” although rules are that the torch is only to be used intermittently, it is basically an infinite resource and is usually shone around with abandon. Plus the operator being blindfold, they have no idea if the touch is on or off. The other main problem is that the torch beam diverges so much that multiple asalients can be cought at once.

So I started to look at alternatives. As 5W leds are cheap I thought of one of these as a source, combined with a 10 x 70mm focal length lens from a watchmakers eyeglass (loupe) in a 20mm tube. I could get a pretty narrow, bright beam.

Mounting the LED on a piece of copper allowed for any heat from the led to escape. 

Of course, I needed a way of switching this, so I used a MC4427 1.5A mosfet driver, purely as it was a single chip solution and mainly as I had one to hand.

I dead bug soldered it, as there were only 4 connections. and glued the driver to the back of the heatsink.

I had had the idea of “charge” to keep down the number of flashes, the idea being that every press of the button would freeze out the user for 0.5 Seconds. To show this, I thought of a number of neopixels along the barrel. So these were attached with some acrylic rings to spread the light out 

Whilst I was thinking about the design of this, I was given an Adafruit Feather Huzzah 

This was ideal, as it had a Lipo PSU and charger built in, and plenty of IO, coupled with a 25mmx9mm LIPO battery it gives loads of power..

Plus If you use MicroPython you got the neopixel support.

Realising that the operator would be blindfolded, I wanted some feedback so they would know when the torch was used. After trying a solenoid, I found this had two problems. 1. It was power hungry. 2. It took up a load of space.  So I went back to a large’ish vibration motor (also to hand)

I had decided that the whole thing should fit in a tube no more than 40mm in diameter, so I laser cut some supports and hung the whole lot from two m3 threaded bars. After many attempts I finally got the acrylic into pieces that would support the electronics and battery and assembled the whole thing together. 

 

Of course, I’d forgotten the buttons. These needed to be at the front, but so the case could be removed they needed to connect at the back.

After a couple of attempts with internal wiring, that got cought up either putting it together or taking it apart. I eventually put the wires on the outside, covered the whole handle, wires and everything in leather and connected the buttons with a cable at the back.

The USB cable for power (and programming) currently exits out of the back, but is soon to be replaced with a micro socket.  There is also a small switch for the units power.

The next addition was a burst fire mode, you get 5 shots in quick succession, but it takes longer to recharge.

I also added an auto power off, if left for 60 seconds.

Circuit Diagram 

Download (SVG, 21KB)

Final Touches…

End plate with USB charging port and On off switch.

Unfortunately as I take the power for the motor, Neopixels and the main LED straight from the battery Powering down is a two stage process. First you press and hold both buttons. After a few seconds everything is turned off. Then you can switch off the uP. I do it this way as  I don’t have to switch everything on to charge it.

The finished Torch

Code


import machine, neopixel, time, utime

np1 = neopixel.NeoPixel(machine.Pin(12), 8)
np2 = neopixel.NeoPixel(machine.Pin(13), 8)
LED5w = machine.Pin(14, machine.Pin.OUT)
B1 = machine.Pin(5, machine.Pin.IN, machine.Pin.PULL_UP)
B2 = machine.Pin(2, machine.Pin.IN, machine.Pin.PULL_UP)
vib = machine.Pin(4, machine.Pin.OUT)

LED5w.off()

firec=(255,255,255)
chargec=(0,20,0)
black=(0,0,0)

OffTime=60

def fire(fx):
   for x in range(0,fx,1):
      for a in range(8):
        np1[a]=firec
        np2[a]=firec
        np1.write()
        np2.write()
        time.sleep_ms(4)
        np1[a]=black
        np2[a]=black
        np1.write()
        np2.write()
      LED5w.on()
      vibrate()
      time.sleep_ms(100)
      LED5w.off()
  
def charge(cx):
  for a in range(8):
    np1[a]=chargec
    np2[a]=chargec
    np1.write()
    np2.write()
    time.sleep_ms(cx)
  
def vibrate():
  vib.value(1)
  time.sleep_ms(70)
  vib.value(0)


charge(63)
start=utime.ticks_ms()

while(B1.value() or B2.value()):
  if not B1.value():
    fire(1)
    start=utime.ticks_ms()
    charge(63)
    if(not B1.value()): 
      time.sleep_ms(1000) 
    
  if not B2.value():
    fire(5)
    start=utime.ticks_ms()
    charge(350)
    if(not B2.value()): 
      time.sleep_ms(3000) 
    
  if ((utime.ticks_ms()-start) > OffTime*1000):
    for a in range(7,-1,-1):
        np1[a]=black
        np2[a]=black
        np1.write()
        np2.write()
        time.sleep_ms(50)
    np1[0]=(0,0,10)
    np1.write()
    while(B1.value()):
        time.sleep_ms(200)
    start=utime.ticks_ms()        
    charge(63)


vibrate()
for a in range(7,-1,-1):
  np1[a]=black
  np2[a]=black
  np1.write()
  np2.write()
LED5w.off()




Nottingham Gaussfest 2018

What a great day at Papplewick Pumping station. The change of venue caused some teething problems with space and I caused some problems with exhibitors names (no change there!) Over 140 visitors, three film crew’s on the day and 12 Exhibitors.

 

The pumping station were great in sorting out our rather strange needs and were over the moon about the attendance (they ran out of bacon in the cafe, apparently the indication of a good day). All proceeds from the day went directly to the Pumping station.

Photos from the day, If you, or your equipment is missing, please email me a picture/video. It was such a busy day I missed a lot of things.

Derek’s (my) Equipment

Sam’s Equipment

Tony/Leicester Hackspace

Alex’s Equipment

Dave’s Equipment

Jason’s Equipment

Roger’s Equipment

Chris’s Equipment

Chris with his Florescent tubes and small radio

Chris’ Battery powered Tesla coil

Andrews Equipment

Earl

After a number of valiant attempts and a few disasters. Earl unfortunately failed to get his coil working. This was a great shame as the travel and effort he put in was huge. I would have loved to see his coil in action again. I especially wanted to see his bottle cap bank in action.

Robert’s Jacobs ladder


Groups

Papplewick Pumping station

A superb venue, although a bit cold, mitigated by a superb on site Cafe…